Grid plan
Overview
 
The grid plan, grid street plan or gridiron plan is a type of city
City
A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...

 plan in which street
Street
A street is a paved public thoroughfare in a built environment. It is a public parcel of land adjoining buildings in an urban context, on which people may freely assemble, interact, and move about. A street can be as simple as a level patch of dirt, but is more often paved with a hard, durable...

s run at right angles to each other, forming a grid. In the context of the culture of Ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, the grid plan is called Hippodamian plan.
The grid plan dates from antiquity and originated in multiple cultures; some of the earliest planned cities were built using grid plans.

By 2600 BC, Mohenjo-daro
Mohenjo-daro
Mohenjo-daro is an archeological site situated in what is now the province of Sindh, Pakistan. Built around 2600 BC, it was one of the largest settlements of the ancient Indus Valley Civilization, and one of the world's earliest major urban settlements, existing at the same time as the...

 and Harappa
Harappa
Harappa is an archaeological site in Punjab, northeast Pakistan, about west of Sahiwal. The site takes its name from a modern village located near the former course of the Ravi River. The current village of Harappa is from the ancient site. Although modern Harappa has a train station left from...

, major cities of the Indus Valley Civilization
Indus Valley Civilization
The Indus Valley Civilization was a Bronze Age civilization that was located in the northwestern region of the Indian subcontinent, consisting of what is now mainly modern-day Pakistan and northwest India...

 (present day Pakistan), were built with blocks divided by a grid of straight streets, running north-south and east-west.
Encyclopedia
The grid plan, grid street plan or gridiron plan is a type of city
City
A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...

 plan in which street
Street
A street is a paved public thoroughfare in a built environment. It is a public parcel of land adjoining buildings in an urban context, on which people may freely assemble, interact, and move about. A street can be as simple as a level patch of dirt, but is more often paved with a hard, durable...

s run at right angles to each other, forming a grid. In the context of the culture of Ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, the grid plan is called Hippodamian plan.

Ancient grid plans

The grid plan dates from antiquity and originated in multiple cultures; some of the earliest planned cities were built using grid plans.

By 2600 BC, Mohenjo-daro
Mohenjo-daro
Mohenjo-daro is an archeological site situated in what is now the province of Sindh, Pakistan. Built around 2600 BC, it was one of the largest settlements of the ancient Indus Valley Civilization, and one of the world's earliest major urban settlements, existing at the same time as the...

 and Harappa
Harappa
Harappa is an archaeological site in Punjab, northeast Pakistan, about west of Sahiwal. The site takes its name from a modern village located near the former course of the Ravi River. The current village of Harappa is from the ancient site. Although modern Harappa has a train station left from...

, major cities of the Indus Valley Civilization
Indus Valley Civilization
The Indus Valley Civilization was a Bronze Age civilization that was located in the northwestern region of the Indian subcontinent, consisting of what is now mainly modern-day Pakistan and northwest India...

 (present day Pakistan), were built with blocks divided by a grid of straight streets, running north-south and east-west. Each block was subdivided by small lanes. The cities and monasteries (e.g. Julian, Takht Bahi etc) of "Taxila Civilization" or "Ghandhara Civilization" (in modern day Pakistan) dating back to 1st millennium BCE to the 11th century CE, also had grid-based design. Islamabad, the capital of Pakistan, since 1959, was also founded on the grid-plan of the near-by Taxila ruined city of "Sirkhap".

A workers' village at Giza, Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

 (2570-2500 BC) housed a rotating labor force and was laid out in blocks of long galleries separated by streets in a formal grid. Many pyramid-cult cities used a common orientation: a north-south axis from the royal palace east-west axis from the temple meeting at a central plaza where King and God merged and crossed.

Hammurabi
Hammurabi
Hammurabi Hammurabi Hammurabi (Akkadian from Amorite ʻAmmurāpi, "the kinsman is a healer", from ʻAmmu, "paternal kinsman", and Rāpi, "healer"; (died c...

 (17th century BC) was a king of the Babylonian Empire
Babylonia
Babylonia was an ancient cultural region in central-southern Mesopotamia , with Babylon as its capital. Babylonia emerged as a major power when Hammurabi Babylonia was an ancient cultural region in central-southern Mesopotamia (present-day Iraq), with Babylon as its capital. Babylonia emerged as...

 who made Babylon
Babylon
Babylon was an Akkadian city-state of ancient Mesopotamia, the remains of which are found in present-day Al Hillah, Babil Province, Iraq, about 85 kilometers south of Baghdad...

 one of the greatest metropolises in antiquity
Ancient history
Ancient history is the study of the written past from the beginning of recorded human history to the Early Middle Ages. The span of recorded history is roughly 5,000 years, with Cuneiform script, the oldest discovered form of coherent writing, from the protoliterate period around the 30th century BC...

. He rebuilt Babylon, building and restoring temples, city walls, public buildings, and building canals for irrigation. The streets of Babylon were wide and straight, intersected approximately at right angles, and were paved with bricks and bitumen.

The tradition of grid plans is continuous in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 from the 15th century BC onward in the traditional urban planning
Ancient Chinese urban planning
Ancient Chinese urban planning is the application of the traditional principles of Chinese architecture to urban design. These traditions can be summarized as: fengshui geomancy and astronomy; the well-field system; gaitian cosmology; qi as a medium of energy connecting man, earth, and heaven;...

 of various ancient Chinese states. Guidelines put into written form in the Kaogongji
Kaogongji
Kaogong ji or The Records of Examination of Craftsman, sometimes translated as Book of Diverse Crafts, is a classic work on science and technology in Ancient China, compiled towards the end of the Spring and Autumn Period.- External links :...

 during the Spring and Autumn Period (770-476 BC) stated: "a capital city should be square on plan. Three gates on each side of the perimeter lead into the nine main streets that crisscross the city and define its grid-pattern. And for its layout the city should have the Royal Court situated in the south, the Marketplace in the north, the Imperial Ancestral Temple in the east and the Altar to the Gods of Land and Grain in the west."

Teotihuacan
Teotihuacan
Teotihuacan – also written Teotihuacán, with a Spanish orthographic accent on the last syllable – is an enormous archaeological site in the Basin of Mexico, just 30 miles northeast of Mexico City, containing some of the largest pyramidal structures built in the pre-Columbian Americas...

, near modern-day Mexico City
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...

, is the largest ancient grid-plan site in the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

. The city's grid covered eight square miles.

Roman Grid

Perhaps the most well-known grid system is that spread through the colonies of the Roman Empire. The idea of the archetypal Roman Grid
Roman centuriation
Centuriation was a field system used by the Romans for land division. It developed from the system used earlier for laying out castra and in the founding of new cities....

 was introduced to Italy first by the Greeks, with such information transferred by way of trade and conquest.

Although the grid was an idea present in Hellenic societal and city planning, it was not pervasive prior to the 5th century BC. However, it slowly gained primacy through the work of Hippodamus of Miletus, who slowly planned and replanned many Greek cities in accordance with this form. The concept of a grid being the ideal method of town-planning became widely accepted by the time of Alexander the Great. His conquests were a step in the propagation of the grid plan throughout colonies, some as far-flung as Taxila in Pakistan, that would later be mirrored by the expansion of the Roman Empire. The Greek grid had its streets aligned roughly in relation to the cardinal points and generally looked to take advantage of visual cues based on the hilly landscape typical of Greece and Asia Minor. This was probably best exemplified in Priene
Priene
Priene was an ancient Greek city of Ionia at the base of an escarpment of Mycale, about north of the then course of the Maeander River, from today's Aydin, from today's Söke and from ancient Miletus...

, in present-day western Turkey, where the orthogonal city grid was laid out according with respect to the cardinal points, on sloping terrain that struck views out towards a river and the afore-mentioned city of Miletus
Miletus
Miletus was an ancient Greek city on the western coast of Anatolia , near the mouth of the Maeander River in ancient Caria...

.

The Etruscan people, whose territories encompassed what would eventually become Rome (Rix cited in Woodward 2008), founded what is now the Italian city of Marzabotto at the end of the 6th century BC. It was based on Greek Ionic ideas, and it was here that the main east-west and north-south axes of a town (the decumanus maximus and cardo maximus respectively) could first be seen in Italy. According to Stanislawski, there is little evidence that the Romans adopted the Etruscan model at Marzabatto early in their expansion. Instead, the Roman Grid
Roman centuriation
Centuriation was a field system used by the Romans for land division. It developed from the system used earlier for laying out castra and in the founding of new cities....

 was spread around the Mediterranean and into northern Europe later on during “the late Republic and the early Empire” period that saw dissemination of the grid plan throughout this area.
The military expansion of this period facilitated the grid form becoming the standard, as Romans established “castra
Castra
The Latin word castra, with its singular castrum, was used by the ancient Romans to mean buildings or plots of land reserved to or constructed for use as a military defensive position. The word appears in both Oscan and Umbrian as well as in Latin. It may have descended from Indo-European to Italic...

” firstly as military centres in their territories, some of which would develop into administrative hubs as well. Despite being similar in form to the Greek version of a grid, the Roman grid was ultimately designed on the basis of being practical. Firstly, Roman castra were often sited on flat land, especially in close proximity to or on important nodes like river crossings or intersection trade routes. The dimensions of the castra were often standard as well, with each of its four walls generally having a length of 2150 feet. Familiarity was the aim of such a standard form of town planning. As soldiers could be stationed anywhere around the Empire, way-finding would be a non-issue within established towns as there would be no variation from place to place. All would have the afore-mentioned decumanus maximus
Decumanus Maximus
In Roman city planning, a decumanus was an east-west-oriented road in a Roman city, castra , or colonia. The main decumanus was the Decumanus Maximus, which normally connected the Porta Praetoria to the Porta Decumana .This name comes from the fact that the via decumana or decimana In Roman city...

 and cardo maximus at its heart, the intersection of which would form the forum. Around this intersection would be sited important public buildings in much the same way a Central Business District sits at the centre of modern day metropolitan areas. Indeed, such was the level of familiarity between towns that Higgins states soldiers “would be housed at the same address as they moved from castra to castra”. Pompeii has been cited by both Higgins and Laurence as the best preserved example of the Roman grid.

Outside of the castra, large tracts of land were also divided in accordance with the grid within the walls. These were typically 2400 feet per side (called in Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 centuria
Ancient Roman units of measurement
The ancient Roman units of measurement were built on the Hellenic system with Egyptian, Hebrew, and Mesopotamian influences. The Roman units were comparatively consistent and well documented.-Length:Notes...

), and contained 100 parcels of land (each called in Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 heredium
Ancient Roman units of measurement
The ancient Roman units of measurement were built on the Hellenic system with Egyptian, Hebrew, and Mesopotamian influences. The Roman units were comparatively consistent and well documented.-Length:Notes...

). The decumanus maximus and cardo maximus extended from the town gates out towards neighbouring settlements. These were lined up to be as straight as possible, only deviating from their path due to natural obstacles that prevented a direct route.

While the imposition of only one town form regardless of region could be seen as an imposition of imperial authority, there is no doubting the practical reasoning behind the formation of the Roman grid. Under Roman guidance, the grid was designed for efficiency and inter-changeability, both facilitated by and aiding the expansion of their empire.

Asia from the first millennium AD

As Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and the Korean peninsula
Korean Peninsula
The Korean Peninsula is a peninsula in East Asia. It extends southwards for about 684 miles from continental Asia into the Pacific Ocean and is surrounded by the Sea of Japan to the south, and the Yellow Sea to the west, the Korea Strait connecting the first two bodies of water.Until the end of...

 became politically centralized in the 7th century AD, those societies adopted Chinese grid-planning principles in numerous locations. In Korea, Gyeongju
Gyeongju
Gyeongju is a coastal city in the far southeastern corner of North Gyeongsang province in South Korea. It is the second largest city by area in the province after Andong, covering with a population of 269,343 people according to the 2008 census. Gyeongju is southeast of Seoul, and east of the...

, the capital of Unified Silla
Unified Silla
Unified Silla or Later Silla is the name often applied to the Korean kingdom of Silla, one of the Three Kingdoms of Korea, when it conquered Baekje in 660 and Goguryeo in 668, unifying the southern portion of the Korean peninsula...

, and Sanggyong, the capital of Balhae
Balhae
Balhae was a Manchurian kingdom established after the fall of Goguryeo. After Goguryeo's capital and southern territories fell to Unified Silla, Dae Jo-yeong, a Mohe general, whose father was Dae Jung-sang, established Jin , later called Balhae.Balhae occupied southern parts of Manchuria and...

, adapted the Tang Dynasty
Tang Dynasty
The Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...

 Chinese model. The ancient capitals of Japan, such as Fujiwara-Kyô
Fujiwara-kyo
was the Imperial capital of Japan for sixteen years, between 694 and 710. It was located in Yamato Province , having been moved from nearby Asuka. However, in the Nihon Shoki, the name Fujiwara-kyō had never been used...

 (AD 694-710), Nara
Nara, Nara
is the capital city of Nara Prefecture in the Kansai region of Japan. The city occupies the northern part of Nara Prefecture, directly bordering Kyoto Prefecture...

 (Heijô-Kyô, AD 710-784), and Kyoto
Kyoto
is a city in the central part of the island of Honshū, Japan. It has a population close to 1.5 million. Formerly the imperial capital of Japan, it is now the capital of Kyoto Prefecture, as well as a major part of the Osaka-Kobe-Kyoto metropolitan area.-History:...

 (Heian-Kyô, AD 794-1868) also adapted from Tang's capital. However, for reasons of defense, the planners of Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...

 eschewed the grid, opting instead for an irregular network of streets surrounding the Edo Castle
Edo Castle
, also known as , is a flatland castle that was built in 1457 by Ōta Dōkan. It is located in Chiyoda in Tokyo, then known as Edo, Toshima District, Musashi Province. Tokugawa Ieyasu established the Tokugawa shogunate here. It was the residence of the shogun and location of the shogunate, and also...

 grounds. In later periods, some parts of Tokyo were grid-planned, but grid plans are generally rare in Japan, and Japanese addressing system
Japanese addressing system
The Japanese addressing system is used to identify a specific location in Japan. In Japanese, addresses are written using the opposite convention from Western addresses, starting with the biggest geographical entities down to the more specific ones....

 is accordingly based on increasingly fine subdivisions, rather than a grid.

The grid-planning tradition in Asia continued through the beginning of the 20th century, with Sapporo, Japan (est. 1868) following a grid plan under American influence.

Europe and its colonies

New Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an towns were planned using grids beginning in the 12th century, most prodigiously in the bastides
Bastides
Bastides are fortified new towns built in medieval Languedoc, Gascony and Aquitaine during the thirteenth and fourteenth centuries, although some authorities count Mont-de-Marsan and Montauban, which was founded in 1144, as the first bastides...

 of southern France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 that were built during the 13th and 14th centuries. Medieval European new town
New town
A new town is a specific type of a planned community, or planned city, that was carefully planned from its inception and is typically constructed in a previously undeveloped area. This contrasts with settlements that evolve in a more ad hoc fashion. Land use conflicts are uncommon in new...

s using grid plans were widespread, ranging from Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 to the Florentine region. Many were built on ancient grids originally established as Roman colonial outposts.

The Roman model was also used in Spanish settlements during the Reconquista
Reconquista
The Reconquista was a period of almost 800 years in the Middle Ages during which several Christian kingdoms succeeded in retaking the Muslim-controlled areas of the Iberian Peninsula broadly known as Al-Andalus...

 of Ferdinand and Isabella. It was subsequently applied in the new cities established during the Spanish colonization of the Americas
Spanish colonization of the Americas
Colonial expansion under the Spanish Empire was initiated by the Spanish conquistadores and developed by the Monarchy of Spain through its administrators and missionaries. The motivations for colonial expansion were trade and the spread of the Christian faith through indigenous conversions...

, after the founding of San Cristóbal de La Laguna
San Cristóbal de la Laguna
San Cristóbal de La Laguna is a city and municipality in the northern part of the island of Tenerife in the Province of Santa Cruz de Tenerife, on the Canary Islands . The city is third-most populous city of the archipelago and second-most populous city of the island. It is a suburban area of the...

 (Canary Islands) in 1496. In 1573, King Phillip II of Spain compiled the Laws of the Indies to guide the construction and administration of colonial communities. The Laws specified a square or rectangular central plaza with eight principal streets running from the plaza's corners. Hundreds of grid-plan communities throughout the Americas were established according to this pattern, echoing the practices of earlier Indian civilizations.

The grid plan became popular with the start of the Renaissance
Renaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...

 in Northern Europe. In 1606, the newly founded city of Mannheim
Mannheim
Mannheim is a city in southwestern Germany. With about 315,000 inhabitants, Mannheim is the second-largest city in the Bundesland of Baden-Württemberg, following the capital city of Stuttgart....

 in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 was the first Renaissance city laid out on the grid plan. Later came the New Town in Edinburgh
Edinburgh
Edinburgh is the capital city of Scotland, the second largest city in Scotland, and the eighth most populous in the United Kingdom. The City of Edinburgh Council governs one of Scotland's 32 local government council areas. The council area includes urban Edinburgh and a rural area...

 and almost the entire city centre of Glasgow
Glasgow
Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...

, and many planned communities and cities in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 such as New Haven
New Haven, Connecticut
New Haven is the second-largest city in Connecticut and the sixth-largest in New England. According to the 2010 Census, New Haven's population increased by 5.0% between 2000 and 2010, a rate higher than that of the State of Connecticut, and higher than that of the state's five largest cities, and...

 and Adelaide
Adelaide
Adelaide is the capital city of South Australia and the fifth-largest city in Australia. Adelaide has an estimated population of more than 1.2 million...

.

The baroque
Baroque
The Baroque is a period and the style that used exaggerated motion and clear, easily interpreted detail to produce drama, tension, exuberance, and grandeur in sculpture, painting, literature, dance, and music...

 capital city of Malta
Malta
Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...

, Valletta
Valletta
Valletta is the capital of Malta, colloquially known as Il-Belt in Maltese. It is located in the central-eastern portion of the island of Malta, and the historical city has a population of 6,098. The name "Valletta" is traditionally reserved for the historic walled citadel that serves as Malta's...

, dating back to the 16th Century, was built following a rigid grid plan of uniformly designed houses, dotted with palaces, churches and squares.

Early United States

Many of the earliest cities in the United States, such as Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...

, did not start with a grid system. However, even in the pre-revolutionary days some cities saw the benefits of such a layout. New Haven Colony
New Haven Colony
The New Haven Colony was an English colonial venture in present-day Connecticut in North America from 1637 to 1662.- Quinnipiac Colony :A Puritan minister named John Davenport led his flock from exile in the Netherlands back to England and finally to America in the spring of 1637...

, one of the earliest colonies in America, was designed with a tiny 9-square grid at its founding in 1638. On a grander scale, Philadelphia was designed on a rectilinear street grid in 1682; one of the first cities in North America to use a grid system. At the urging of city founder William Penn
William Penn
William Penn was an English real estate entrepreneur, philosopher, and founder of the Province of Pennsylvania, the English North American colony and the future Commonwealth of Pennsylvania. He was an early champion of democracy and religious freedom, notable for his good relations and successful...

, surveyor Thomas Holme
Thomas Holme
Thomas Holme was the first Surveyor General of Pennsylvania to actually serve, in which capacity he laid out the original plan for the city of Philadelphia.-Life:...

 designed a system of wide streets intersecting at right angles between the Schuylkill River
Schuylkill River
The Schuylkill River is a river in Pennsylvania. It is a designated Pennsylvania Scenic River.The river is about long. Its watershed of about lies entirely within the state of Pennsylvania. The source of its eastern branch is in the Appalachian Mountains at Tuscarora Springs, near Tamaqua in...

 to the west and Delaware River
Delaware River
The Delaware River is a major river on the Atlantic coast of the United States.A Dutch expedition led by Henry Hudson in 1609 first mapped the river. The river was christened the South River in the New Netherland colony that followed, in contrast to the North River, as the Hudson River was then...

 to the east, including five squares of dedicated parkland. Penn advertised this orderly design as a safeguard against overcrowding, fire, and disease, which plagued European cities. Holme drafted an ideal version of the grid, but alleyways sprouted within and between larger blocks as the city took shape.
Arguably the most famous grid plan in history is the plan for New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 formulated in the Commissioners' Plan of 1811
Commissioners' Plan of 1811
The Commissioners' Plan of 1811 was the original design plan for the streets of Manhattan, which put in place the grid plan that has defined Manhattan to this day....

, a visionary proposal by the state legislature
Legislature
A legislature is a kind of deliberative assembly with the power to pass, amend, and repeal laws. The law created by a legislature is called legislation or statutory law. In addition to enacting laws, legislatures usually have exclusive authority to raise or lower taxes and adopt the budget and...

 of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 for the development of most of Manhattan
Manhattan
Manhattan is the oldest and the most densely populated of the five boroughs of New York City. Located primarily on the island of Manhattan at the mouth of the Hudson River, the boundaries of the borough are identical to those of New York County, an original county of the state of New York...

 above Houston Street.
Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

, the capital of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, was planned under French-American architect Pierre Charles L'Enfant
Pierre Charles L'Enfant
Pierre Charles L'Enfant was a French-born American architect and civil engineer best known for designing the layout of the streets of Washington, D.C..-Early life:...

. Under the L'enfant plan, the original District of Columbia was developed using a grid plan that is overlapped by diagonal avenues, most famously Pennsylvania Avenue
Pennsylvania Avenue
Pennsylvania Avenue is a street in Washington, D.C. that joins the White House and the United States Capitol. Called "America's Main Street", it is the location of official parades and processions, as well as protest marches...

. These diagonals are often connected by traffic circles, such as Dupont Circle
Dupont Circle
Dupont Circle is a traffic circle, park, neighborhood, and historic district in Northwest Washington, D.C. The traffic circle is located at the intersection of Massachusetts Avenue NW, Connecticut Avenue NW, New Hampshire Avenue NW, P Street NW, and 19th Street NW...

 and Washington Circle
Washington Circle
Washington Circle is a traffic circle in the Northwest quadrant of Washington, D.C., United States. It is the intersection of 23rd Street, K Street, New Hampshire Avenue, and Pennsylvania Avenue, N.W., on the border of the Foggy Bottom and West End neighborhoods. The through lanes of K Street...

. As the city began to grow in size, the plan was duplicated to cover most of the remainder of the capital. Meanwhile, the core of the city faced disarray and the McMillan Plan
McMillan Plan
The McMillan Plan was an architectural plan for the development of Washington, D.C., formulated in 1902 by the Senate Park Improvement Commission of the District of Columbia which had been formed by Congress the previous year.-United States Park Commission:...

, led by Senator James McMillan
James McMillan
James McMillan may refer to:* James McMillan , founder of Fort Langley, British Columbia* James W. McMillan , Union officer during the American Civil War* James McMillan , U.S. Senator from Michigan...

 was founded to build a National Mall
National Mall
The National Mall is an open-area national park in downtown Washington, D.C., the capital of the United States. The National Mall is a unit of the National Park Service , and is administered by the National Mall and Memorial Parks unit...

 and parks system, that is still today a jewel of the city.

Often, some of the streets in a grid are numbered (First, Second, etc.), lettered, or arranged in alphabetical order. (Washington, DC has examples of all three).

An exception to the typical, uniform grid is the plan of Savannah, GA (1733). It is a composite, cellular city block consisting of four large corner blocks, four small blocks in between and a public square in the centre. Its cellular structure includes all the primary land uses of a neighborhood and has for that reason been called fractal
Fractal
A fractal has been defined as "a rough or fragmented geometric shape that can be split into parts, each of which is a reduced-size copy of the whole," a property called self-similarity...

. Its street configuration presages contemporary traffic calming techniques applied to uniform grids where certain selected streets become discontinuous or narrow thus discouraging through traffic.

In the westward development of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, the use of the grid plan was nearly universal in the construction of new communities, such as in Salt Lake City (1870), Dodge City (1872) and Oklahoma City
Oklahoma city
Oklahoma City is the capital and largest city of the U.S. state of Oklahoma.Oklahoma City may also refer to:*Oklahoma City metropolitan area*Downtown Oklahoma City*Uptown Oklahoma City*Oklahoma City bombing*Oklahoma City National Memorial...

 (1890). In these western cities the streets were numbered even more carefully than in the east to suggest future prosperity and metropolitan status.

One of the main advantages of the adoption of the grid plan was that it allowed the rapid subdivision
Subdivision (land)
Subdivision is the act of dividing land into pieces that are easier to sell or otherwise develop, usually via a plat. The former single piece as a whole is then known in the United States as a subdivision...

 and auction
Auction
An auction is a process of buying and selling goods or services by offering them up for bid, taking bids, and then selling the item to the highest bidder...

 of a large parcel of land. For example, when the legislature of the Republic of Texas
Republic of Texas
The Republic of Texas was an independent nation in North America, bordering the United States and Mexico, that existed from 1836 to 1846.Formed as a break-away republic from Mexico by the Texas Revolution, the state claimed borders that encompassed an area that included all of the present U.S...

 decided in 1839 to move the capital to the new site along the Colorado River
Colorado River (Texas)
The Colorado River is a river that runs through the U.S. state of Texas; it should not be confused with the much longer Colorado River which flows from Colorado into the Gulf of California....

, the functioning of the government required the rapid population of the town, which was named Austin
Austin, Texas
Austin is the capital city of the U.S. state of :Texas and the seat of Travis County. Located in Central Texas on the eastern edge of the American Southwest, it is the fourth-largest city in Texas and the 14th most populous city in the United States. It was the third-fastest-growing large city in...

. Charged with the task, Edwin Waller
Edwin Waller
Judge Edwin Waller was an entrepreneur, signer of the Texas Declaration of Independence, the first mayor of Austin, Texas, and the designer of its downtown grid plan....

 designed a fourteen block grid that fronted the river on 640 acres (exactly 1 square mile; about 2.6 km²). After surveying the land, Waller organized the sale of 306 lots nearly immediately, and by the end of the year the entire Texas government had arrived by oxcart
Cart
A cart is a vehicle designed for transport, using two wheels and normally pulled by one or a pair of draught animals. A handcart is pulled or pushed by one or more people...

 at the new site. Apart from the speed of surveying advantage, the rationale at the time of the grid's adoption in this and other cities remains obscure.

Late 19th century to the present

Ildefons Cerdà
Ildefons Cerdà
Ildefons Cerdà i Sunyer was the progressive Catalan Spanish urban planner who designed the 19th-century "extension" of Barcelona called the Eixample.-Biography:...

 defined a concept of urban planning, based on the grid, that he applied to the Barcelona
Barcelona
Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...

 Eixample
Eixample
The Eixample is a district of Barcelona between the old city and what were once surrounding small towns , constructed in the 19th and early 20th centuries....

. The Eixample grid introduced innovative design elements that made it exceptional at the time and even unique among subsequent grid plans: a) a very large block measuring 113m by 113m (370 x 370 feet) far larger than the old city blocks and larger than any Roman, Greek blocks and their mutations (see drawing below); b) a 20 m (66 feet) road width (right of way) compared to mostly 3 m in the old city c) square blocks with truncated corners and d) major roads perpendicular and diagonal measuring 50 m (164 feet) in width. These innovations he based on functional grounds: the block size, to enable the creation of a quiet interior open space(60 m by 60 m) and allow ample sunlight and ventilation to its perimeter buildings; the rectilinear geometry, the wide streets and boulevards to sustain high mobility and the truncated corners to facilitate turning of carts and coaches and particularly vehicles on fixed rails.

In maps of larger American cities, mostly east of the Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

, it can be noted that the downtown areas are almost always grids. These areas represent the original land dimensions of the founded city, generally one square mile. Some cities expanded the grid further out from the centre but maps also show that, in general, as the distance from the centre increases a variety of patterns emerge in no particular discernible order . In juxtaposition to the grid they appear random. These new patterns have been systematically classified and their design characteristics measured

In the United States, the grid system was widely used in most major cities and their suburb
Suburb
The word suburb mostly refers to a residential area, either existing as part of a city or as a separate residential community within commuting distance of a city . Some suburbs have a degree of administrative autonomy, and most have lower population density than inner city neighborhoods...

s until the 1960s. However, during the 1920s, the rapid adoption of the automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 caused a panic among urban planners
Urban planning
Urban planning incorporates areas such as economics, design, ecology, sociology, geography, law, political science, and statistics to guide and ensure the orderly development of settlements and communities....

, who, based on observation, claimed that speeding cars would eventually kill tens of thousands of small children per year. Apparently, at this early stage of the car’s entry into the grid, the streets of major cities worldwide were the scene of virtual “slaughter” as the fatality rate per 100,000 pop was more than double the current. In 2009, after several decades of road safety improvements and a constant decline in fatalities, an estimated 33,963 people died in motor vehicle traffic crashes and, according to the National Highway Traffic Safety Administration, “Motor vehicle crashes are the leading cause of death for children from 3 to 14 years old.”. Planners, therefore, called for an inwardly focused "superblock" arrangement that minimized through automobile traffic and discouraged it from traveling on anything but arterial road
Arterial road
An arterial road, or arterial thoroughfare, is a high-capacity urban road. The primary function of an arterial road is to deliver traffic from collector roads to freeways, and between urban centres at the highest level of service possible. As such, many arteries are limited-access roads, or feature...

s; traffic generators, such as apartment complexes and shops, would be restricted to the edges of the superblock, along the arterial. This paradigm prevailed between approximately 1930 and 1960, especially in Los Angeles
Los Angeles, California
Los Angeles , with a population at the 2010 United States Census of 3,792,621, is the most populous city in California, USA and the second most populous in the United States, after New York City. It has an area of , and is located in Southern California...

, where notable examples include Leimert Park
Leimert Park, Los Angeles, California
Leimert Park is a neighborhood in Los Angeles, California roughly bounded by Rodeo Road on the north, 4th Avenue and Roxton Avenue on the east, Vernon Avenue on the south, and Crenshaw Boulevard on the west. Crenshaw District lies to the south, View Park to the west, Vermont Square to the east,...

 (an early example) and Panorama City
Panorama City, Los Angeles, California
Panorama City is a district in the San Fernando Valley region of the city of Los Angeles, California. It is known as the San Fernando Valley's first planned community.-Description:...

 (a late-period one).

A prominent 20th century urbanist, Lewis Mumford
Lewis Mumford
Lewis Mumford was an American historian, philosopher of technology, and influential literary critic. Particularly noted for his study of cities and urban architecture, he had a broad career as a writer...

, severely criticized some of the grid's characteristics: “With a T-square and a triangle, finally, the municipal engineer could, without the slightest training as either an architect or a sociologist, ‘plan’ a metropolis, with its standard lots, its standard blocks, its standard street widths, in short, with its standardized comparable, and replaceable parts. The new gridiron plans were spectacular in their inefilciency and waste. By usually failing to discriminate sufficiently between main arteries and residential streets, the first were not made wide enough while the second were usually too wide for purely neighborhood functions . . . as for its contribution to the permanent social functions of the city, the anonymous
gridiron plan proved empty.”

In the 1960s, traffic engineer
Traffic engineering
Traffic engineering can mean:* traffic engineering , a branch of civil engineering* teletraffic engineering, a field of statistical techniques used in telecommunications...

s and urban planners abandoned the grid virtually wholesale in favor of a "street hierarchy
Street hierarchy
The street hierarchy is an urban design technique for laying out road networks that exclude automobile through-traffic from developed areas. It is conceived as a hierarchy of roads that embeds the link importance of each road type in the network topology...

". This is a thoroughly "asymmetric" street arrangement in which a residential subdivision—often surrounded by a noise wall
Noise barrier
A noise barrier is an exterior structure designed to protect sensitive land uses from noise pollution...

 or a security gate
Gated community
In its modern form, a gated community is a form of residential community or housing estate containing strictly-controlled entrances for pedestrians, bicycles, and automobiles, and often characterized by a closed perimeter of walls and fences. Gated communities usually consist of small residential...

—is completely separated from the road network except for one or two connections to arterial roads. In a way, this is a return to medieval styles: as noted in Spiro Kostof
Spiro Kostof
Dr. Spiro Konstantine Kostof was a leading architectural historian and inspirational teacher at the University of California, Berkeley. His books continue to be widely read and some are routinely used in collegiate courses on architectural history.A Bulgarian born in Turkey, Kostof was educated...

's seminal history of urban design
Urban design
Urban design concerns the arrangement, appearance and functionality of towns and cities, and in particular the shaping and uses of urban public space. It has traditionally been regarded as a disciplinary subset of urban planning, landscape architecture, or architecture and in more recent times has...

, The City Shaped, there is a strong resemblance between the street arrangements of modern American suburbs and those of medieval Arab
Arab
Arab people, also known as Arabs , are a panethnicity primarily living in the Arab world, which is located in Western Asia and North Africa. They are identified as such on one or more of genealogical, linguistic, or cultural grounds, with tribal affiliations, and intra-tribal relationships playing...

 and Moorish cities. In each case, the community unit at hand—the clan or extended family in the Muslim
Muslim
A Muslim, also spelled Moslem, is an adherent of Islam, a monotheistic, Abrahamic religion based on the Quran, which Muslims consider the verbatim word of God as revealed to prophet Muhammad. "Muslim" is the Arabic term for "submitter" .Muslims believe that God is one and incomparable...

 world, the economically homogeneous subdivision
Subdivision (land)
Subdivision is the act of dividing land into pieces that are easier to sell or otherwise develop, usually via a plat. The former single piece as a whole is then known in the United States as a subdivision...

 in modern suburbia—isolates itself from the larger urban scene by using dead ends and culs-de-sac
Cul-de-sac
A cul-de-sac is a word of French origin referring to a dead end, close, no through road or court meaning dead-end street with only one inlet/outlet...

.

Milton Keynes

One very famous use of the grid system was in the British new town of Milton Keynes
Milton Keynes
Milton Keynes , sometimes abbreviated MK, is a large town in Buckinghamshire, in the south east of England, about north-west of London. It is the administrative centre of the Borough of Milton Keynes...

. In this planned city, which began construction in 1967, a system of ten horizontal and eleven vertical roads at 1 km intervals was used with roundabout
Roundabout
A roundabout is the name for a road junction in which traffic moves in one direction around a central island. The word dates from the early 20th century. Roundabouts are common in many countries around the world...

s at each intersection. The horizontal roads were all given names ending in 'way' and H numbers (for 'horizontal', 'e.g. H3 Monks Way). The vertical roads were given names ending in 'street' and V numbers (for vertical', e.g. V6 Grafton Street
V6 Grafton Street
The V6 Grafton Street is a major local road in Milton Keynes. Its formal name is simply "Grafton Street": the "V6" designation is an urban planning name that indicates that it is the sixth north-south grid road in the Milton Keynes grid road system....

). Each grid road was spaced roughly one kilometre along from the next, forming squares of approximately one square kilometre. Each square and roundabout was given its own name. The system provided very easy transport within the city, although it confused visitors who were unfamiliar with the system. Note the 'grid squares thus formed are far larger than the city blocks described earlier, and the road layouts within the grid squares are generally 'organic' in form — matching the 'street hierarchy model described above

Financial cost

The infrastructure cost for regular grid patterns is generally higher than for patterns with discontinuous streets. Costs for streets depend largely on four variables: street width (or Right of Way (ROW); street length, block width and pavement width.

Street width (ROW) influences the amount of land that is devoted to streets, which becomes unavailable for development and therefore represents an opportunity cost. The wider the street the higher the opportunity cost. Street width is determined by circulation and aesthetic considerations and is not dependent on the pattern configuration. Any configuration can have wide or narrow streets.

Street length influences proportionately the amount of street components that have to be constructed such as pavement, curbs and sidewalks, storm sewers and drains, light poles, and trees. The street length of a given area of development depends on the frequency at which streets occur which in turn depends on the length and width of a block. The higher the frequency of streets the longer is their total length. The smaller the block dimensions the higher the frequency of the streets. As the frequency of street increases so does the number of intersections. Intersections normally cost more than straight street length because they are labour intensive and require street and traffic signage.

Pavement width influences the cost by affecting the amount of materials and labour required to provide a finished road surface. Pavement width is generally based on traffic engineering considerations and is not dependent on pattern configuration. As with the street width, any pattern can have wide or narrow pavements.
Of all three factors that affect cost, street width, street length and pavement width, only street length is pattern dependent. An objective cost comparison would, therefore, rely on this variable with the full understanding that the other variables, though optional, can play a role.

Traditional orthogonal grid patterns generally have greater street frequencies than discontinuous patterns. For example, Portland's block is 200 feet X 200 feet while Miletus' is half that size and Timgad's half again (see diagram). Houston, Sacramento and Barcelona are progressively bigger reaching up to four times the area of Portland's block. New York's 1811 plan (see above) has blocks of 200 ft. in width and variable lengths ranging from about 500 to 900 feet. The corresponding frequency of streets for each of these block sizes affects the street length.

A simple example of a grid street pattern (see diagram) illustrates the progressive reduction in total street length and the corresponding increase in block length. For a corresponding reduction of one, two, three and four streets within this 40 acres (16.2 ha) parcel, the street length is reduced from an original total of 12,600 to 7,680 linear feet, a 39% reduction.
Simultaneously, block lengths increase from 200 X 200 feet to 1240 X 200 feet. When all five blocks have reached the ultimate size of 1240 feet, four street lengths out of total eight have been eliminated. Block lengths of 1000 foot or larger rarely appear in grid plans and are not recommended as they hinder pedestrian movement (Pedestrianism, below). From the pedestrian perspective, the smaller the block is, the easier the navigation and the more direct the route. Consequently, the finer grids are preferred.

Patterns that incorporate discontinuous street types such as crescents and cul-de-sacs have not, in general, regarded pedestrian movement as a priority and, consequently, have produced blocks that are usually in the 1000-foot range and often exceed it. As a result, street frequency drops and so does the total street length and, therefore, the cost. In general, it is not the street pattern per se that affects costs but the frequency of streets that it either necessitates or purposely incorporates.

An inherent advantage of the orthogonal geometry of a proper grid is its tendency to yield regular lots in well-packed sequences. This maximizes the use of the land of the block; it does not, however, affect street frequency. Any frequency of orthogonal streets produces the same packing
Packing
Packing may refer to:In Mechanical engineering:* Packing, also known as an O-ring or other type of Seal , a term for a sealing materialIn Chemical engineering:* Structured packing, i.e...

 effect. Orthogonal geometry also minimizes disputes over lot boundaries and maximized the number of lots that could front a given street. John Randal said Manhattan's grid plan facilitated "buying, selling and improving real estate"/

Ecological features, rain water absorption and pollutant generation

Typical, uniform grids are unresponsive to topography. Priene
Priene
Priene was an ancient Greek city of Ionia at the base of an escarpment of Mycale, about north of the then course of the Maeander River, from today's Aydin, from today's Söke and from ancient Miletus...

’s plan, for example, is set on a hill side and most of its north-south streets are stepped, a feature that would have made them inaccessible to carts, chariots and loaded animals. Other contemporary cities followed Priene’s example e.g. San Francisco, Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...

, and Saint John, New Brunswick
Saint John, New Brunswick
City of Saint John , or commonly Saint John, is the largest city in the province of New Brunswick, and the first incorporated city in Canada. The city is situated along the north shore of the Bay of Fundy at the mouth of the Saint John River. In 2006 the city proper had a population of 74,043...

. In a contemporary context, steep grades limit accessibility by car, and more so by bicycle, on foot, or wheelchair, particularly in cold climates.

The same inflexibility of the grid leads to disregarding environmentally sensitive areas such as small streams and creeks or mature woodlots in preference for the application of the immutable geometry. It is said of the NY grid plan that it flattened all obstacles in its way. By contrast, recent discontinuous street patterns follow the configuration of natural features without disrupting them. The grid represents a rationalist, reductionist solution to a multifaceted issue.

The grid’s inherent high street and intersection frequencies produce large areas of impermeable surfaces in the street pavement and the sidewalks. In comparison to recent networks with discontinuous street types, grids can be up to 30% percent higher in impermeable surfaces attributable to roads. The emerging environmental priority of retaining as much as 90% of rain water on site becomes problematic with high percentages of impermeable surfaces. And since roads constitute the largest share of the total impermeable surfaces of a development, the difficulty is compounded by the grid type of layout. For these reasons contemporary planners have attempted to modify the rigid, uniform, classic grid.

Some cities, notably Seattle, have devised means to improve a street’s retention capacity. However, frequent intersections as they occur in a regular grid would pose an obstacle to their effective application.

A street network pattern can affect the production of pollutants by the amount of car travel that it necessitates and the speed at which cars can travel. The grid plan with its frequent intersections may displace a portion of the local car trips with walking or biking due to the directness of route that it offers to pedestrians. But it also makes the same routes more direct for cars, which could be an enticement for driving. The potential car trip displacement would result in a reduction of pollutant emissions. The advantage of the intersection density for pedestrians, however, can have a contrary effect for cars due to its potential for reducing speeds. Low speeds below 20 mph have a significantly higher coefficient of pollutant production than above 30, though the coefficient after levelling off tends to increase gradually after 50 mph. This effect is accentuated with high traffic density in areas with commercial uses where speeds come to a crawl. Since the grid plan is non-hierarchical and intersections are frequent, all streets can be subject to this potential reduction of average speeds, leading to a high production of pollutants. Greenhouse and noxious gases can be detrimental to the environment and to resident health.

Social environment and security

In his seminal study (1982) on livable streets
Livable Streets
Livable Streets is a 1981 book by Donald Appleyard in which he shows that streets have many social and recreational functions that may be severely impaired by high-speed car traffic....

, that was conducted in neighbourhoods with a grid, Donald Appleyard showed that social networking and street playing degraded as traffic increased on a street. His research provided the groundwork for traffic calming
Traffic calming
Traffic calming is intended to slow or reduce motor-vehicle traffic in order to improve the living conditions for residents as well as to improve safety for pedestrians and cyclists. Urban planners and traffic engineers have many strategies for traffic calming...

 and for several initiatives such as living street
Living street
A living street is a street in which, unlike in most 20th century streets, the needs of car drivers are secondary to the needs of users of the street as a whole. It is a space designed to be shared by pedestrians, playing children, bicyclists, and low-speed motor vehicles...

s and Home Zone
Home zone
Home Zone is a term used in the United Kingdom for a residential street or group of streets that are designed primarily to meet the interests of the local community, whether they are on foot, cycling, or in a car, enabling the street to operate primarily as a space for social use...

s, all of which are aimed at improving a street’s social milieu.

The amount of traffic on a street depends on variables such as the population density of the neighbourhood, car ownership and its proximity to commercial, institutional or recreational edifices. Most importantly, however, it depends on whether a street is or could become a through road to a destination. As a through road, it could sustain unpredictable levels of traffic that may fluctuate during the day and increase over time. A key characteristic of the grid pattern is that any and all streets are equally accessible to traffic (non-hierarchical) and could be chosen at will as alternative routes to a destination. Cut-through driving, or shortcutting, has been resisted by residents. Cities responded by making modifications to prevent it. Current recommended design practice suggests the use of 3-way intersections to alleviate it. The geometry of the normal, open grid is evidently unsuitable for protecting or enhancing the social environment of a street from the negative influence of traffic.

Similarly, a 1972 ground-breaking study by Oscar Newman on a Defensible Space Theory
Defensible Space Theory
The defensible space theory of architect and city planner Oscar Newman encompasses ideas about crime prevention and neighborhood safety. The theory developed in the early 1970s, and he wrote his first book on the topic, Defensible Space in 1972...

 described ways to improve the social environment and security of neighbourhoods and streets. In a practical application of his theory at Five Oaks, the neighbourhood's grid pattern was modified to prevent through traffic and create identifiable smaller enclaves while maintaining complete pedestrian freedom of movement. The positive outcome of these changes reinforces Appleyard's findings and the need to reduce or prevent through traffic on neighbourhood streets; a need that cannot be met with a typical, uniform, open grid.

The question of neighbourhood security has been a constant focus of research since Oscar Newman's work. New research has expanded the discussion on this disputed issue. A recent study did extensive spatial analysis and correlated several building, site plan and social factors with crime frequencies and identified subtle nuances to the contrasting positions. The study looked at, among others, dwelling types, unit density (site density) movement on the street, culs–de-sac or grids and the permeability of a residential area.

Among its conclusions are, respectively, that flats are always safer than houses and the wealth of inhabitants matters, density is generally beneficial but more so at ground level, local movement is beneficial, but not larger scale movement, relative affluence and the number of neighbours have a greater effect than either being on a cul-de-sac or being on a through street. It also re-established that simple, linear culs-de-sac with good numbers of dwellings that are joined to through streets tend to be safe. As for permeability, it suggests that residential areas should be permeable enough to allow movement in all directions but no more. The overprovision of poorly used permeability is a crime hazard. The open, uniform grid could be seen as an example of undifferentiated permeabilty.

A recent study in California examined the amount of child play that occurred on the streets of neighbourhoods with different characteristics; grid pattern and cul-de-sacs. The findings indicate that the open grid streets showed substantially lower play activity than the cul-de-sac street type. Cul-de-sacs reduce perceived danger from traffic thereby encouraging more outdoor play. It pointed the way toward the development of hybrid street network patterns that improve pedestrian movement but restrict cut-through driving.

Similar studies in Europe and most recently in Australia found that children's outdoor play is significantly reduced on through roads where traffic is, or perceived by parents to be, a risk.

Traditional street functions such a kids play, strolling and socializing are incompatible with traffic flow, which the open, uniform grid geometry encourages. For these reasons, cities such as Berkeley, CA and Vancouver, BC, among many others, transformed existing residential streets part of a grid plan into permeable, linked culs-de-sac. This transformation retains the permeability
Permeability (spatial and transport planning)
Permeability or connectivity describes the extent to which urban forms permit movement of people or vehicles in different directions. The terms are often used interchangeably, although differentiated definitions also exist...

 and connectivity of the grid for the active modes of transport but filters and restricts car traffic on the cul-de-sac street to residents only.

Pedestrian and bicycle movement

Two inherent characteristics of the grid plan, frequent intersections and orthogonal geometry, assist pedestrian
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

 movement. The geometry helps with orientation and wayfinding
Wayfinding
Wayfinding encompasses all of the ways in which people and animals orient themselves in physical space and navigate from place to place.-Historical:...

 and its frequent intersections with the choice and directness of route to desired destinations. Street networks of old cities that grew organically, though admired for being picturesque, can be confusing for visitors but rarely for the original inhabitants (see plan). Similarly confusing to visitors are the plans of contemporary subdivisions with discontinuous and curvilinear streets. Change of street orientation, particularly when gradual or arbitrary, cannot be “mapped” in the mind. Impasses, crescents or cul-de-sacs frustrate the traveler especially when they are long, forcing an arduous retracing of steps.

Frequency of intersections, however, becomes also a disadvantage for pedestrians and bicycles. It disrupts the relaxed canter of walking and forces pedestrians repeatedly onto the road, a hostile, anxiety-generating territory. People with physical limitations or frailties, children and seniors for example, can find such walk challenging. For bicycles this disadvantage is accentuated as their normal speed is at least double that of pedestrians. Frequent stops negate the speed advantage and the physical benefit of bicycling and add to frustration. Intersections are not only unpleasant but also dangerous. Most traffic collisions and injuries occur at intersections and the majority of the injuries to pedestrians crossing with the right of way.

A dilemma arises from trying to meet important planning objectives when using the grid: pedestrianism, cost efficiency and environmental responsiveness. To serve pedestrians well, a rectangular configuration and high frequency of streets and intersections is the preferred route, which the orthogonal grid geometry provides. To reduce development costs and environmental impact, lower frequency of streets is the logical path. Since these two design objectives are contradictory a balance needs to be struck. Such balance has been achieved in leading contemporary projects such as Vauban, Freiburg
Vauban, Freiburg
Vauban is a new neighborhood of 5,000 inhabitants and 600 jobs 4 km to the south of the town center in Freiburg, Germany. It was built as "a sustainable model district" on the site of a former French military base, and is named after Sébastien Le Prestre de Vauban, the 17th century French...

 and Village Homes
Village Homes
Village Homes is a planned community in Davis, California, designed to be ecologically sustainable. The more than 200 houses in the development utilize solar panels for heating, and are oriented around common areas at the rear of the buildings, rather than around the street at the front...

, Davis. Both score high in pedestrian and bike mode share and, at the same time, in reducing negative development externalities. Their layout configurations represent a fusion of the classic grid plan with recent street network patterns.

Examining the issue of walkability, a recent comparison of seven neighbourhood layouts found a 43 and 32 percent increase in walking with respect to a grid plan and conventional suburban layout in a Fused Grid
Fused Grid
The Fused Grid is a street network pattern first proposed in 2002 and subsequently applied in Calgary, Alberta and in Stratford, Ontario . It represents a synthesis of two well known and extensively used network concepts: the "grid" and the “Radburn” pattern, derivatives of which are found in most...

 layout, which has greater permeability for pedestrians than for cars due to its inclusion of dedicated pedestrian paths. It also showed a 7 to 10 percent range of reduction in driving with respect to the remainder six neighbourhood layouts in the set, an environmental benefit.

Safety

Perceived and actual safety play a role in the use of the street. Perceived safety, though may be an inaccurate reflection of the number injuries or fatalities, influences parents’ decision to allow their children to play, walk or bike on the street. Actual levels of safety as measured by the total number of collisions and the number and severity of injuries are a matter of public concern. Both should inform the layout, if the street network is to achieve its optimum use.

Recent studies have found higher traffic fatality rates in outlying suburban areas than in central cities and inner suburbs with smaller blocks and more-connected street patterns. While some of this disparity is the result of distance from emergency medical
Emergency medical services
Emergency medical services are a type of emergency service dedicated to providing out-of-hospital acute medical care and/or transport to definitive care, to patients with illnesses and injuries which the patient, or the medical practitioner, believes constitutes a medical emergency...

 facilities (hospitals are usually built in a fairly late stage of the development of a suburban area), it is clear that the lower speeds encouraged by the frequency of intersections decrease the severity of accidents occurring on streets within a grid plan.

An earlier study found significant differences in recorded accidents between residential neighbourhoods that were laid out on a grid and those that included cul-de-sacs and crescents. The frequency of accidents was significantly higher in the grid neighbourhoods.

Two newer studies examined the frequency of collisions in two regional districts using the latest analytical tools. They investigated the potential correlation between street network patterns and frequency of collisions. In one study, cul-de-sac networks appeared to be much safer than grid networks, by nearly three to one.
A second study found the grid plan to be the least safe by a significant margin with respect to all other street patterns.

A 2009 study suggests that land use patterns play a significant role in traffic safety and should be considered in conjunction with the network pattern. While all intersection types in general reduce the incidence of fatal crashes, four-way intersections, which occur regularly in a grid, increase total and injurious crashes significantly. The study recommends hybrid street networks with dense concentrations of T-intersections and concludes that a return to the 19th century gridiron is undesirable.

Stringent adherence to the grid plan can cause steep inclines since the topology of the land is not taken into account. This may be unsafe for drivers, pedestrians and bicycles since it is more difficult to control speed and braking, particularly in winter conditions.

Reconstruction and development

One of the greatest difficulties with grid plans is their lack of specialisation, most of the important amenities being concentrated along the city's main arteries. Often grid plans are found in linear settlements
Ribbon development
Ribbon development means building houses along the routes of communications radiating from a human settlement. Such development generated great concern in the United Kingdom during the 1920s and the 1930s, as well as in numerous other countries....

, with a main street connecting between the perpendicular roads. However, this can be mitigated by allowing mixed use development so that destinations become closer to home. Many cities, especially in Latin America, still successfully retain their grid plans. Recently, planners in the United States and Canada have revisited the idea of reintroducing grid patterns to many cities and towns.

See also

  • City block
    City block
    A city block, urban block or simply block is a central element of urban planning and urban design. A city block is the smallest area that is surrounded by streets. City blocks are the space for buildings within the street pattern of a city, they form the basic unit of a city's urban fabric...

  • United States
    United States
    The United States of America is a federal constitutional republic comprising fifty states and a federal district...

     - Land Ordinance of 1785
    Land Ordinance of 1785
    The Land Ordinance of 1785 was adopted by the United States Congress on May 20, 1785. Under the Articles of Confederation, Congress did not have the power to raise revenue by direct taxation of the inhabitants of the United States...

  • Urban structure
    Urban structure
    Urban structure is the arrangement of land use in urban areas. Sociologists, economists, and geographers have developed several models, explaining where different types of people and businesses tend to exist within the urban setting. Three models are described in this article...

  • Urban planning
    Urban planning
    Urban planning incorporates areas such as economics, design, ecology, sociology, geography, law, political science, and statistics to guide and ensure the orderly development of settlements and communities....

  • Street hierarchy
    Street hierarchy
    The street hierarchy is an urban design technique for laying out road networks that exclude automobile through-traffic from developed areas. It is conceived as a hierarchy of roads that embeds the link importance of each road type in the network topology...

  • Fused Grid
    Fused Grid
    The Fused Grid is a street network pattern first proposed in 2002 and subsequently applied in Calgary, Alberta and in Stratford, Ontario . It represents a synthesis of two well known and extensively used network concepts: the "grid" and the “Radburn” pattern, derivatives of which are found in most...

  • Permeability (spatial and transport planning)
    Permeability (spatial and transport planning)
    Permeability or connectivity describes the extent to which urban forms permit movement of people or vehicles in different directions. The terms are often used interchangeably, although differentiated definitions also exist...

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