Access management
Encyclopedia
Access management, when used in traffic and traffic engineering
circles, generally refers to the regulation of interchanges, intersections, driveways and median openings to a roadway. Its objectives are to enable access to land uses while maintaining roadway safety and mobility through controlling access location, design, spacing and operation. This is particularly important for major roadways intended to provide efficient service to through-traffic movements.
Access management is most evident on freeways (UK term motorways) where access is grade separated and all movements are via dedicated ramps. It is very important on arterial roads where at-grade intersections and private driveways greatly increase the number of conflicts involving vehicles, cyclists, and pedestrians. It is also important on minor roadways for safety considerations such as driver sight distance.
Planners, engineers, architects, developers, elected officials
, citizens and attorneys all play a significant role in access management. Businesses frequently view any attempt to limit access to their land uses as economically detrimental. This can make implementation controversial. However there is evidence showing that access management can have the positive effect of increasing market area
through reducing travel times on major roadways, and that minor increases in circuity do not cause customers to stop patronizing businesses.
The most authoritative North American reference on the subject is the Access Management Manual produced in 2003 by the Transportation Research Board
of the National Academy of Sciences
.
Colorado was the first state to enact legislation in 1979 and to adopt an associated code of practice and regulatory framework. Since that time, transportation agency interest in access management has grown significantly.
1. Provide a Specialized Roadway System:
Different types of roadways serve different functions. It is important to design and manage roadways according to the primary functions that they are expected to serve.
2. Limit Direct Access to Major Roadways:
Roadways that serve higher volumes of regional through traffic need more access control to preserve their traffic function. Frequent and direct property access is more compatible with the function of local and collector roadways.
3. Promote Intersection Hierarchy:
An efficient transportation network provides appropriate transitions from one classification of roadway to another. For example, freeways connect to arterials through an interchange that is designed for the transition. Extending this concept to other roadways results in a series of intersection types that range from the junction of two major arterial roadways, to a residential driveway connecting to a local street.
4. Locate Signals to Favor Through Movements:
Long, uniform spacing of intersections and signals on major roadways enhances the ability to coordinate signals and to ensure continuous movement of traffic at the desired speed. Failure to carefully locate access connections or median openings that later become signalized, can cause substantial increases in arterial travel times. In addition, poor signal placement may lead to delays that cannot be overcome by computerized signal timing
systems.
5. Preserve the Functional Area of Intersections and Interchanges:
The functional area of an intersection or interchange is the area that is critical to its safe and efficient operation. This is the area where motorists are responding to the intersection or interchange, decelerating, and maneuvering into the appropriate lane to stop or complete a turn. Access connections too close to intersections or interchange ramps can cause serious traffic conflicts that result in crashes and congestion.
6. Limit the Number of Conflict Points:
Drivers make more mistakes and are more likely to have collisions when they are presented with the complex driving situations created by numerous conflict points. Conversely, simplifying the driving task contributes to improved traffic operations and fewer collisions. A less complex driving environment is accomplished by limiting the number and type of conflicts between vehicles, vehicles and pedestrians, and vehicles and bicyclists.
7. Separate Conflict Areas:
Drivers need sufficient time to address one set of potential conflicts before facing another. The necessary spacing between conflict areas increases as travel speed increases, to provide drivers adequate perception and reaction time. Separating conflict areas helps to simplify the driving task and contributes to improved traffic operations and safety.
8. Remove Turning Vehicles from Through Traffic Lanes:
Turning lanes allow drivers to decelerate gradually out of the through lane and wait in a protected area
for an opportunity to complete a turn. This reduces the severity and duration of conflict between turning vehicles and through traffic and improves the safety and efficiency of roadway intersections.
9. Use Nontraversable Medians to Manage Left-Turn Movements:
Medians channel turning movements on major roadways to controlled locations. Research has shown that the majority of access-related crashes involve left turns. Therefore, nontraversable medians and other techniques that minimize left turns or reduce the driver workload can be especially effective in improving roadway safety.
10. Provide a Supporting Street and Circulation System:
Well-planned communities provide a supporting network of local and collector streets to accommodate development, as well as unified property access and circulation systems. Interconnected street and circulation systems support alternative modes of transportation and provide alternative routes for bicyclists, pedestrians, and drivers. Alternatively, commercial strip
development with separate driveways for each business forces even short trips onto arterial roadways, thereby reducing safety and impeding mobility.
Traffic engineering
Traffic engineering can mean:* traffic engineering , a branch of civil engineering* teletraffic engineering, a field of statistical techniques used in telecommunications...
circles, generally refers to the regulation of interchanges, intersections, driveways and median openings to a roadway. Its objectives are to enable access to land uses while maintaining roadway safety and mobility through controlling access location, design, spacing and operation. This is particularly important for major roadways intended to provide efficient service to through-traffic movements.
Access management is most evident on freeways (UK term motorways) where access is grade separated and all movements are via dedicated ramps. It is very important on arterial roads where at-grade intersections and private driveways greatly increase the number of conflicts involving vehicles, cyclists, and pedestrians. It is also important on minor roadways for safety considerations such as driver sight distance.
Planners, engineers, architects, developers, elected officials
Official
An official is someone who holds an office in an organization or government and participates in the exercise of authority .A government official or functionary is an official who is involved in public...
, citizens and attorneys all play a significant role in access management. Businesses frequently view any attempt to limit access to their land uses as economically detrimental. This can make implementation controversial. However there is evidence showing that access management can have the positive effect of increasing market area
Market area
A market area is a geographic zone containing the people who are likely to purchase a firm's goods or services....
through reducing travel times on major roadways, and that minor increases in circuity do not cause customers to stop patronizing businesses.
The most authoritative North American reference on the subject is the Access Management Manual produced in 2003 by the Transportation Research Board
Transportation Research Board
The Transportation Research Board is a division of the National Research Council, which serves as an independent adviser to the President, the Congress and federal agencies on scientific and technical questions of national importance...
of the National Academy of Sciences
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...
.
Colorado was the first state to enact legislation in 1979 and to adopt an associated code of practice and regulatory framework. Since that time, transportation agency interest in access management has grown significantly.
Principles of Access Management
Access management programs seek to limit and consolidate access along major roadways, while promoting a supporting street system and unified access and circulation systems for development. The result is a roadway that functions safely and efficiently for its useful life, and a more attractive corridor. The goals of access management are accomplished by applying the following principles:1. Provide a Specialized Roadway System:
Different types of roadways serve different functions. It is important to design and manage roadways according to the primary functions that they are expected to serve.
2. Limit Direct Access to Major Roadways:
Roadways that serve higher volumes of regional through traffic need more access control to preserve their traffic function. Frequent and direct property access is more compatible with the function of local and collector roadways.
3. Promote Intersection Hierarchy:
An efficient transportation network provides appropriate transitions from one classification of roadway to another. For example, freeways connect to arterials through an interchange that is designed for the transition. Extending this concept to other roadways results in a series of intersection types that range from the junction of two major arterial roadways, to a residential driveway connecting to a local street.
4. Locate Signals to Favor Through Movements:
Long, uniform spacing of intersections and signals on major roadways enhances the ability to coordinate signals and to ensure continuous movement of traffic at the desired speed. Failure to carefully locate access connections or median openings that later become signalized, can cause substantial increases in arterial travel times. In addition, poor signal placement may lead to delays that cannot be overcome by computerized signal timing
Signal timing
Signal timing is the technique which traffic engineers use to determine who has the right-of-way at an intersection. Signal timing involves deciding how much green time the traffic lights shall provide at an intersection approach, how long the pedestrian WALK signal should be, and many numerous...
systems.
5. Preserve the Functional Area of Intersections and Interchanges:
The functional area of an intersection or interchange is the area that is critical to its safe and efficient operation. This is the area where motorists are responding to the intersection or interchange, decelerating, and maneuvering into the appropriate lane to stop or complete a turn. Access connections too close to intersections or interchange ramps can cause serious traffic conflicts that result in crashes and congestion.
6. Limit the Number of Conflict Points:
Drivers make more mistakes and are more likely to have collisions when they are presented with the complex driving situations created by numerous conflict points. Conversely, simplifying the driving task contributes to improved traffic operations and fewer collisions. A less complex driving environment is accomplished by limiting the number and type of conflicts between vehicles, vehicles and pedestrians, and vehicles and bicyclists.
7. Separate Conflict Areas:
Drivers need sufficient time to address one set of potential conflicts before facing another. The necessary spacing between conflict areas increases as travel speed increases, to provide drivers adequate perception and reaction time. Separating conflict areas helps to simplify the driving task and contributes to improved traffic operations and safety.
8. Remove Turning Vehicles from Through Traffic Lanes:
Turning lanes allow drivers to decelerate gradually out of the through lane and wait in a protected area
Protected area
Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...
for an opportunity to complete a turn. This reduces the severity and duration of conflict between turning vehicles and through traffic and improves the safety and efficiency of roadway intersections.
9. Use Nontraversable Medians to Manage Left-Turn Movements:
Medians channel turning movements on major roadways to controlled locations. Research has shown that the majority of access-related crashes involve left turns. Therefore, nontraversable medians and other techniques that minimize left turns or reduce the driver workload can be especially effective in improving roadway safety.
10. Provide a Supporting Street and Circulation System:
Well-planned communities provide a supporting network of local and collector streets to accommodate development, as well as unified property access and circulation systems. Interconnected street and circulation systems support alternative modes of transportation and provide alternative routes for bicyclists, pedestrians, and drivers. Alternatively, commercial strip
Commerce
While business refers to the value-creating activities of an organization for profit, commerce means the whole system of an economy that constitutes an environment for business. The system includes legal, economic, political, social, cultural, and technological systems that are in operation in any...
development with separate driveways for each business forces even short trips onto arterial roadways, thereby reducing safety and impeding mobility.