The A4042 is a trunk road

Trunk road

A trunk road, trunk highway, or strategic road is a major road—usually connecting two or more cities, ports, airports, and other things.—which is the recommended route for long-distance and freight traffic...

 that runs from Abergavenny

Abergavenny

Abergavenny , meaning Mouth of the River Gavenny, is a market town in Monmouthshire, Wales. It is located 15 miles west of Monmouth on the A40 and A465 roads, 6 miles from the English border. Originally the site of a Roman fort, Gobannium, it became a medieval walled town within the Welsh Marches...

 to Newport

Newport

Newport is a city and unitary authority area in Wales. Standing on the banks of the River Usk, it is located about east of Cardiff and is the largest urban area within the historic county boundaries of Monmouthshire and the preserved county of Gwent...

 in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

.

It begins on junction of the A40

A40 road

The A40 is a major trunk road connecting London to Fishguard, Wales and officially called The London to Fishguard Trunk Road in all legal documents and Acts...

 and A465

A465 road

The A465 is a major road in south Wales. It is more commonly known as the Heads of the Valleys Road because it joins together the north ends of the South Wales Valleys...

 south of Abergavenny and then travels southwards towards Little Mill

Little Mill

Little Mill is a village in Monmouthshire, south east Wales, United Kingdom. The village has grown in size in recent years and has as a result a population of over 1,000.- Location :...

 north of Pontypool

Pontypool

Pontypool is a town of approximately 36,000 people in the county borough of Torfaen, within the historic boundaries of Monmouthshire in South Wales....

. This section is a single carriageway and is notoriously winding and undulating. From Little Mill onwards the road becomes a dual carriageway

Dual carriageway

A dual carriageway is a class of highway with two carriageways for traffic travelling in opposite directions separated by a central reservation...

, passing Pontypool and Cwmbran

Cwmbran

Cwmbrân is a new town in Wales. Today forming part of the county borough of Torfaen and lying within the historic boundaries of Monmouthshire, Cwmbrân was established in 1949 to provide new employment opportunities in the south eastern portion of the South Wales Coalfield. Cwmbrân means Crow...

 before crossing the city boundary into Newport. Here the road has a junction (25A) with the M4 motorway

M4 motorway

The M4 motorway links London with South Wales. It is part of the unsigned European route E30. Other major places directly accessible from M4 junctions are Reading, Swindon, Bristol, Newport, Cardiff and Swansea...

 and south from there loses its primary status and becomes an urban road. The first section of which, called Heidenheim Drive, is an elevated roadway through the Crindau

Crindau

Crindau is an older inner-city area just north of the city centre in Newport in south-east Wales. It lies within the Shaftesbury electoral district and community ....

 district. It then becomes a surface street called Kingsway that passes through the city centre, and continues on as Usk Way until its junction with the A48

A48 road

The A48 is a major trunk road in Great Britain. It runs from the A40 at Highnam west of Gloucester to the A40 at Carmarthen. Before the construction of the M4 motorway and the first Severn Bridge in the mid 1960s it was the principal route into South Wales. For most of its journey through Wales,...

 Southern Distributor Road

Southern Distributor Road

The Southern Distributor Road is a principal distributor road in Newport that runs from the Coldra roundabout in the east of Newport to Tredegar Park M4 Junction 28) in the west of Newport and includes City Bridge, a bow-string arch bridge spanning the River Usk...

in the south of the city.