Single carriageway

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The A511 in Leicestershire, England: a typical single-carriageway arterial road with one traffic lane for each direction (and, in this case, a two-way pedestrian and cycle way alongside) A511road004.JPG
The A511 in Leicestershire, England: a typical single-carriageway arterial road with one traffic lane for each direction (and, in this case, a two-way pedestrian and cycle way alongside)

A single carriageway (British English) is a road with one, two or more lanes arranged within a one carriageway with no central reservation/median strip to separate opposing flows of traffic. A single-track road is a type of single carriageway with a single lane with passing places for traffic in both directions. An undivided highway (American English) is the term used for motorways with two or more lanes with no central reservation/median strip. Road traffic safety is generally worse for high-speed single carriageways than for dual carriageways due to the lack of separation between traffic moving in opposing directions. [1]

Contents

Countries

Examples of carriageway variations Uk carriageway guide.png
Examples of carriageway variations

Ireland

The term single carriageway is used for roads in Ireland. Speed limits on single-carriageway roads vary depending on their classification: national primary roads and national secondary roads have a general speed limit of 100 km/h (60 mph), while regional roads and local roads have a general speed limit of 80 km/h (50 mph). In urban areas, the general speed limit is 50 km/h (30 mph).

United Kingdom

The maximum UK speed limit for single-carriageway roads is lower than the maximum for dual-carriageway roads. The National Speed Limit, which is lower for built-up areas, only applies in places where a lower numeric speed limit is not in place. The UK has one major single-carriageway motorway, the A38(M), but a number of link roads at motorway interchanges are single-carriageway.

United States

No equivalent term exists in American English. A single carriage motorway in the U.S. would be termed an "undivided highway"; this is likely to mean a multi-lane road with only striping (paint) (but no median) between the two directions of traffic flow. A road with two lanes of traffic moving in opposite directions would be called a two-lane road.

In keeping with the U.S. Department of Transportation's Manual on Uniform Traffic Control Devices (MUTCD), since the early 1970s, all numbered highways in the U.S. are striped by color to show the direction of traffic flow. Two-way undivided roads have a yellow center line (and, if there are baseline shoulder stripes, they are solid white on both sides). This center line may be solid, broken, or a combination of the two, with the different styles, denoting whether passing (which requires a driver to move into the lane used by oncoming traffic) is permitted at a given location.

Multilane roads use broken white lines between lanes moving in the same direction; at least one solid yellow line lies to the left of the lane which borders traffic moving in the opposite direction, and the right sideline is solid white. Drivers can always tell the direction of the traffic flow by looking at the striping coloration.

Undivided highways with central turn lanes

Since successful experiments in the late 1960s,[ citation needed ] some urban undivided highways in the U.S. have had a central left-turn lane used by both directions of flow. Essentially, this configuration puts a turning lane in the position of where a median would be if the road were divided.

These roads almost always have an odd number of lanes overall, usually five (two lanes in each direction with a central turning lane), but three-lane and seven-lane versions are not uncommon. Central turn lanes are most frequently built in suburban commercial areas where there are a large number of closely spaced driveways (or minor streets).

See also

Related Research Articles

<span class="mw-page-title-main">A38(M) motorway</span> Motorway in Great Britain

The A38(M), commonly known as the Aston Expressway, is a motorway in Birmingham, England. It is 2 miles (3.2 km) long and was opened on 24 May 1972. It connects the M6 motorway to Aston and Central Birmingham and forms part of the much longer A38 route.

<span class="mw-page-title-main">Dual carriageway</span> Type of road

A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.

<span class="mw-page-title-main">Median strip</span> Reserved area that separates opposing lanes of traffic on divided roadways

A median strip, central reservation, roadway median, or traffic median is the reserved area that separates opposing lanes of traffic on divided roadways such as divided highways, dual carriageways, freeways, and motorways. The term also applies to divided roadways other than highways, including some major streets in urban or suburban areas. The reserved area may simply be paved, but commonly it is adapted to other functions; for example, it may accommodate decorative landscaping, trees, a median barrier, or railway, rapid transit, light rail, or streetcar lines.

<span class="mw-page-title-main">Reversible lane</span> Lane in which traffic may travel in either direction

A reversible lane is a managed lane in which traffic may travel in either direction, depending on certain conditions. Typically, it is meant to improve traffic flow during rush hours, by having overhead traffic lights and lighted street signs notifying drivers which lanes are open or closed to driving or turning.

<span class="mw-page-title-main">Raised pavement marker</span> Road safety device

A raised pavement marker is a safety device used on roads. These devices are usually made with plastic, ceramic, thermoplastic paint, glass or occasionally metal, and come in a variety of shapes and colors. Raised reflective markers, such as plastic, ceramic, or metal ones, include a lens or sheeting that enhances their visibility by retroreflecting automotive headlights, while glass road studs gather automotive headlights with a dome shape and reflect the lights with a reflective layer within. Some other names for specific types of raised pavement markers include convex vibration lines, Botts' dots, delineators, cat's eyes, road studs, or road turtles. Sometimes they are simply referred to as "reflectors".

<span class="mw-page-title-main">Road hierarchy</span> Hierarchy in road traffic

The road hierarchy categorizes roads according to their functions and capacities. While sources differ on the exact nomenclature, the basic hierarchy comprises freeways, arterials, collectors, and local roads. Generally, the functional hierarchy can more or less correspond to the hierarchy of roads by their owner or administrator.

<span class="mw-page-title-main">Limited-access road</span> High-speed road with many characteristics of a controlled-access highway (freeway or motorway)

A limited-access road, known by various terms worldwide, including limited-access highway, dual-carriageway, expressway, and partial controlled-access highway, is a highway or arterial road for high-speed traffic which has many or most characteristics of a controlled-access highway, including limited or no access to adjacent property, some degree of separation of opposing traffic flow, use of grade separated interchanges to some extent, prohibition of slow modes of transport, such as bicycles, horse-drawn vehicles or ridden horses, or self-propelled agricultural machines; and very few or no intersecting cross-streets or level crossings. The degree of isolation from local traffic allowed varies between countries and regions. The precise definition of these terms varies by jurisdiction.

<span class="mw-page-title-main">Head-on collision</span> Traffic collision type

A head-on collision is a traffic collision where the front ends of two vehicles such as cars, trains, ships or planes hit each other when travelling in opposite directions, as opposed to a side collision or rear-end collision.

<span class="mw-page-title-main">Controlled-access highway</span> Highway designed for high-speed, regulated traffic flow

A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway, and expressway. Other similar terms include throughway or thruway and parkway. Some of these may be limited-access highways, although this term can also refer to a class of highways with somewhat less isolation from other traffic.

<span class="mw-page-title-main">Road signs in the United Kingdom</span> Overview of road signs in the United Kingdom

Road signs in the United Kingdom and in its associated Crown dependencies and overseas territories conform broadly to European design norms, though a number of signs are unique: direction signs omit European route numbers, and road signs generally use the imperial system of units, unlike the rest of Europe. Signs in Wales and parts of Scotland are bilingual.

<span class="mw-page-title-main">Carriageway</span> Width of road on which a vehicle is not restricted by any physical barriers

A carriageway or roadway consists of a width of road on which a vehicle is not restricted by any physical barriers or separation to move laterally. A carriageway generally consists of a number of traffic lanes together with any associated shoulder, but may be a sole lane in width.

<span class="mw-page-title-main">2+1 road</span> Design of road

2+1 road is a specific category of three-lane road, consisting of two lanes in one direction and one lane in the other, alternating every few kilometres, and usually separated with a steel cable barrier. The second lane allows faster-moving traffic to overtake slower vehicles at regular intervals. Traditional roads of at least 10 metres (33 ft) width can be converted to 2+1 roads and reach near-motorway safety levels at a much lower cost than an actual conversion to motorway or dual carriageway.

<span class="mw-page-title-main">Two-lane expressway</span> Expressway or freeway with only one lane in each direction

A two-lane expressway or two-lane freeway is an expressway or freeway with only one lane in each direction, and usually no median barrier. It may be built that way because of constraints, or may be intended for expansion once traffic volumes rise. The term super two is often used by roadgeeks for this type of road, but traffic engineers use that term for a high-quality surface road. Most of these roads are not tolled.

<span class="mw-page-title-main">A5103 road</span> Road in Manchester

The A5103 is a major road in England. It runs from Piccadilly Gardens in Manchester city centre to junction 3 of the M56 motorway and is one of Manchester's principal radial routes.

Driving in the United Kingdom is governed by various legal powers and in some cases is subject to the passing of a driving test. The government produces a Highway Code that details the requirements for all road users, including drivers. Unlike most other countries in the world, UK traffic drives on the left.

This article describes the highway systems available in selected countries.

<span class="mw-page-title-main">Roads in Hungary</span>

Public roads in Hungary are ranked according to importance and traffic as follows:

<span class="mw-page-title-main">Speed limits in France</span> Overview of speed limits in France

French roads have a variable maximum speed limit that depends on weather conditions. In dry weather, roads in urban areas have a default speed limit of 50 km/h, and outside urban areas have the following limits:

<span class="mw-page-title-main">Glossary of road transport terms</span>

Terminology related to road transport—the transport of passengers or goods on paved routes between places—is diverse, with variation between dialects of English. There may also be regional differences within a single country, and some terms differ based on the side of the road traffic drives on. This glossary is an alphabetical listing of road transport terms.

<span class="mw-page-title-main">Yellow line (road marking)</span> Type of road marking

Yellow lines are road markings used in various territories.

References

  1. "Single carriageway roads seven times more dangerous than motorways". The Telegraph. 24 October 2013. Retrieved 15 July 2024.