List of road-related terminology

This is a list of road-related terminology. Both professionals working for departments of transportation and roadgeeks have popularized jargon related to roads, highways, highway systems, streets, and signs.

A

Auxiliary Lane

An additional lane at the side of the mainline carriageway to provide increased merge or diverge opportunity or additional space for weaving traffic.^[1]

B

button copy

An older style of road sign using button-shaped reflectors to increase nighttime visibility of the sign.

bump

Where two routes both turn in opposite directions at an intersection. For example, Route 1 makes a turn from north to east, while Route 2 makes a turn from east to north. Thus, traffic approaching the intersection on northbound Route 1 will end up on Route 2 unless they make a right turn. Some believe that a "bump" is where a concurrency should have formed instead.

C

cloverleaf interchange

A type of interchange consisting of eight ramps, four loop ramps and four straight ramps. Each direction of a highway has two exits to the other highway, one for each direction.

concurrency

An overlap of two or more highways. Also referred to as multiplex, with duplex, triplex, etc. referring to the number of highways involved in the concurrency.

Connector Road

A collective term for interchange links, link roads, slip roads and loops.^[1]

cross-pledging

Using toll revenue obtained from one turnpike to finance another owned by the same agency. Cross-pledging is used by the Oklahoma Turnpike Authority to maintain turnpikes that could not sustain themselves.^[2]

cut-out

A shield blank whose external edge is cut to match the shape of the actual shield printed on it. Most highway shields are printed on a square blank, with a black background taking up the border space. Cut-out shields were most often used in the early days of the numbered highway systems in the United States. The standard Interstate shields are still cut-out. California is the only state that still specifies cut-out shields for U.S. and state highways.

D

decommission

To remove a highway, in whole or in part, from the state highway system. The physical roadbed typically remains usable. The highway may then receive a "lower" designation, such as a U.S. route becoming a state or county route. A decommissioned highway may not receive a new highway designation, but may become a city street or a county- or township-maintained road.^[3][4]

demountable copy

A style of road sign where each character of the sign's legend is a separate, cut out piece of metal, attached to the sign face using rivets, screws, or some other fastener. This allows for easy modification of the sign's text when needed. Used in only a few states in the U.S., notably Kansas.

diamond interchange

A common type of interchange involving four ramps, one in each quadrant. Diamond interchanges are simple to build, requiring a relatively small number of ramps, only one bridge, and allow all possible movements. However, the intersection of the ramps with the non-freeway road require some form of traffic control, like a traffic light or stop signs, making them less suited to interchanges with heavy traffic.

dumbbell interchange

A variation of the diamond interchange with roundabouts where the ramps intersect the non-freeway road. Most often found in the U.K. Named as such because the two roundabouts and the bridge connecting them resemble a dumbbell when seen from an aerial view.

duplex

See concurrency.

F

Fork

An at-grade junction of two roads, usually within an interchange, which diverge from the approach road at similar angles. Usually both diverging roads have equal status. (For a fork junction, as defined in BS 6100: Subsection 2.4.1, the minor road deviates from the straight major road.) ^[1]

G

Ghost Island

An area of the carriageway suitably marked to separate lanes of traffic travelling in the same direction on both merge and diverge layouts. The purpose of the ghost island at a merge is to separate the points of entry of two slip road traffic lanes. At a diverge it is to separate the points of exit to a slip road.^[1]

I

Interchange

A grade separated junction that provides free flow from one mainline to another.^[1]

Interchange Link

A connector road, one or two way, carrying free flowing traffic within an interchange between one level and/or direction and another.^[1]

J

jughandle

A ramp used to facilitate turns, especially left turns. Most often used in New Jersey, with a few in the surrounding states.

L

Lane Gain

A layout where a merging connector road becomes a lane or lanes of the downstream main carriageway.^[1]

Lane Drop

A layout where a lane or lanes of the upstream carriageway becomes the diverging connector.^[1]

Large Goods Vehicle (LGV): A goods vehicle, the permissible maximum weight of which exceeds 7.5 tonnes.^[1]

Link Road

In the context of junctions, a one way connector road adjacent to but separate from the mainline carriageway carrying traffic in the same direction, which is used to connect the mainline carriageway to the local highway network where successive direct connections cannot be provided to an adequate standard because the junction spacing is too close.^[1]

Loop

A connector road, one or two way, which is made up of the elements of and which passes through an angle in the range of approximately 180 to 270 degrees. The loop is considered to extend to the end of the near straight length of road contiguous with the back of the diverge or merge nose.^[1]

Low Radius

A radius between the minimum loop radius as defined in Table 4/2 of Department for Transport document TD22 and the Two Steps below Desirable Minimum Radius with Superelevation of 7% as required for the slip road or interchange link design speed.^[1]

M

Mainline

The carriageway carrying the main flow of traffic; generally traffic passing straight through the junction or interchange.^[1]

Michigan left

A maneuver required when a left turn is prohibited, as in much of the U.S. state of Michigan, which involves turning right at the desired street and making a U-turn.

multiplex

See concurrency.

N

neutered shield

An Interstate shield which lacks the name of the state above the route number.

Nose

A paved area, approximately triangular in shape, between a connector road and the mainline at a merge or diverge, suitably marked to discourage drivers from crossing it.^[1]

P

Parallel Merge/Diverge

A layout where an auxiliary lane is provided alongside the mainline carriageway.^[1]

partial interchange

An interchange that is missing one or more ramps, making some movements impossible. Partial interchanges are built when consecutive interchanges are spaced too tightly to allow all ramps to be built safely, or when a movement would make no sense (such as going from eastbound I-240 to westbound I-40 in Oklahoma City) or would be executed rarely enough that it would not justify the cost of building the ramp, of which is common for leftover bifurcations for former endpoints of a freeway before being extended, though some deviations like that are eliminated too when the freeway is extended. Some toll roads also use partial interchanges in order to force traffic through toll plazas, either located on the ramps themselves or further down the road.

R

Reserved Lane

A lane carrying traffic that is segregated from weaving traffic.^[1]

roadgeek

A hobbyist who enjoys traveling and/or studying roads and or road systems. Also road enthusiast or roadfan.

Rural Road

An all-purpose roads and motorways that are generally not subject to a local speed limit.^[1]

S

Slip Road

A connector road within a junction between a mainline carriageway and the local highway network, or vice versa, which meets the local highway network at-grade. Traffic using a slip road usually has to give way to traffic already on the mainline or on the local highway network.^[1]

SPUI

Abbreviation for single point urban interchange. A variant of the diamond interchange most often used in urban areas that only requires one traffic signal.

T

Taper Merge/Diverge

A layout where merging or diverging traffic joins or leaves the mainline carriageway through an area forming a funnel to or flare from the mainline carriageway.^[1]

terminus

The end point of a highway. Signage denoting the end of the route may be present at the terminus.

Texas U-turn

A lane allowing cars traveling on one side of a one-way frontage road to U-turn into the opposite frontage road (typically crossing over or under a freeway or expressway) without being stopped by traffic lights or crossing the highway traffic at-grade. Also referred to as a Texas Turnaround.

"Tiger Tail"

A ghost island layout at a diverge utilising TSRGD diagram 1042.1 to separate the points of exit to a slip road. So called because the vertical sign used to inform drivers of the layout incorporates an illustration that resembles a tiger’s tail.^[1]

A TOTSO junction

TOTSO

"Turn off to stay on"—a term used when one has to turn off the main carriageway to stay on the route being followed (such as junction 5 of the M25). This term was developed by the Society for All British and Irish Road Enthusiasts and has been adopted by similar groups in Germany^[5] and in the Netherlands^[6] and warrants a mention in Wikipedia in those countries.^{NL, DE} The term has also made an appearance in the British National Press.^[7]

trumpet interchange

A type of interchange used for a "T"-junction where a road or highway ends at a freeway.

U

Upstream

That part of the carriageway(s) where traffic is flowing towards the section in question.^[1]

Urban All-Purpose Road (UAP)

An all-purpose road within a built up area, either a single carriageway with a speed limit of 40 mph (65 km/h) or less or a dual carriageway with a speed limit of 60 mph (100 km/h) or less.^[1]

Urban Motorway

A motorway with a speed limit of 60 mph (100 km/h) or less within a built up area.^[1]

useless concurrency

A concurrency between a highway's terminus and the point where it splits off on an independent alignment. The concurrency is "useless" because the highway could have just as well ended at the point it intersected with the concurrent road, rather than being extended to some other point by means of a concurrency. useless concurrencies also occur when a numbered 2-lane road paralleling a freeway is sufficient enough for state highway standards, though Interstate business loops that are concurrent with a parallelling state or US highway cease to be "useless" as the short business loop serves a practical purpose.

W

Weaving Section

The length of the carriageway between a successive merge or lane gain and diverge or lane drop, where vehicles leaving the mainline at the diverge or lane drop have to cross the paths of vehicles that have joined the mainline at the merge or lane gain.^[1]

wrong-way concurrency

A concurrency between two roads with opposite signed directions, e.g. a westbound highway and an eastbound highway. Often, the physical roadbed is actually headed in a totally different cardinal direction. Some wrong-way concurrencies are often regarded as "useless concurrencies" too.

References

External links

• AARoads Glossary