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For the newcomer to the 'roads community' or to the visitor with a casual interest, the increasingly complex and detailed terminology gets quite confusing. Isn't a 'multiplex' a big cinema? Surely a 'trumpet' is a musical instrument? And shouldn't you see a doctor if your 'nose' has a merge?

Catenary LightingCBRD comes to the rescue with the Dictionary — something approaching a comprehensive glossary of the terms currently used by those discussing British roads. Some are engineering terms, some were created by road enthusiasts, some have multiple meanings. All are defined here as clearly as possible.

If there's something you think should be here but isn't, then let me know and I'll add it to the list. And if you're looking for the meaning of terms like D3 or S2, there's a separate page about abbreviations.

The following list is, allegedly, in alphabetical order. Click a word to jump to its definition.



  1. Concerning junctions, access refers to whether or not you can reach a certain road or direction from a given approach to the junction. A junction where not all roads are accessible from all others is limited-access. See also movements.
  2. Road-sign term used to designate restrictions on the use of a road: "No access for buses and coaches" or "No entry except for access". This always suggests the question: access to what? The houses on this street? The street at the other end? Lincolnshire? Legally, it refers to property adjoining the affected road that is not reachable by any other route, but these restrictions are rarely, if ever, enforced.

Access Controlled

Closely related to the idea of grade-separation. A road which is access controlled is one which can only be entered or exited at certain points, to enable traffic on the road to move more smoothly. Usually this means that minor or private access points are closed off.

Active Traffic Management (ATM)

A system used on certain motorways where gantry signs are computer-controlled to set a variable speed limit, open the hard shoulder as a running lane and limit the volume of traffic entering at junctions, with the aim of improving the flow of traffic.

Image Feature on Active Traffic Management

See also controlled motorway; Variable Speed Limit.


ADSAn acronym for "advance direction sign" — the large billboard-style signposts erected before reaching an important junction.

All-Purpose Road

The opposite of a motorway: a road which can be used by any traffic, not just motorised vehicles. Virtually all motorable roads in the UK can be described as all-purpose roads.


Roads whose numbers are prefixed with the letter 'A'. A-roads denote the best and most-used all-purpose roads in the UK. Because of inconsistent upgrades over the years, an A-road can now vary from a single-track mountain road in Wales to a grade-separated motorway standard eight-lane dual carriageway like the A2 in Kent.

To make the system clearer, in the 1960s primary status was introduced, splitting the A-road system into two tiers. A-road numbers can be one, two, three or four digits in length.

See also B-Roads.


Used to describe a major road which forms a route through or past settlements. The M1, for example, is an arterial road through the East Midlands, serving Leicester, Derby, Nottingham and Loughborough. In the 1930s road-building boom, many of the road schemes of the time were referred to as artierial, and the word even made it into the official road names, such as on the A127 Southend Arterial Road.

See also bypass; radial.

Asymmetric Widening

A technique used when widening a road, where the extra width is added to just one side of the existing paved surface.

See also symmetric widening; parallel widening.


An interchange where all the roads concerned meet at one level, requiring traffic from some or all directions to come to a stop. The opposite of a grade-separated junction.


Ax(M)A term used to refer to the UK's oddest road classification, the "A-Road with Motorway regulations". These roads are usually bypasses to a section of a longer A-road which is under motorway restrictions. Such roads are given the A-road's number, with (M) appended, hence the term Ax(M). They are, in every other sense, motorways.


Belisha Beacon

Belisha BeaconPossibly the most British of all roadside items. Belisha Beacons are the flashing orange globes on black and white poles that mark zebra crossings. Named for Leslie Hore-Belisha, the Minster of Transport 1934-37, who oversaw their introduction.

Image Feature on Zebra Crossings


The point where a flow of traffic splits in two, most commonly where a sliproad exits the mainline of a road. On British roads, the large two-headed arrow painted on the road surface at these points is called the "bifurcating arrow".

See also diverge.

Black Spot

Colloquial term used to describe a particularly dangerous junction or section of road where incidents frequently occur. Often referred to as an "accident black spot".


bottleneckA junction or section of road that has lower traffic capacity than the road either side, and is therefore a cause of frequent congestion.


Second-class roads whose number is prefixed with the letter 'B'. Less wide-ranging than other classes of road, B-roads tend to be either minor country roads connecting villages, or town and city streets. B-road numbers are only ever three or four digits long.

See also A-roads.

Bus Gate

A method of discouraging through traffic in town and city centres. Bus gates are short sections of road which are blocked off to all traffic except buses (and sometimes taxis too).

See also pedestrianise; bus lane.

Bus Lane

A lane reserved for the use of buses, and commonly also taxis and bicycles. They are usually found on major roads in and out of cities to allow public transport to avoid traffic jams, and it is illegal for other types of traffic to use them. They typically operate only for certain hours of the day.

See also bus gate.


BypassA diversion of a major road to carry traffic around a built-up area, in order to improve the journey of through traffic and improve the environment along the original route.

See also arterial; radial.



The sloped surface of a carriageway: the camber refers to the way the carriageway is sloped towards one or both edges to allow rainwater to run off easily. Usually the peak is at the centre.

See also crossfall; superelevation.


CannonWhere two roads meet and, instead of crossing each other, bounce off in a similar way to what happens when two billiard balls run into each other. If you're still not sure, imagine a simple four-way crossroads. Road A and road B meet here. If they cannoned, road A might come in from the north and exit to the east, and road B might come in from the west and exit to the south.


The surfaced part of a road intended for wheeled traffic. A carriageway can be made up of any number of lanes, though the two terms are often confused.

See also single carriageway; dual carriageway.

Catenary Lighting

Catenary LightingA special type of road lighting where the lamps are suspended on a high-tension wire suspended from a row of masts in the central reservation of a dual-carriageway.

C/D lanes

See Collector/Distributor Lanes.

Central Reservation

The dividing strip between two carriageways, and therefore a central feature of a dual carriageway (pun not intended). The American term is a median.

Chainage Marker

An alternative name for a Marker Post. This name is now technically incorrect as marker posts express distances in kilometres, though on British railways distances are still measured in chains.

See also driver location sign.


A term to describe any road that has a number.


ClearwayThe name given to a road other than a motorway where stopping, except in an emergency or a specified parking place, is completely forbidden. These roads are marked with special 'clearway' signs: a blue circle with a thick red border, crossed with two diagonal red lines.


A type of four-way free flowing interchange, which is distinctive for its four loops.

Image Feature on Cloverleaf junctions

Collector/Distributor lanes

Usually abbreviated to C/D lanes. The term refers to additional lanes, usually on a separate carriageway, which run alongside the mainline of a road through a large grade-separated junction. Their purpose is to separate the entering and exiting traffic to avoid disruption to through-traffic where there are several junctions in quick succession.


  1. Another way of referring to the nine numbering zones that are used to allocate route numbers in the mainland UK.
  2. Red-orange coloured plastic obstacles used to divert traffic in roadworks or at temporary obstructions to a road. But you knew that already.


Used when describing a junction. Conflict refers to a point where flows of traffic going in different directions must compete with each other for road space: for example, the point where a road feeds on to a roundabout is an obvious point of conflict. The less conflicts a junction has, the more smoothly it will flow. Free-flow junctions omit almost all conflicts; grade-separated junctions remove conflicts from the main through route.


A situation where the volume of traffic is too great for the road and vehicles must slow down or stop. It is frequently caused by bottlenecks, poor junction design and traffic incidents.

See also queue; traffic jam.

Congestion Charge

A toll or fine which is levied on vehicles, put in place to reduce traffic because of large-scale congestion. London now has an experimental congestion charging scheme in the city centre, where passenger cars wishing to enter the area inside the inner ring road must pay a toll. A similar scheme exists in Durham and other cities are looking to introduce them too.

Image Feature on the London Congestion Charge


  1. A technique used when carrying out maintenance on a dual carriageway when the work means that several lanes or a full carriageway must be closed. It involves temporarily transferring traffic in both directions onto just one carriageway to allow the other to be partly or fully closed.
  2. A permanent lane of traffic which flows in the opposite direction on an otherwise one way street: this is almost always a contraflow bus lane or a contraflow cycle lane.

Controlled Motorway

A motorway where a computerised system involving traffic-detection loops embedded in the carriageway and variable message signs above lanes are used to regulate and control the traffic flow.

See also Active Traffic Management; Variable Speed Limit.

Crawler Lane

Crawler LaneWhere a major road goes steeply uphill, sometimes a crawler lane is installed in addition to any other lanes on the road, for the use of slow vehicles. It leaves the main traffic lanes free for faster traffic.


A road whose number is prefixed with a letter other than A, B or M. C-roads are not signposted or shown on maps; they are reference numbers used by the government bodies that maintain roads. Prefixes range from the most common 'C' to 'D' and 'U'.

Image Feature on C-Roads

See also A-Road; B-Road; unclassified.


The angle of slope, relative to the horizontal, of a road's surface.

See also camber; superelevation.


A simple four-way junction where two roads cross roughly at right angles. Twice as good as a T-junction.

Cycle Lane

A lane on a carriageway reserved exclusively for the use of bicycles. Some are marked by solid white lines and may not be used by other traffic; others are marked by broken lines and are only advisory. Often it is legal for other vehicles to park in an advisory cycle lane or to travel in it when necessary.



DefunctThe state of a road number that was once in use, but is now not allocated to a road.

Department for Transport

The national government body responsible for transport in Britain, and therefore in overall control of the roads. It has no direct involvement, and its responsibilities are carried out by a range of agencies and local authorities.

This responsibility has previously been held by the Roads Board; Ministry of Transport; Department of the Environment; Department of Transport; Department for the Environment, Transport and the Regions; Department for Transport, Local Government and the Regions.


The process of removing trunk status from a road, so it becomes the responsibility of local authorities.

See also trunk road.


A very basic type of grade separated interchange.

Image Feature on Diamond junctions


An acronym for "Defunct In Original Location". Simon Mold came up with this word to give the folk of SABRE a way of describing one of their favourite types of historical roads.

Distributor Road

A road which serves to take traffic from the terminus of a major road and carry it to a large number of exit points, preventing all the traffic being unloaded at just one point. It can also mean a road which carries large volumes of traffic and disperses them through a large urban area, again with the aim being to prevent all the traffic entering the urban area at one single point.

One of the M27's many functions is to act as a distributor road for the M3, allowing its traffic load to be spread around northern Southampton rather than have it all unloaded onto the A33.


The point where two streams of traffic split and go in different directions.

See also merge; nose.


  1. An official temporary detour from the usual line of a road. Diversions are usually set up because of a temporary road closure, often for roadworks.
  2. In legal orders, "diversion" is used to describe a permanent change in the line of a road, such as for a bypass around a settlement.


See Department for Transport.


Lowering the status of a road — by giving it a different, less important number or by making physical alterations — in order to discourage its use as a through route. Usually this is done when a newer route is built nearby: for example, the M40 was opened in 1991 and as a result A-roads nearby were downgraded, the A34 to A3400 and A41 to B4100. It is not quite the opposite of an upgrade.

Driver Location Sign

A new type of sign, placed at regular intervals at the side of the motorway, designed to provide the same information as marker posts in a more visible form. CBRD has a special feature on them.


See lane drop.

Dual Carriageway

Dual CarriagewayA road with two separate road surfaces side by side, with a central reservation to divide them, usually in the form of a grassed strip or crash barrier. In almost all cases the two carriageways are used to separate traffic moving in different directions. It is also known, particularly in the US, as a divided highway. Note that the term 'dual carriageway' is not related to the number of lanes a road has.

See also single carriageway; carriageway.


The process of turning a road into a dual carriageway.


A type of grade-separated interchange. It can take two forms:

  1. One that uses a roundabout at each side of the major road linked by a bridge.
  2. A similar scenario to the above, but with an elongated roundabout spanning the major road, pinched together in the middle to use a single bridge or underpass.

Image Feature on Dumbbell junctions


A situation where a road numbering anomaly or error has resulted in two separate roads holding the same number. The number is said to be duplicated.


E-routes (or E-roads)

A road with a number prefixed with 'E'. E-routes are a pan-European network composed of existing roads, called the TERN (Trans-European Road Network). Most European countries co-sign the E-routes with their existing road numbers, but in Britain E-routes are never signposted, largely because Britain has no land borders and therefore they are somewhat redundant. They do, nevertheless, exist: the E-15, for example, is better known as the A1 and the E-13 the M1. E-routes connect to mainland Europe by vehicle ferries.

In the 1970s the Department of Transport refused to signpost E-routes unless the network was entirely routed onto motorways: impossible since the motorway network, even today, is fragmented! This can probably be interpreted as a long-term delaying tactic. For a time, the design for a sign to display E-routes existed in the TSRGD, but it was never used.

Wikipedia has a map of E-routes in the UK and an article on the international E-route network.


ElevatedA road supported on pillars to raise it above ground level. This is most commonly found on urban motorways to enable them to cross surface streets more easily, though it is sometimes done in order to traverse an unusual geographical feature: to hold a road above unstable ground, for example, or run it along a steep hillside.


A point at which you can join a road. Usually this applies to access controlled roads.

See also exit.

Escape Road (or Escape Lane)

A short road, usually lined with a deep layer of gravel, found at the bottom of steep hills to catch runaway vehicles that are unable to stop.


A point at which you can leave a road. Usually this applies to access controlled roads.

See also entry.


Filter Arrow

Filter ArrowA green arrow on a traffic light used to allow some turning movements at a signal controlled junction during the red phase.

Filter Lane

A handy little lane used to turn left at a junction, frequently at roundabouts or traffic lights, which avoids using the junction itself.


A bridge carrying one road over the top of another.

See also overbridge; overpass; underpass.


An interchange where all the roads involved are grade separated and all movements between them are served by sliproads. A junction is only free-flowing if all of the turning movements through the junction are carried on sliproads and different streams of traffic merge rather than come to a stop.

See also grade separated.



See lane gain.


GantryA platform elevated across all or part of a carriageway to support overhead signs, Variable Message Signs or traffic lights.


A particular type of speed camera — possibly the most prevalent type in the UK. Gatso is an abbreviated form of "Gatsometer", the name given to the camera by its Dutch manufacturers.

Give Way

Give WayA peculiarly British term used on the most popular road sign. "Give Way signs" are found where one road terminates on another, and inform traffic that it must cede priority to other traffic. Give Way is a shortened version of "give right of way". Before the Worboys report, these signs read "Slow — Major Road Ahead", which means that "Give Way" is a marked improvement in clarity.

See also stop.


The American term for the nose of a diverge.

Grade separated

Grade Separated
  1. A stretch of road that does not meet any other road or obstacle on the level. Other roads, railways, footpaths and so on are carried over or under the road using bridges. Junctions on this type of road must also be grade separated.
  2. An interchange where the major route or routes through the junction do not stop and do not cross any other road on the level. Movements to other roads are made using sliproads and bridges to avoid conflicts.

See also free-flow.

Grade separation

The process of making a road or junction grade separated.


A very vague term — in many cases simply referring to a large roundabout. It is a name usually applied to large traffic-light controlled roundabouts or circulatory systems made up of existing roads.



Part of a road numbering system specific to the new town of Milton Keynes. The town was designed with an American grid road system. 'H' stands for Horizontal and designates a road that runs east to west. H-roads all have names that end in "Way" and are numbered from H1 in the north to H10 in the south. The H-roads and their V counterparts are marked on relevant roadsigns, particularly where they intersect.

See also V-Road.


HamburgerA descendant of the roundabout, where one road travels across the central island of the junction. All other traffic and turning movements must use the roundabout. From overhead, the junction resembles a hamburger. This type of junction is, almost without exception, signal controlled. A good example is at M602 J3.

Hard shoulder

An auxiliary lane at the left of the carriageway, set aside for stopped vehicles and emergency services to ensure the main running lanes on the carriageway remain free from obstructions. On motorways it is illegal to stop on a hard shoulder except in an emergency.

Hard Strip

A metre-wide extension of the paved road surface beyond the edge of the carriageway on roads that lack a hard shoulder. Hardstrips are sometimes signed as cycle lanes, but they're really too narrow for this and often littered with drainage gullies and other metalwork, not to mention the detritus that collects at the side of any road.


See Highways Agency Traffic Officer.


HeadroomA term used on road signs warning of low overhead clearance. Headroom is the space available above the road surface before hitting a solid object like a bridge. Posting warnings helps to prevent vehicles hitting a solid object like a bridge.

Highways Agency

The Highways Agency is the government agency in direct control of trunk roads in England. It is an executive agency of the Department for Transport.

Highways Agency Traffic Officer

Usually abbreviated to HATO. These officials have been recruited to take over some of the Police's former responsibilities in managing the motorway network. They handle non-emergency work, such as aiding broken down traffic and assisting with traffic management when incidents occur. They are often colloquially referred to as "traffic wombles", a reference to the furry children's TV characters who cleared up rubbish.


  1. The central point at which radials start.
  2. The basic central point of the road numbering network. London and Edinburgh are Britain's hubs. The various zones radiate from these two cities.

Hybrid junction

A junction, or more usually an interchange, with a unique layout which is composed of components that are recognisably part of more common junction types.



A junction by any other name. The word interchange is usually used to describe a large, complex or grade separated junction.

Image Feature on Interchanges

Invented Number

A road number that, instead of being created as part of a sequence, has been allocated because it sounds memorable. Examples include the A5300, which is part of the Liverpool ring road. There is no A5301 or A5299, at least not nearby.


  1. A raised area designed to deflect or divide traffic, or to make it easier for pedestrians to cross the road, found in the centre of an area of carriageway. The central part of a roundabout is an excellent example of an island. They are often also referred to as traffic islands.
  2. In slang used in parts of the West Midlands and North West England, a roundabout.



A place where two or more roads meet, regardless of how it is laid out or designed.

See also interchange.



KerbThe raised section at the edge of the carriageway, used to channel rainwater and perhaps stop stray vehicles. Americans spell it "curb", but in British use that spelling only applies to the verb.



A section of a carriageway marked out for use of traffic, usually only in one direction. Carriageways are frequently described by their width in terms of lanes.

See also running lane.

Lane Drop

Where a sliproad leaves the main carriageway of a road, taking one or more of the lanes with it, causing the main carriageway to narrow. Those lanes are said to have been dropped.

See also lane gain.

Lane Gain

A situation where one or more lanes permanently join the main carriageway from a sliproad, causing it to be wider from that point on. The lanes have been gained.

See also lane drop.

Level Crossing

Level CrossingA place where a road crosses a railway at the same level, requiring road traffic to stop when a train approaches. These come in a variety of flavours: some have automatic barriers, others have manually operated gates and a few have only a set of flashing lights.

Limited Access

A grade separated junction where vehicles can only access the major road in certain directions and other movements are blocked.


A term used on SABRE to refer to the all-capitals lettering used on British road signs prior to the Worboys Report, named for the committee responsible for its design.


LongaboutFor practical purposes this is a type of junction that operates like a stretched-out roundabout. In actual fact it is usually a section of dual carriageway with two one-way gaps in the central reservation that has been appropriated to form one large junction by giving it the priority rules of a roundabout. There is a good example on the A414 in Hertfordshire.

Long-Way-Around Route

Aside from its obvious meaning, in road numbering terms this refers to a numbered route which does not provide the most direct way between its start and end points. A good example is the A404, which starts in central London and ends west of Maidenhead, but on the way goes almost as far north as Watford.


  1. A type of sliproad that curves round a very long way. Often used to turn right by turning a very long way left. Think about it.
  2. Electronic sensor equipment that is buried in the road surface, used either to count vehicles passing over it or to adjust traffic light timings at a nearby junction. Its full name is an inductive loop. Red-light cameras are triggered by loops placed just beyond the stop line. They are also vital to the operation of controlled motorways.

Low Emission Zone (LEZ)

A scheme introduced across Greater London in 2008 that imposes fines on the most polluting large vehicles. It is part of an experimental scheme that includes similar zones across Europe.

Image Feature on the Low Emission Zone


Magic Gyratory

A junction that is functionally the same as a magic roundabout, but has a fundamental difference in that it is much larger. Usually a magic gyratory is comprised of several normal roundabouts connected with short lengths of road. A typical magic roundabout exists on one single junction whereas a magic gyratory is more like a number of nearby junctions working together.

Magic Roundabout

Magic RoundaboutTechnically known as a Ring Junction, but that's no fun, is it? A magic roundabout is a two-way roundabouttraffic flows in both directions around the central island, and roads joining the roundabout meet it at a mini-roundabout. It sounds crazy, but these really exist.

Image Feature on Magic Roundabouts

See also magic gyratory.


The main part of a road, including lanes and carriageways in both directions, and excluding any other distractions like parallel roadways, side turnings, sliproads, Collector/Distributor lanes and so on. In short, whatever counts as "straight on".

Mainline Metering

A technique used to control the volume of traffic along a route to maximise capacity downstream. Traditionally it is done with toll gates for bridges and tunnels, but it may see application elsewhere.

See also Ramp Metering.

Marker Post

Small posts by the side of most motorways and trunk routes giving the distance from the notional start point of that road, placed at 100-metre (0.1km) intervals. They provide a reference point for highway authorities, emergency services and stranded motorists. The Highways Agency has installed larger Driver Location Signs giving this information at 500 metre intervals on some motorways. They are sometimes known as a Chainage Marker.

Matrix Signs

Matrix SignsSometimes referred to as "changeable signs" — electronic displays by the roadside that use LEDs to display a variety of messages. Small matrix signs are installed in the central reservation of motorways at one mile intervals, and larger ones are often used at big junctions or on busy sections of road.

See also variable message sign.


Where two different traffic flows come together and continue as one, designed in such a way that neither should ordinarily have to stop, though one flow usually takes priority over the other. The opposite of a diverge.


A junction with most of the benefits of a normal roundabout, but used in places where space is limited. They are theoretically little different to the American "four-way stop" concept. The central island is painted onto a raised area of the road surface and is usually no more than a few metres across, to allow long vehicles to pass over the top. They are much derided as a means of traffic control as most people simply drive straight over instead of going round, but they offer significant benefits in terms of priority rules and giving equal priority to several roads.

See also magic roundabout; traffic calming.

Misleading Sign

As opposed to a sign that is simply wrong, this concerns direction signs that intentionally omit information for one reason or another. Frequently in practice this means a road number not being displayed on a sign to discourage the use of that road.

Misplaced Number

A road number which, through normal renumbering or error, is not in the area it should be according to the road numbering pattern. This can range from roads simply out of place within their own zone (like the A403 being near Bristol) to roads numbered completely in violation of numbering rules (like the A42).


MotorwayA special type of road reserved for motorised traffic only. The UK's motorway network is comparable to Germany's Autobahns, Italy's Autostrade or America's Interstates. Motorways form a network of long-distance dual carriageways, all grade-separated and free of slow-moving or pedestrian traffic. Motorways have numbers prefixed with M or suffixed with (M).

See also regulations; urban motorway; Scottish Motorway.

"Motorway Permanent" lettering

The typeface used on motorway ADS for road numbers. It is also available in "Motorway Temporary" flavour for use with black text on light backgrounds on temporary roadworks signs.

See also Worboys; "Transport" lettering.


Used in the context of describing an interchange, a 'movement' is one of the turns or changes in direction that the interchange allows. A simple crossroads would allow all movements, but more complex motorway junctions might omit some movements that are served by other junctions or roads.

See also limited access.


MultiplexA SABRE term describing the situation where two road numbers share the same road. In Britain, only one road number may be shown on signs at once so one road must be 'dominant' over the other in a multiplex — or rather, one must be signed and the other invisible. A good example is the M60 Manchester Ring Road, which multiplexes with the M62 in the north-west. Road signs indicate that the road is the M60 leading to the M62.


National Speed Limit

NSLThe default speed limit which applies to rural roads without any other posted limit. It is 60mph on single carriageway roads and 70mph on dual carriageways and motorways. The National Speed Limit is not a signal that a road is of a standard suitable for 60 or 70mph; instead it requires drivers' own judgement as to a safe speed. It was introduced temporarily in December 1965, prior to which time 'derestricted' roads had no speed limit. The limit of 70mph was made permanent in 1967, and during the 1970s oil crisis it was lowered to 50mph. Afterwards dual carriageways were restored to 70mph, and single carriageway roads were only lifted to 60mph. Frequently abbreviated to NSL.

Natural Bypass

A road which provides a bypass for a settlement without being built as one — it simply happens to be in the right place.


The tip of a merge or diverge. In the US it's called a gore.


See National Speed Limit.


The alphanumeric tag given to a road, such as A642 or M5. Numbered roads are referred to as classified.

Road numbers provide a simple way to refer to a road and to describe a journey through the network. Each road number is unique within the network — though a different letter prefix means a different road. For example, the A621, B621 and M621 are all different roads in different parts of the country.

Image Feature on Road Numbers

See also A-roads; B-roads; C-roads; motorway; Ax(M); unclassified; zones; "misplaced" number.



OdologistSomeone with an interest in roads. See Odology.


Another way of saying 'the study of roads', derived from the classical Greek hodós (path or way) + logy (theory or study).


See off-slip.


A sliproad used to exit a road.

See also on-slip.

One Way

One WayA road that may only be used by traffic going in one direction.

See also contraflow.

On-line Improvement

An upgrade or other improvement to a road carried out on the line of the existing road. Hence on-line dualling would involve turning the existing road into a dual carriageway, rather than building a new dual carriageway alongside.


See on-slip.


A sliproad used to get on to a road.

See also off-slip.


Another word for a ring road. 'Orbital' tends only to be used for very large or important ring roads — London's industrial-strength ring road, the M25, is the original one. The term is often applied to the M60, and recently Blackburn has started signposting its own slightly less impressive ring road as an orbital too.


OverbridgeAn alternative word for a flyover. Those striving for maximum variety in their description of highway structures might also like to use the word overpass sometimes.


Another word to describe a flyover or overbridge, and clearly the opposite of an underpass.


Parallel Widening

A method of widening a road which involves building an entirely new road to one side of the existing one, and then removing the old road. Sounds radical, but it has been done before, most notably on parts of the M5 in Worcestershire which was widened from two lanes to three, requiring the removal of many bridges.

See also symmetric widening; asymmetric widening.


PedestrianSomeone who uses a road by walking along it (or otherwise uses their feet, so joggers and runners and perhaps even people hopping on one foot also count).

See also pedestrianise.


Making a street available only to pedestrian traffic — a street which is only open to pedestrians (and often also bicycles and delivery vehicles during certain hours) is therefore 'pedestrianised'.

Pegasus Crossing

A type of pedestrian crossing that provides parallel walkways across the road for pedestrians and horse riders. The crossing includes push-buttons at a high level for use of those on horseback to avoid them having to dismount.

See also pelican crossing; puffin crossing; toucan crossing; zebra crossing.

Pelican Crossing

The name given to pedestrian crossings which use traffic lights to control motorised traffic. "Pelican" is derived from the acronym given to the crossings when they were first introduced in the 1960s — a 'PeLiCon' crossing, or Pedestrian Light Controlled crossing.

Image Feature on Pelican Crossings

See also pegasus crossing; puffin crossing; toucan crossing; zebra crossing.

Pinch Point

Pinch Point
  1. A place where a road is naturally constricted and has lower capacity; a bottleneck.
  2. A deliberate narrowing of the road or lane to reduce vehicle speeds.


Some A-roads are designated as primary routes, indicating that they are more suitable for long-distance traffic. Large towns, cities and places of 'traffic importance' across the country (such as bridges or tunnels) are designated 'primary destinations'. The best routes between these places, by A-roads and motorways, are primary routes. Almost all motorways are de-facto primary routes.

An A-road is rarely entirely primary; most either never have primary status or gain and lose it along the route. The upside of this is that navigating is simple if you follow the green signs; the downside is that it makes numbering complex since few primary routes follow just one A-road.

Often confused with trunk roads.

Principal Road

  1. In everyday conversation, a loose description of a major road.
  2. A non-trunk A-road, or in other words, any A-road maintained by a local authority.


Whichever road, lane or traffic flow is more important and recieves preferential treatment at a junction or junctions is said to have priority. Usually this means it does not have to stop and that other roads or lanes — those without priority — have to stop or give way to it. The general exception is at traffic lights, where everything stops at one time or another: here priority means getting a longer green phase than other roads.

Puffin Crossing

A signal controlled pedestrian crossing, where the lights controlling pedestrians are located at the same side of the road instead of the opposite side. It also includes pedestrian detectors so that the system can customise the crossing time and even cancel the request to cross if the pedestrian presses the button and then walks away.

See also pegasus crossing; pelican crossing, toucan crossing, zebra crossing.



QueueA British standard practice, both in a wider cultural sense and in a more specific roads sense. On the British road network, a queue is what you encounter when you want to go somewhere.

See also congestion; traffic jam.



A road which carries traffic specifically to and from a large settlement. Usually a radial is defined by being one of a number of such roads which all strike out in different directions from their hub.

See also bypass; arterial.

Ramp Metering

Ramp Metering involves placing a set of traffic lights near the point where a motorway on-slip joins the mainline. The lights switch quickly from green to red and back, causing small amounts of traffic to enter the motorway in a steady flow. This prevents congestion on the major route by not allowing large volumes of traffic to join the motorway at once.

See also Mainline Metering.

Red Light Camera

A device that is designed to automatically photograph vehicles who pass red traffic lights so that they can be prosecuted. It is triggered with the use of loops in the road surface that detect vehicles crossing the stop line.

See also speed camera.

Red Route

This term seems to have any number of official and documented meanings.

  1. A type of road found only in London, marked by special "red route" signs on entering and with double red lines down the sides of the carriageway. No stopping for any reason is permitted on red routes (they are clearways with stricter rules and harsher penalties), the idea being to keep traffic and especially buses flowing on major roads. Parking and loading bays are provided in strictly marked areas. This policy has been successful in London and has recently been applied in smaller doses to Edinburgh, Glasgow and Birmingham.
  2. A rural road with a high accident rate in Lincolnshire, according to a recent campaign by the County Council there. Signs have been erected on roads like the A15 north of Lincoln to raise awareness of the likelihood of accidents on these routes.


  1. A traffic island in the centre of a road or dual carriageway, installed so that pedestrians can cross the road in two stages rather than in one for safety reasons.
  2. A gap in a central reservation provided where vehicles can wait to turn right.


Any set of laws, bye-laws or other legal paraphernalia governing the use of a road.

The term may also refer to motorway regulations. In legal terms, a motorway is not a public right of way or a public road — it is a special road. That means that legally it can only be used by motorised traffic: no pedestrians, no bicycles, no animals, no 'invalid carriages', no motorbikes under 50cc. It also covers other things like a prohibition on stopping except in emergencies.

Relief Road

Often more a political word than an engineering one. A relief road is a vague concept, usually referring to a road built to take away most of the traffic on an existing route. The concept is very similar — often indistinguishable, in fact — to a bypass.

The term 'relief road' is often employed to dress up a big ugly road built through or close to an urban area (since it promises an improvement), such as the Bingley Relief Road which would be a bypass if it didn't run right through the middle of the town.


RepeaterRepeaters are miniature speed limit signs placed at frequent intervals by the side of roads to remind motorists of the speed limit. They are required (in some cases legally) where the default speed limit does not apply — anywhere, in fact, that the limit is not the National Speed Limit in a rural area, 30mph in a built-up area or 20mph in a 20 zone.

Ring Junction

The technical name for what is normally known as a Magic Roundabout.

Ring Road

Theoretically, a circular road built around the perimiter of a built-up area as a bypass for traffic from all directions, the idea being to distribute traffic around the edge rather than squeeze it through the centre. In practice, many ring roads in Britain are incomplete — often planned that way — not just with coastal towns but in some cases because traffic volumes on the 'gap' side are not high enough, or for more complex political reasons. The name 'ring road' still applies. London's middle ring roads are called the North and South Circular Roads.

See also orbital.


RoundaboutA type of junction common in Britain, and which is often considered one of the defining features of the UK road network. Its main feature is a circular, one way roadway onto which all the roads meeting at the junction terminate. Traffic approaching the roundabout gives priority to traffic already on it. It then circulates the roundabout until the road it wishes to take. In Britain roundabouts are always clockwise, but for right-hand driving the direction must be reversed.

Contrary to popular belief, roundabouts often have higher capacity and better safety records than traffic-light coordinated junctions, because of their self-regulating nature and the impossibility to 'run' one. The best junction type depends on the exact location, of course.

See also roundabout interchange; magic roundabout; mini-roundabout; longabout.

Roundabout Interchange

A type of grade-separated junction that is truly British, incorporating as its main feature a roundabout.

Image Feature on Roundabout Interchanges

Running Lane

Any lane that is in use for general traffic. The term is usually used to distinguish the 'through' lanes from the likes of bus lanes, hard shoulders etc.



The Society for All British Road Enthusiasts: an organisation founded in 2001 that is the focus of discussion and learning on all aspects of the British and Irish road networks. The Society operates principally online through its website, www.sabre-roads.org.uk. Its members are Sabristi.


The members of the SABRE community. A term credited to the member Viator. The singular forms are Sabristo (male) and Sabrista (female).

Safety Fence

Safety FenceAny type of fencing designed to stop traffic leaving a road or crossing onto a dangerous part of one (like into a lane of traffic going the other way). These come in a wide range of shapes and sizes.

Scottish Motorway

  1. A dual two-lane motorway in Scotland built prior to 1973 without hard shoulders (in this period, hard shoulders were effectively optional in Scottish design standards).
  2. "Near-motorway standard" dual-carriageway in Scotland which would have been motorway if built or opened before 1973. Such roads are still built but can no longer be a motorway. Some have motorway-like regulations (and may be secret motorways), others are open to all traffic but operate like a motorway.

Secret Motorway

Not to be confused with A-roads that simply have motorway characteristics, such as having grade-separated junctions. A Secret Motorway is an A-road that not only prohibits certain classes of road user, but which does so by being legally designated a special road — the legal term also used for motorways. However, they still don't necessarily have motorway restrictions. Examples include the A1 east of Edinburgh and A55 around Llandudno, but in the latter example, Class IV vehicles are permitted while motorways ban them.

The whole thing is something of a minefield and is, bluntly, a term created by members of SABRE before special road legislation was fully understood!


A road which is built to the standard (or very close to the standard) of a motorway, but isn't one.

Service Area

Sometimes called a Service Station. Places found on long-distance motorways at frequent intervals providing a place for drivers to stop off the road (since stopping on a motorway is illegal). All must provide free car parking, free toilet facilities, fuel and hot food. Most are now pretty sophisticated affairs, with shops, restaurants and games arcades.

Signal Controlled

Anything that is controlled using traffic lights.

Single carriageway

A road which has one undivided carriageway for use all traffic, which is usually divided into one or more lanes for different directions of travel.

See also dual-carriageway; single-track.

Single Track

Single TrackA type of road only wide enough for one traffic lane, but which is still used for two-way traffic. Such roads are prevalent in remote countryside, and into the 21st century some primary and trunk A-roads were still to this standard.

See also single-carriageway.

Sleeping Policeman

A colloquial name for a speed bump — so called because it doesn't need to be awake to make you slow down.

See also traffic calming.

Sliproad (or slip road)

A short, usually one-way connecting road used for travelling between other roads, normally as part of a larger interchange.

Special Road

The legal term for roads that are restricted (under section 19 of the Road Traffic Act 1984) to certain classes of vehicle. Motorways are a type of special road. They are distinct from a public right of way, because while a normal right of way is open to all traffic except those specifically prohibited by order, a special road is open to no traffic except certain classes specifically allowed by order. Non-motorway roads, with motorway characteristics and subject to special road legislation, are often referred to as secret motorways.

See also regulations.

Speed Bump

Raised patches of road surface designed to slow traffic down. This term is abbreviated to "humps" on road signs. They come in several varieties, including speed tables (large humps that extend over a length of road) and speed cushions (small humps confined to one lane only, narrow enough that buses and emergency vehicles pass over unaffected).

See also traffic calming.

Speed Camera

Speed CameraAn automated device that monitors the speed of passing traffic, usually by radar, and photographs vehicles that are exceeding the speed limit. Drivers caught in this way can be prosecuted.

See also red light camera.

Speed Limit

Every inch of public road in Britain has a speed limit — a maximum permitted legal speed for that section of road. It must be posted on signs when the limit changes. Most roads — especially those not surveyed to find a safe limit or those outside built-up areas — are subject to the National Speed Limit.

See also repeater.


SpurA short linking section of road used to connect one road with another. Any type of road can have a spur — B-roads, A-roads and motorways alike all have examples.

All spurs must have a 'parent' road which they exist to serve and which they connect to another road or place. Frequently a spur will be of a similar standard to its parent and will often assume its number, and will in almost all cases terminate on its parent rather than go across it. The M23 motorway, for example, has a spur to Gatwick Airport, which is also numbered M23. This duplication of numbers is safe since any traffic on the M23 spur will be going to or from the M23 proper.

See also number.


  1. A red octagonal road sign that indicates a particularly dangerous junction, usually because of restricted visibility for traffic emerging from a side road onto a major road. Drivers are expected to come to a full stop when they encounter one. It is used very sparingly in the UK and it is much more common to find Give Way signs.
  2. Something you should do when you encounter a red traffic light.

Suicide Lane

A single-carriageway road with three lanes. The central lane is for use by vehicles overtaking in either direction, and is used by fast moving vehicles in opposite directions, neither of which has priority over the other. The name derives from the observation that the three lanes are "left side, right side and suicide".

The suicide lane was once very common in Britain, particularly before motorways existed for most long-distance journeys. Many former trunk roads have two very wide lanes, where the road has simply been repainted from the original three lanes.

Image Feature on Abbreviations for road widths


The angle of a road's surface as it turns, with the carriageway banked to slope downwards to the inside of the corner. This assists vehicles in cornering.

See also camber and crossfall.

Symmetric Widening

A technique used to widen a road which involves adding an equal amount onto each side of the existing road surface.

See also asymmetric widening; parallel widening.



The place where a diverging or merging lane appears or disappears gradually. For a standard merge, for example, the taper is the length of road between the tip of the merge nose and where the merging lanes disappear completely.


Tiger TailingA type of traffic island painted onto the road surface to divide the lanes of a two-lane sliproad where it joins the main carriageway. It is used on sliproads carrying large volumes of traffic to space out the points where traffic merges. It is also used less regularly at busy diverges.


The simplest three-way junction possible, where one road ends on another. Named because from above, it resembles a letter T. If this excited you, just wait until you see the crossroads.


A fee charged to motorists for using a road or section of road. Traditionally in Britain these only apply to privately run toll roads, or tunnels and bridges where the excessive construction costs are repayed by the tolls. The DBFO concept (where a private company maintains a road for the government) means that 'ghost tolls' are paid by the government for every vehicle using the road. The first DBFO road to charge a fee directly to motorists using toll booths across the road is the M6 Toll near Birmingham, which opened in late 2003.


TotsoA situation where a continuous route number departs from the mainline of the road ahead. Totso is an acronym for 'Turn Off To Stay On', since this is what you have to do at one. For example, if you head up the A30 from Exeter, you have to turn right at a totso to remain on the A30, since the road ahead is the A303. The through road at the junction does not retain one number.

Toucan Crossing

Very similar to a pelican crossing, with one red pedestrian light and two green, one showing a green man and one a bicycle. Some early examples segregated pedestrians from horses and cyclists, with each having separate lights. The name Toucan is derived from the idea that 'toucan' cross at once. It's not a very good joke.

See also pegasus crossing; pelican crossing; puffin crossing; zebra crossing.


Technically this term applies to anything that uses a road to move around, though usually it refers to motorised vehicles like cars, buses and lorries.

Traffic Calming

Where obstacles such as speed bumps, chicanes, traffic islands and mini-roundabouts are placed on roads with the intention to slow down traffic — hence 'traffic calming'. Frequently these measures are applied on roads thought to be used as shortcuts or as racetracks by less responsible motorists. Often they actually provide a more exciting obstacle course for offenders, increased congestion on surrounding roads, and a decrease in public faith in these measures to do anything more than delay road users. (Yes, that's right, I don't like them.)

Traffic Jam

Any build-up of traffic. Despite the frequency with which traffic jams can be found on the roads, nobody has ever successfully tasted one to see what flavour it is.

See also congestion; queue.

Traffic Lights

Traffic LightsSets of red, amber and green lights by the side of the road used to control traffic. (I hope you knew that already.) Used in a variety of situations, from junctions to roadworks and fire stations. Sometimes called traffic signals.

See also gyratory; pelican crossing; ramp metering.

Traffic Officer

See Highways Agency Traffic Officer.

Traffic Signals

See traffic lights.

"Transport" lettering

The two types of lettering designed for use on motorways along with "Motorway Permanent". They were also adopted for use on all other types of road in the Worboys Report. There are two "Transport" alphabets: Transport Heavy and Transport Medium, designed by Jock Kinneir. They are modified versions of "Aksidenz Grotesk", adjusted to improve clarity and readability.


A type of free-flowing interchange used where one road terminates on another.

Image Feature on Trumpet junctions

Trunk Road

A road maintained at the level of national government. All other roads are the responsibility of local authorities. Trunk road status is never visible to road users — road numbers, signing, classification and primary status are all completely disconnected with trunk status. An attempt was made in Scotland to remove all non-trunk primary routes, thus making trunk routes and primary routes the same, but it failed and the two remain unrelated.

See also detrunk.


The Traffic Signs Regulations and General Directions, a document published by the Department for Transport which sets out the correct standards for traffic signs in the UK. It is periodically updated with new designs. Signs that do not conform to TSRGD are an unlawful obstruction to the highway. It is one of the few acronyms on this page that is only rarely written or spoken in full, which is why it appears here in its abbreviated form.



A road which has no number. Numbered roads are referred to as classified, therefore a road with no number is unclassified. Most unclassified roads are actually given numbers by the highway authorities responsible for maintaining them, but these numbers are only for internal use and should not appear on road signs.

See also C-Road.


UnderpassThe opposite of a flyover — a bridge carrying a road under another road. In many ways it's a flyover seen from the other point of view.

See also overbridge and overpass.


An improvement to a road, almost always referring to a physical improvement such as widening the carriageway or rebuilding a junction. It might also refer to promoting the road to a more important number.

See also downgrade.

Urban Motorway

Just like a regular motorway, except it's built in an urban environment which means it is subject to lower design standards, often with closely spaced exits and entries, narrow lanes, tight corners and, frequently, no hard shoulder.

Useless Multiplex

Or, if you like, "Useless" Multiplex. A specific type of multiplex where the signposted (dominant) route in the multiplex terminates during the length of the multiplex instead of splitting off again and going its own way. Ironically, this is only done where it's useful for navigation: see the A30/A303 multiplex, where the A303 ends rather than diverge from the A30 again. This is because it terminates on the M3, which makes more sense to motorists than a short section of A30 linking M3 to A303.



Part of a road numbering system specific to the new town of Milton Keynes. The V stands for Vertical and designates a road that runs north to south. V-roads all have names that end in "Street" and are numbered from V1 in the west to V11 in the east. The V-roads and their H counterparts are marked on relevant roadsigns, particularly where they intersect.

See also H-Road.

Variable Message Sign (VMS)

A sign which is capable of changing to display a number of messages. These can be in the form of a matrix sign or a panel which can rotate to expose several different sides displaying different messages. The latter type is common on car park direction signs in city centres, with panels which are remote-controlled to rotate, displaying "Space", "Nearly Full" or "Full".

Variable Speed Limit (VSL)

vslA motorway speed limit that can be changed to suit traffic conditions, controlled by electronic matrix signs and legally enforceable. It is successfully used to reduce congestion by reducing the gaps between vehicles and thus increasing throughput.

See also Active Traffic Management; controlled motorway.


The space along the side of the carriageway, when no footpath is present — usually grass but sometimes paved.


Weaving Section

Found on the main carriageway of a road between points where a new lane joins from a sliproad and exits again at another sliproad shortly after. The weaving section is the space between the entry and exit where traffic quickly weaves between lanes.


In the early 1960s a government committee produced a document known as the Worboys Report (after the head of the committee) which made recommendations for a new scheme of road signing. The scheme, which is still in use today, has become known as Worboys signing.

Image Feature on Worboys signs



See crossroads.



The American equivalent to Give Way. This term also seems to have appeared on a handful of very early Give Way signs.


Zebra Crossing

Zebra CrossingA pedestrian crossing which relies on road traffic giving priority to pedestrians when one is waiting to cross. They are named for the zebra-like black and white stripes painted across the carriageway. An integral feature of British zebra crossings are Belisha Beacons.

Image Feature on Zebra Crossings

See also pegasus crossing; pelican crossing; puffin crossing; toucan crossing.


The name usually used to refer to the nine areas of mainland Britain that are used to allocate road numbers. The zones are divided by A-roads with single digit numbers. Sometimes also called cones because most are triangular (sort of, if you use your imagination).

Image Feature on Road Numbers

With thanks to...

In no particular order — Jeff Wagstaff, Mike Wilkinson, Paul Evans, Clive Harmson, Ted Pottage, Kevan Fleckney, Michael Elliott, John Rowland, Doug Farnan, Keith Jones, Peter Hadrys, Mark Ellerington, Paul Everitt, Brian Davies, James, Robert, Toby Speight, Dave, David Summers, Pete Harman, Ash, Paul Gowen, Martin Vlietstra, Alan Whittingham, Steven Jukes, Jack Robinson, Andy Emmerson, Guy Barry, Simon M4Man, Chris 'Awkward' McKenna, David D Miller, Peter Edwardson, and Simon Mold, all of whom have stopped this page being as inaccurate as it used to be.