Motorway



This article has a km/h to mph speed conversion table; speed limits are therefore quoted only in the units of measure of the country concerned.

A motorway is a dual-carriageway limited access highway with grade separated junctions designed and built solely for motorised traffic. In English-speaking countries the term is used in the United Kingdom, some parts of Australia, New Zealand, Pakistan, some other Commonwealth nations, and Ireland in Irish). In Ireland, a road built to motorway standard, but without the designation (and the regulations and traffic restrictions resulting from that designation), is known as a high-quality dual carriageway. Motorways are identical to freeways as a road type, and comparable to the United States's Interstate Highways as a classification.

OECD Definition
The OECD has defined a motorway as:
 * French Equivalent: Autoroute.
 * Definition:
 * Road, specially designed and built for motor traffic, which does not serve properties bordering on it, and which:


 * (a) is provided, except at special points or temporarily, with separate carriageways for the two directions of traffic, separated from each other, either by a dividing strip not intended for traffic, or exceptionally by other means;


 * ''(b) does not cross at level with any road, railway or tramway track, or footpath;


 * (c) is specially sign-posted as a motorway and is reserved for specific categories of road motor vehicles.


 * Entry and exit lanes of motorways are included irrespectively of the location of the sign-posts. Urban motorways are also included.

Regulations and features
In Ireland, Hungary, parts of Australia and the UK, motorways are denoted by an 'M', prefixed (e.g. M1) or suffixed (e.g. A1(M)) road number and blue signage, distinguishing them from A&#8209;roads or N&#8209;roads, which are signed in green. This is at odds with some countries elsewhere in Europe, where the colours are reversed. In New Zealand, motorways are distinguished from regular state highways with the word 'Motorway' on entrance signage. New Zealand's motorways had green road signs while everywhere else had black, until green signs were spread to the entire State Highway network (the national highways) by Transit New Zealand.

The construction and surfacing of motorways is generally of a higher standard than conventional roads, and maintenance is carried out more frequently; in particular, motorways drain water very quickly to reduce hydroplaning/aquaplaning. The road surface is generally asphalt concrete (popularly referred to as tarmac) or portland cement concrete. Other features are crash barriers, cat's eyes and, increasingly, textured road markings (a similar concept to rumble-strips).

Common criteria
For a road to be classified as motorway the OECD conditions described above must apply. The implications of these conditions include:
 * Accessed at junctions by slip roads off the sides of the main carriageway or joined by link-roads at an interchange, the object of which is to allow traffic to change route without stopping or slowing significantly;
 * Traffic lights are seldom necessary except at toll booths and to control the number of vehicles entering the motorway from the slip road during busy periods) - see ramp meter;
 * Certain types of transport are banned, typically pedestrians, bicycles, learner drivers, horses, agricultural vehicles, underpowered vehicles (e.g. small scooters, invalid carriages). In the Republic of Ireland, the "Motorway Ahead" sign at every motorway junction lists the excluded classes of vehicles (this sign was also formerly used in the United Kingdom - on which the Irish version is based - but has been almost entirely phased out). In the UK, at the last junction before a road becomes a motorway, a sign is posted, reading for "prohibited traffic". In most Australian states, a sign for "Motorway Entrance" or "Freeway Entrance" was put at the start of these roads, but these too are being phased out. In New Zealand, a no pedestrians and no motorcycles and no bicycles sign precedes the "Motorway Begins" sign.



In the UK and in Ireland there are further restrictions:
 * The central reservation with a continuous crash barrier (an exception being the Aston Expressway in Birmingham, which has an empty lane instead and a section of the M40 in Warwickshire, with an unusually wide grassy median strip separating the carriageways). Beginning in January 2005, and based primarily on safety grounds, the UK's Highways Agency's policy is that all new motorway schemes are to use high containment concrete step barriers in the central reserve. All existing motorways will introduce concrete barriers into the central reserve as part of ongoing upgrades and through replacement as and when these systems have reached the end of their useful life. This change-of-policy applies only to barriers in the central reserve of high speed roads and not to verge side barriers. Other routes will continue to use steel barriers. The Republic of Ireland has similarly introduced concrete barriers instead of its former policy of wide grass medians (the UK and Ireland share the same Design Manual for Roads and Bridges).
 * Emergency telephones (which connect directly to the police, except in England where they connect you directly to the nearest Highways Agency Regional Control Centre who will send either their own officers (HATO's) or other emergency services as required) are provided at a regular intervals (in the UK emergency telephones are situated at intervals of 1 mile, and at 2 km in Ireland)
 * no roundabouts apart from at the start and finish (some exceptions)
 * Hard shoulder available most of the time
 * Other roads are connected at motorway interchanges only. No roads join at any other point except for maintenance access.
 * Most junctions are numbered

''Note that these only apply to roads directly designated as motorways. Roads may also be indirectly designated as such, see Inheritance below.''

Traffic on a motorway is required to keep moving, except in exceptional circumstances (cases where traffic queues have built up, the vehicle has broken down, or the driver has been instructed to stop by a police officer). A minimum speed limit of 50 km/h applies in the Republic of Ireland.

A motorway in England and Wales, whether by design or inheritance, must have a Statutory Instrument (SI) defining a stretch of road and sliproads as a special road under the Highways Act 1980 (other legislation governs motorways with broadly similar effect in Scotland and Northern Ireland). In the Republic of Ireland, a Motorway Scheme must be made under the Roads Act 1993 prior to the road's construction. Alternatively, a Statutory Instrument defining the stretch of road as a motorway may also be made under the Roads Act 2007, however this process may only be used for high-quality dual carriageways either open, in planning, or under construction on the day the Act was signed into law.

Speed limits
Motorway safety is significantly higher than that of other roads, and the speed limits correspondingly higher, although some types of vehicle, such as heavy goods vehicles, may be subject to lower limits.

In the United Kingdom the speed limit for cars and motorcycles on motorways and dual-carriageways is 70 mph unless a lower limit is displayed. Many HGVs are restricted to 90 km/h (displayed as 56 mph). British motorways originally had no speed limit, and were designed for traffic travelling up to 100 mph. Although the design speed of 100 mph remains, all British motorways and dual carriageways are now subject to the national speed limit of 70 mph for motorcars and motorcycles. Some may have lower limits for various local reasons. A Department for Transport (DfT) study at several sites in 2006 showed that over half of all motorway traffic was travelling in excess of this limit. In 2004 the Conservative Party proposed increasing the motorway speed limit to 80 mph on some stretches, although this did not appear in their 2005 election manifesto. The Association of British Drivers supported the proposal, as they claimed it more closely represents the normal (and, they claim, safe) driving practice of the majority of motorway users.

In Ireland the speed limit for motorways and some dual-carriageways is 120 km/h. In certain sections of motorway the speed limit is 100 km/h, however the vast majority of the network is 120 km/h.

Lanes
Most motorway carriageways comprise a main running surface, with a hard shoulder along one edge, and a median or central reservation separating it from the other carriageway along the other edge. The hard shoulder is generally provided for use in emergencies, such as breakdowns, only. However the M42 in the UK has a system whereby a small section of the hard shoulder can be used as an extra lane during busy periods.

The nearside edge (the edge up against the hard shoulder) of the running surface is marked with a solid white line, or in Ireland, a solid yellow line. The offside edge of the running surface (the edge nearest to the median) is marked with a solid white line. The running surface is divided into lanes by white dashed lines. On the M42 in the UK, the hard shoulder line is not textured because it is frequently used as a running lane.

In the United Kingdom and in Ireland the lanes in a given direction are numbered sequentially from the nearside (hard shoulder), such as lane 1, lane 2, lane 3, etc.

The lane closest to the hard shoulder is generally intended for normal steady driving, while the other lane or lanes, those closer to the median, are intended for overtaking or passing slower-moving vehicles. Vehicles are expected to use the nearside-most lane that is clear. The British Highway Code states that vehicles must pass on the right, unless in heavy traffic or when the vehicle is turning left. Similar rules apply on German autobahns and in some other countries. In heavy traffic, it might be acceptable to cruise in any lane, and to pass slower vehicles on either side, to avoid continual lane changes.

Junctions
The most basic motorway junction is a two-lane flyover with four slip-roads, two on each side of the motorway, to exit or enter. A simple crossroads or roundabout is present at each end of the flyover. A rather large version of a roundabout, using two curved flyovers, is sometimes used to present a single large junction for users of the slip-roads or crossing road. The slip roads leading off the motorway are known as 'exit sliproads', those leading onto the motorway as 'entry sliproads'. The precise sliproad at any junction may be identified by reference to the direction of the carriageway, for example 'northbound entry slip'.

The signal-controlled roundabout is often used in these situations and has become very common in Ireland. A far greater degree of complexity is present in Britain, with varying types of Spaghetti Junction-style interchanges.The M50 Western Parkway in Dublin is going through a major upgrade with spaghetti style junctions being introduced to relieve traffic congestion.

Motorway junctions are usually given a number, indicated in the UK and in Ireland with a white number on a black background in the corner of signs approaching that junction. The same junction number is used in both directions on the motorway. Sometimes, where a junction is newly inserted between two existent junctions, it will be given a letter also (e.g. 2A). In Ireland, the junction numbering has only been used consistently on the M50 since it was opened, however a junction numbering scheme is now being applied to all motorways. This has necessitated certain junctions being renumbered on the M7 (and, in future, on the M4). In Auckland, New Zealand, exit numbers are distance-based, and are indicated by a green sign reading "Exit XXX" (e.g. Exit 441) on top of exit signage.

In Ireland, when two motorways meet, it is often the end point/start point of one of the motorways. The motorway that is ending usually blends into the other at a restricted junction, permitting traffic to exit and enter the motorway from one direction only. Examples of this are the M4/M6 junction, the M7/M9 junction, and the under-construction M8/M7 junction. These junctions can cause frustration for road users, who must travel to the next available junction and then change direction to use the restricted exit.

Location and construction
Major intercity or national routes are often built or upgraded to motorway standard. Motorways are also commonly used for ring roads around cities or bypasses of built-up areas. In New Zealand, motorways tend to only occur in large cities, for purposes of taking commuters between the suburbs and the central city.

In Britain there are plans to improve many motorways as well as to upgrade some roads to motorway status. In Ireland, the National Roads Authority has been connecting main cities with motorways as part of a six-year National Development Plan. The European Union has part-funded many motorway projects in the past, as part of a Trans-European Transport Networks, and there are plans to invest billions of euro in such projects in the next ten years, though this could be postponed due to the economic climate.

One of the most recently constructed motorways in the UK is the M6 Toll, bypassing Birmingham and Wolverhampton, which opened in December 2003 and is the only completely toll motorway in England. There are tolled sections of motorway on the M4 and M48, where they cross the River Severn at the Severn crossings. Although the crossing of the River Thames east of London on the M25 is tolled, the bridge and tunnels themselves are officially designated the A282 to permit usage by non-motorway traffic. In Ireland, the M1, M4, M8 and M50 all have tolled sections (the M50 toll being the only free flow toll in Ireland), and under construction sections of the M3, M6 and M7 also due to have tolls.

Intermediate forms
While a motorway is being built or upgraded, it may exist in an intermediate form sometimes referred to as semi-highway, half-motorway or semi-motorway that lacks all the characteristics of a finished motorway. Such a road is often a grade-separated, controlled-access undivided highway that constitutes a single carriageway of a future full-profile highway while the second one is built. While physically similar to two-lane freeways, these roads are strictly built as temporary structures as a part of a freeway or highway in construction.

Semi-highways can sometimes remain in the same state for long periods of time because of the high cost of building on certain terrain, such as in some parts of Switzerland. Sections of semi-highways are also frequently found in difficult terrain (where construction costs may be prohibitive), as a temporary and lower cost alternative to full construction. For example, instead of using two tunnel boring machines, one machine can excavate both without delaying the opening of the highway in either direction.

Most older motorways in Croatia were originally built in phases where the intermediate form existed, the most prominent example being the A6 motorway, large sections of which remained in this state between 2004 and 2008. The Croatian Roads Authority announced that in the five years ending in 2005 of highways were built and an estimated  were being planned. In this same time frame of semi-highways were completed, with  being planned.

Several sections of German Autobahnen have yet to be upgraded to full profile. The lower 100 km/h speed limit for undivided roads applies in derestricted speed zones, and passing may be permitted in the oncoming traffic lane. Examples include BAB 60 near the Belgian border and BAB 62 between Landstuhl and Pirmasens in Rhineland-Palatinate. In contrast, German federal highways (Bundesstraßen) are usually built as permanently undivided highways with frequent grade separations.

Newer Hungarian motorways are also built first as semi-highways and later completed. Examples are the M2 and M15. The M2 also features an unusual three-lane configuration. The M9 highway section connecting Szekszárd-Dombóvár in Transdanubia, Hungary will utilise 3 semi-highway sections during the construction process before achieving speedway status. Highway 66-611 will be modernized requiring a section to initially start with the construction of a two-lane semi-highway. The aim is to increase road security reducing collisions and achieve status similar to the M65 highway.

Swiss Autobahns are also sometimes built short of their design for topographical and financial reasons. The trans-Alpine A13 includes many tunnels and sections of semi-highway. These are similar to the Autostrassen, which are typically permanent structures.

Many toll roads in autopistas in Mexico are built in this way, often through difficult terrain.

The Pan-European Corridor X in Serbia will utilise semi-highways until full funding and construction can be completed. 800 million euros is the initial investment for construction of Corridor X, however it is estimated that another 1.6 billion euros will be needed for the entire length of construction. At this initial stage it is projected that about of Corridor X through Serbia will be finished highway, and the remainder of the route will be semi-highway or local main roads.

Inheritance
In the United Kingdom and in Ireland, certain types of traffic are not permitted on motorways. Thus, to avoid having people being forced to travel illegally, there are a number of rules about stretches of road that must be designated as motorways.

In all cases, there must be an escape route for traffic not wishing or not permitted to enter the motorway. As a result, the motorway technically begins as soon as the escape route has diverged from it. For example, at a grade-separated junction, the motorway starts at the junction with the exiting slip road, and the opposite slip road is also part of the motorway for this and the following reason. An exception was the A1(M) near Leeds, which was "illegal", since pedestrians could legally cross 300 yards beyond the start of the motorway, but then cyclists and other types of traffic not permitted on motorways had no way of turning back - the escape route was the "Boot and Shoe" one mile before. This is remedied by the A1(M) extension.

As a result, this creates a less-restrictive set of rules for the standard of the road. Roads whose only destination is a motorway must be assigned motorway status, notwithstanding the possibility of their not being built to normal motorway standards. For example, the A48(M) motorway outside Cardiff begins after the last exit to St Mellons, since by staying on the dual carriageway you cannot get anywhere other than the M4 eastbound; however, it is a motorway-grade highway.

Great Britain
In England and Wales, the numbers of major motorways followed a numbering system separate to that of the A-road network, though based on the same principle of zones. Running clockwise from the M1 the zones were defined for Zones 1 to 4 based on the proposed M2, M3 and M4 motorways. The M5 and M6 numbers were reserved for the other two planned long distance motorways. The Preston Bypass, the UK's first motorway, should have been numbered A6(M) under the scheme decided upon, but it was decided to keep the number M6 as had already been applied. Certain portions or bypasses of A-roads may be designated as motorways, the name of these portions being given the suffix "(M)". An example is the A1(M).

In Scotland, where the Scottish Office rather than the Ministry of Transport and Civil Aviation had the decision, there is no zonal pattern, but rather the A-road rule is strictly enforced. It was decided to reserve the numbers 7, 8 and 9 for Scotland. The M8 follows the route of the A8, and the M80 became part of the M90 when the A90 was re-routed along the path of the A85.

Northern Ireland


In Northern Ireland a distinct numbering system is used, which is separate from the rest of Ireland and from Britain, though the classification of roads along the lines of A, B, and C is universal throughout the UK and the Isle of Man. According to a written answer to a parliamentary question to the Northern Ireland Minister for Regional Development, there is no known reason as to how Northern Ireland's road numbering system was devised. However motorways, as in the rest of the UK and Ireland, are numbered M, with the two major motorways coming from Belfast being numbered M1 and M2. The M12 is a short spur of the M1 with the M22 being a short continuation (originally intended to be a spur) of the M2. There are two other motorways, the short M3 and a motorway section of the A8 road, known as the A8(M) (similar to how motorway sections of A-roads in Great Britain are numbered).

Republic of Ireland
In the Republic of Ireland, motorway and national road numbering is quite different to the UK convention. Since the passage of the Roads Act 1993, all motorways are part of, or form, national primary roads. These routes are numbered in series, (usually, radiating anti-clockwise from Dublin, starting with the N1/M1) using numbers from 1 to 33 (and, separately from the series, 50). Motorways use the number of the route of which they form part, with an M prefix rather than N for national road (or in theory, rather than R for regional road). In most cases, the motorway has been built as a bypass of a road previously forming the national road (e.g. the M7 bypassing roads previously forming the N7) - the bypassed roads are reclassified as regional roads, although updated signposting may not be provided for some time, and adherence to signage colour conventions is lax (regional roads have black-on-white directional signage, national routes use white-on-green).

Under the previous legislation, the Local Government (Roads and Motorways) Act 1974, motorways theoretically existed independently to national roads, however the short sections of motorway opened during this act, except for the M50, always took their number from the national road that they were bypassing. The older road was not downgraded at this point (indeed, regional roads were not legislated for at this stage). Older signage at certain junctions on the M7 and M11 can be seen reflecting this earlier scheme, where for example N11 and M11 can be seen coexisting.

The M50, an entirely new national road, is an exception to the normal inheritance process, as it does not replace a road previously carrying an N number. The M50 was nevertheless legislated in 1994 as the N50 route (it only had a short section of non-motorway section form the Junction 11 Tallaght to Junction 12 Firhouse until its extension as the Southern Cross Motorway). The M50s designation was chosen as a recognisable number. As of 2008 the N34 is the next unused national primary road designation. In theory, a motorway in Ireland could form part of a regional road.

Environmental effects

 * Roadway noise: Motorways generate more roadway noise than arterial streets because of the higher operating speeds. Therefore, noise health effects are expected from motorway systems. Noise mitigation strategies exist to reduce sound levels at nearby sensitive receptors. The idea that motorway design could be influenced by acoustical engineering considerations first arose about 1973
 * Air quality issues: Motorways may contribute fewer emissions than arterials carrying the same vehicle volumes. This is because high, constant-speed operation creates an emissions reduction compared to vehicular flows with stops and starts. However, concentrations of air pollutants near motorways may be higher because of the substantial traffic volumes. Therefore, the risk of exposure to elevated levels of air pollutants from a motorway may be considerable, and further magnified when motorways have traffic congestion.

Great Britain
A map 'Shewing Future Pattern of Principal National Routes' was issued by the Ministry of War Transport in 1946 shortly before the law that allowed roads to be restricted to specified classes of vehicle (the Special Roads Act 1949) was passed. The first section of motorway, the M6 Preston Bypass, opened in 1958 followed by the first major section of motorway (the M1 between Crick and Berrygrove), which opened in 1959. From then onwards, motorways opened on a regular basis right into the 1980s; by 1972 the first 1000 mi of motorway had been built. Whilst roads outside of urban areas continued to be built throughout the 1970s, opposition to urban routes became more pronounced. Most notably, plans by the Greater London Council for a series of ringways were cancelled following extensive road protests and a rise in costs. The completed M25 London Orbital opened in 1986. In 1996 the total length of motorways reached 2000 mi.

Ireland
Legal authority existed in the Special Roads Act (Northern Ireland) 1963 similar to that in the 1949 Act. The first motorway to open was the M1 motorway, though it did so under temporary powers until the Special Roads Act had been passed. Work on the motorways continued until the 1970s when the oil crisis and The Troubles both intervened causing the abandonment of many schemes.

In the Republic of Ireland the Local Government (Roads and Motorways) Act 1974 made motorways possible, although the first section, the M7 Naas Bypass, did not open until 1983. The first section of the M50 opened in 1990, a part of which was Ireland's first toll motorway, the West-Link. However it would be the 1990s before substantial sections of motorway were opened in Ireland, with the first completed motorway – the 83 km (52 mi) M1 motorway – being finished in 2005.

Under the Transport 21 infrastructural plan, motorways or high quality dual carriageways are being built between Dublin and the major cities of Cork, Galway, Limerick and Waterford by the end of 2010. Other shorter sections of motorway either have been or will be built on some other main routes. In 2007 legislation (the Roads Bill 2007) was proposed to allow existing roads be designated motorways by order. Legislation only allows for new build roads to be designated motorways. It is now intended that all the HQDCs on the major inter-urbans – other than some sections near Dublin on the N4 and N7, which do not fully meet motorway standards - will be reclassified as motorway. The first stage in this process occurred when all the HQDC schemes open or under construction on the N7 and N8, and between Kinnegad and Athlone on the N6 and Kilcullen and south of Carlow on the N9, were reclassified motorway on 24 September 2008. Further sections of dual carriageway are proposed to be reclassified as motorway.