A motorway (United Kingdom, Republic of Ireland, and some Commonwealth nations) is both a type of road and a classification. Motorways may also be regarded as highways, designed to carry a large volume of traffic where a normal road would not suffice or would be unsafe, usually between cities. In the UK they are predominately dual carriageway, usually with two lanes in each direction and grade-separated access.
Many roads in the UK and the Republic of Ireland are of near-motorway quality, but are not classified as such (generally for breaking the above rules). These are referred to as dual-carriageways, which may be subject to a lower speed limit.
In both countries, motorways are denoted by blue signage (and an M-prefixed road number). Speed limits are generally higher than on ordinary roads, with an overall limit of 70 mph (113 km/h) for cars in both the UK and the Republic. Some types of vehicle may be subject to a lower limit, while often sections of motorway are subject to lower speed limits due to local driving conditions. Lanes closest to the edge of the road (inside lanes) are intended for general driving, while the outer lanes are intended for overtaking (passing) slower moving vehicles.
Roads in the Republic of Ireland will however, have metric speed limits imposed in late 2004/early 2005 to conform to both European convention and existing directional signage (metric since 1970s). It is likely that the speed limit for motorways in Ireland will then be slightly increased to 120 km/h (75 mph).
Unlike in some other countries, drivers are not permitted to pass on the inside unless traffic in the 'faster' lanes is stationary. With a touch of black humour, the practice is popularly known as undertaking. Learner driverss, pedestrians, cyclists and underpowered vehicles (e.g. small scooters) are generally banned from motorways and a 'minimum speed limit' may apply.
The road surface is generally asphalt ('black top') or concrete ('white top'). White dashed lines denote the lane separation, while an unbroken white line is painted alongside the median. A white line (or in the Republic of Ireland, a dashed yellow line) on the edge of the slow lane marks the edge of the hard shoulder. The hard-shoulder is not used for traffic and is reserved for breakdowns or emergency manoeuvres.
Other features are crash-barriers, cat's eyess and increasingly, textured road markings (similar concept to rumble-strips). In the UK it is a requirement that all motorways have emergencytelephones at regular (usually one mile) intervals which connect directly to the police.
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 on either 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. An Irish invention is the signal-controlled roundabout which is often used in these situations. A further degree of complexity is present in Britain with varying types of Spaghetti Junction style interchanges.
In Britain there are plans to upgrade many motorways as well as upgrade some roads to motorway status. In the Republic of 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.
The newest UK motorway to open was the M6 Toll bypassing Birmingham in 2004, which is also the only section of toll motorway in England.
A motorway (