Motorway

A motorway (in the United Kingdom, Ireland, New Zealand 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 predominantly dual-carriageway roads, usually with three lanes in each direction although four-lane and two-lane carriageways are also common, and all have grade-separated access.

Features

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 (usually known as the 'central reservation'). A white line (or in the Republic of Ireland, a 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. Generally lanes closer to the centre of the road (outer lanes) are used for overtaking, while lanes near the edge of the road (inner lanes) are used for slower traffic (see diagram on right), as in the UK it is illegal to overtake on the left (commonly known as undertaking) except in emergencies, when signs indicate drivers may do so or when traffic is moving slowly.

Related Topics:
Asphalt - Concrete - Hard shoulder - Outer lane

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Traffic should always use the lefthandmost lane possible. Generally this means a vehicle should use the lefthand lane next to the hard shoulder, and use the other two lanes only for overtaking manouvers, moving back into the left lane once they have passed the slower vehicle(s). In heavy traffic, it is acceptable to cruise in the middle lane to pass slower vehicles to avoid constant lane changes.

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A significant problem on motorways is the 'middle lane hog', a driver who drives in the middle lane when there is no reason to do so. This can be very frustrating for other drivers. Faster vehicles approaching in the left hand lane have to manouver across four lanes of the motorway rather than two to pass such a vehicle, since undertaking is forbidden. Drivers of heavy goods vehicles can be especially frustrated by a middle lane hog, as their vehicles are not permitted to use the righthandmost lane under normal circumstances. Since undertaking is forbidden, a heavy goods vehicle cannot legally pass a slower moving vehicle in the centre lane at all.

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In the UK lanes in a given direction are numbered from left to right as lane 1, lane 2, lane 3, etc. Lane 1 is the lane next to the hard shoulder.

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Other features are crash barriers, cat's eyes and increasingly, textured road markings (a similar concept to rumble-strips). In the UK it is a requirement that all motorways have emergency telephones at regular (usually one-mile) intervals which connect directly to the police.

Related Topics:
Crash barrier - Cat's eye - Rumble-strip - Emergency - Telephones - Police

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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. 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'.

Related Topics:
Flyover - Roundabout

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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.

Related Topics:
Signal-controlled roundabout - Spaghetti Junction

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