Motorway
A motorway (in the United Kingdom, Ireland, New Zealand and some Commonwealth
nations) is both a type of road and a classification. Motorways are 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.
Equivalent terms in other countries include autoroute, Autobahn, freeway,
autostrada, autopista, motorvej, motorväg and autoput.
Regulations
A Sunday in April 2004 at 5 pm local time on Britain's busy M25For a road
to be classified as motorway a number of conditions must be fulfilled.
The following conditions generally apply:
Motorways must be accessed at junctions by slip roads off the sides of
the main carriageway;
Separate motorways are 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 not permitted (except at toll booths and certain small
interchanges);
The start and end of a motorway must have signposted entry and exit points;
Certain types of transport are banned, typically pedestrians, bicycles,
learner drivers, horses, agricultural vehicles, underpowered vehicles
(e.g. small scooters, invalid carriages).
In the UK and the Republic of Ireland there are further restrictions:
The central reservation must remain unbroken (an exception being the
Aston Expressway in Birmingham, which has none);
Emergency phones must be provided at a regular distance;
A 'minimum speed limit' may apply.
Note that these only apply to roads directly designated as motorways.
Roads may also be indirectly designated as such, see #Inheritance below.
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.
Many roads are of near-motorway quality, but are not classified as such
(generally for breaking one or more of the above rules). These are referred
to as dual carriageways, which in Britain usually have the same 70 mph
(110 km/h) limit (the limit in Ireland and New Zealand is the regular
100 km/h (65 mph) limit). They may be subject to a lower speed limit (e.g.
in urban areas).
Queues after an accident on Britain's M4In Ireland and the UK, motorways
are denoted by blue signage and an M-prefixed or suffixed road number.
Speed limits are generally higher than on ordinary roads, with an overall
limit of 70 mph (110 km/h) for cars in the UK. 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 are intended for general driving – these are
hence the "inside" lanes, while the lanes closest to the median
are intended for overtaking (passing) slower-moving vehicles – hence
they are termed "outside" lanes. Some vehicles, notably heavy
goods vehicles, are not permitted to use the rightmost lane on a three
(or more) lane motorway.
Roads in the Republic of Ireland have had metric speed limits since 20
January 2005 to conform to European convention and to existing directional
signage, which has long shown metric distances. The new speed limit introduced
for motorways is 120 km/h (75 mph).
In New Zealand motorways were historically distinguished from other roads
with green signage. This changed with the establishment of Transit New
Zealand which extended the use of green signs to the entire state highway
network. The speed limit on motorways is fixed at the top limit for state
highways, 100 km/h (65 mph). This rule is most in evidence in Wellington
where Centennial Highway in the Ngauranga Gorge is not designated as a
motorway because of the steep gradient, general usage and slow-speed junctions,
despite leading directly into the Johnsonville-Porirua motorway.
The Conservative Party had proposed increasing the UK motorway speed limit
to 80 mph (130 km/h), should they gained power at the past election. Many
road safety groups feel this would be a good idea, as it more closely
represents the normal (and, they claim, safe) driving practice of the
majority of motorway users.
As in Germany but unlike in some other countries, drivers are not permitted
to pass on an inside lane (a lane further from the median) unless traffic
in the 'faster' lanes is stationary. With a touch of black humour, the
practice is popularly known as undertaking.
Features
Diagram showing lanes and road layout, with Irish road markings.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.
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.
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.
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.
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.
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'.
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.
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