<P> Driving in the United Kingdom is governed by various legal powers and in some cases is subject to the passing of a driving test . The government produces a Highway Code that details the requirements for all road users, including drivers . Unlike most countries in the world, UK traffic drives on the left . </P> <P> British roads are limited for most vehicles by the National Speed Limit . Road signs in the UK use imperial units, so speed limits are posted in miles per hour . Speed limits are the maximum speed at which certain drivers may legally drive on a road rather than a defined appropriate speed, and in some cases the nature of a road may dictate that one should drive significantly more slowly than the speed limit may allow . This restricts some vehicles by default to a speed of 30 mph in built up areas, and some light vehicles to 60 mph on single carriageways and 70 mph on dual carriageways and motorways, with some large vehicles or some of those towing trailers subject to reduced limits on some roads depending on the class of both road and vehicle . Sections of road subject to the national or in - town speed limit only require limit marker signs at the start of a section, without repeaters, provided street lights are or are not present as appropriate . Speed limits of 5 mph, 20 mph, 30 mph, 40 mph, 50 mph and 60 mph are also used on roads in the UK where it is deemed that the national or in - town speed limit is inappropriate, with repeater signs posted at regular intervals . </P> <P> Drivers on dual carriageways (which may or may not be motorways) are usually expected to use the left-most lane unless overtaking other vehicles on the road, unless signs or road markings indicate that the left-most lane (s) is only for traffic leaving at the next junction . Drivers who wish to overtake a slower vehicle are thus expected to move out from their lane (having used the indicator lights to warn other road - users of their intention to do so), pass the slower vehicle and return to the left-most lane . This enables faster traffic to overtake unhindered if it wishes to do so . On the UK's busiest roads, where there may be four or more lanes in each direction, there is often a situation where overtaking becomes continual as each successive lane moves at a slightly faster speed than that to its left . </P> <P> On motorways an extra left lane termed the' hard shoulder' is usually present for use only when a vehicle has broken down . It is illegal to drive in this lane unless indicated otherwise, for example on one of the increasing number of Smart Motorways . </P>

Which lane is the fast lane in the uk
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