Climbing lanes or crawler lanes are a roadway

lane In road transport, a lane is part of a roadway that is designated to be used by a single line of vehicles to control and guide drivers and reduce traffic conflicts. Most public roads (highways) have at least two lanes, one for traffic in each ...

design. They allow slower travel for large vehicles, such as large trucks or

semi-trailer truck A semi-trailer truck, also known as a semitruck, (or semi, eighteen-wheeler, big rig, tractor-trailer or, by synecdoche, a semitrailer) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-traile ...

s, ascending a steep

grade Grade most commonly refers to: * Grade (education), a measurement of a student's performance * Grade, the number of the year a student has reached in a given educational stage * Grade (slope), the steepness of a slope Grade or grading may also ref ...

. Since climbing uphill is difficult for these vehicles, they can travel in the climbing lane without slowing traffic.

Description

Climbing lanes are a roadway

design, typically used on major routes such as

motorway A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway and expressway. Other similar terms i ...

s and

interstate highway The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, is a network of controlled-access highways that forms part of the National Highway System in the United States. Th ...

s. In the UK, the climbing lane is also referred to as a crawler lane. They allow slower travel for large vehicles, such as large trucks or

s, ascending a steep

. Since climbing uphill is difficult for these vehicles, they can travel in the climbing lane without slowing traffic.

Variants

A variation that has become common with newer roads and more recent widening schemes is to add an additional "fast" ( passing) lane for the stretch which otherwise would have had a crawler lane. This allows underpowered vehicles to remain in the existing "slow" lane without having to purposely pull left into the "slow" lane which drivers may not want to do because they then have to try to merge back into faster traffic (possibly still at low speed) when it ends. Instead, the more normal requirement to purposely pull out to pass slower vehicles, and back in after doing so or when the lane ends, generally with a smaller speed differential (as they will be rejoining what is already a passing lane), is placed on faster drivers.

Safety

On normally 2-lane roads without a divider, the climbing lane effectively creates a bi-directional central passing lane of the original uphill running lane. Its subsequent risk of head-on

collisions In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great f ...

, they are sometimes referred to as "suicide lanes". In some cases to reduce the risk, the road will be signed to prohibit

overtaking Overtaking or passing is the act of one vehicle going past another slower moving vehicle, travelling in the same direction, on a road. The lane used for overtaking another vehicle is often a passing lane farther from the road shoulder which i ...

when going downhill. Variations on this theme include altered road markings to highlight the climbing lane as being a temporary addition to the normal two (shorter dashed lines similar to those on merge/diverge lanes), or more clearly demarcating the two higher speed lanes (e.g. with markings that prevent uphill fast traffic using the downhill lane to pass slightly slower uphill vehicles themselves passing "crawlers", but still allowing downhill vehicles to overtake using the faster uphill lane if necessary, which has the effect of creating a false "center" line between the two regular lanes). In the UK the additional climbing lane and the single downhill lane are generally separated by double white solid lines. It is an offence to position any part of your vehicle to the right of a double white line punishable by 3 penalty points, therefore this marking in itself prohibits any use of the climbing lane for overtaking by vehicles travelling downhill. As

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construction ...

s and

recreational vehicle A recreational vehicle, often abbreviated as RV, is a motor vehicle or trailer that includes living quarters designed for accommodation. Types of RVs include motorhomes, campervans, coaches, caravans (also known as travel trailers and camper ...

s must use

low gear A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission ...

to descend slowly, an additional lane may also be built on the downhill side. This prevents the vehicles from overusing their

brake A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...

s, which may overheat and cause a runaway vehicle.

References

{{Road Road infrastructure

Description

Variants

Safety

See also

References