Slip lane

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In road design, a slip lane, also known as a filter lane in the United Kingdom, is a road at a junction that allows motorists to change roads without actually entering an intersection.[1]

Illustration (left-hand traffic): the blue vehicle in the slip lane must give way to the green and red vehicles even though the latter is at a give way control.

Some intersections that are controlled by lights offer a slip lane, which allows cars to bypass the lights when they turn. That helps ease congestion and improves journey times, as people turning do not have to stop at the light but can continue at the same speed.[2] There are two types of slip lanes at intersections: slip lanes that end and require traffic to merge to join the main road, and slip roads that continue onto the main road as another traffic lane.


In Australia, before entering a slip road, drivers must look to ensure that their blind spots are clear of other motorists, cyclists, and pedestrians. Drivers must then give way to any pedestrians crossing the slip road. Before joining the main road from a slip road, drivers must give way to all other traffic even if it is faced with a give-way or with other traffic controls.[3]


In countries such as the United Kingdom in which partial conflicts between pedestrians and vehicular traffic are not permitted, slip lanes can be used as part of a "walk with traffic" facility. Normally, pedestrian signals in the UK operate on a full pedestrian stage in which all traffic is held at red, and all pedestrian crossings are given a green signal. With a slip lane, pedestrians can cross to the triangular island during the vehicle red phase and cross the road while the traffic from their approach has a green.[4]


The organisation Strong Towns argues that slip lanes exist to only prioritise the speed of motor traffic and calls for the removal of slip lanes on local streets.[5]

When poorly designed, slip lanes can be a dangerous design element. For reasons of urban design and pedestrian safety, many road-controlling authorities are actively removing them in urban and suburban settings.[6][7] Slip lanes may need to be removed if considerations such as pedestrian safety grow to a point that they override the desire to facilitate free passage for cars.[8][9]

To minimise risks of collision, slip lanes can be shaped to enter the traffic flow at an angle higher than the 45 degrees that is shown in the sketch. Such lanes are called high-entry angle slip lanes.[10]

See also


  1. ^ "Pedestrians crossing slip lanes" (PDF). Main Roads Western Australia. September 2002. Retrieved 8 November 2015.
  2. ^ Davis, Stephen Lee (5 November 2019). "Slip Lanes Would Never Exist if We Prioritized Safety over Speed". Strong Towns.
  3. ^ "Road Rule Changes". Archived from the original on 8 February 2008.
  4. ^ "Chapter 6, Traffic control". Traffic signs manual. London: Department for Transport, Northern Ireland. Department for Infrastructure, Scotland. Scottish Government, Wales. Welsh Government. 2019. ISBN 978-0-11-553744-8. OCLC 1134444798.
  5. ^ "Slip Lanes Would Never Exist if We Prioritized Safety Over Speed". Strong Towns. 5 November 2019. Retrieved 2022-01-05.
  6. ^ "Well Designed Right–Turn Slip Lanes". Federal Highway Administration.
  7. ^ "Cities Are Replacing Dangerous Slip Lanes With Space for People". Streetsblog. July 2018. Retrieved 4 June 2019.
  8. ^ "City Road Draft Master Plan" (PDF). Melbourne City Council. July 2015. Retrieved 8 November 2015.
  9. ^ "Slip Lanes be gone". Matt L. 2 October 2015. Retrieved 8 November 2015.
  10. ^ "Guidelines for the signing and layout of slip lanes" (PDF). NZ Transport Agency. November 1993. Retrieved 9 May 2017.