Trials of segregation set-back at side roads: Overview report and recommendations (TRL703)

  • Published: TRL, 2014
  • Authors: Dr I. York, V. Chesterton & M. Benton
  • Date Added: 28 Aug 2016
  • Last Update: 28 Aug 2016
  • Format: pdf


Provides an overview of a set of four trials investigating the effects of different set back distances of a kerb segregated cycle track from a side road junction. The objectives of the trials were to investigate what distance of set back minimises the risk of conflict between all road users and what distance is most preferred by different road user groups.

The three track trials used video observations to measure speed, in lane position and stopping position. Questionnaire were used to understand user perceptions.


Three of the trials were based at a specially designed (off road) side road junction setting with a one lane approach, with the fourth using a driving simulator of a similar scenario with a two lane approach. The two set back distances were 5 metres and 20 metres. Drivers were approaching the junction at 30 mph.

Key Findings:

  • Video observations of the track trials demonstrated that car drivers’ speed and turning path was largely unaffected by the segregation set back distance until it was within 5 metres of the junction.

  • At 5 metres from the junction, the kerb is sufficiently close to result in a tightening of the turning radius, making it necessary for drivers turning left into the side road to slow down. This can result in the car having a position further away from the kerb.

  • The driving simulator trial found that in a two lane approach scenario, there was no difference in speed and position of car drivers in the 5 metre and 20 metre scenarios. This suggests that segregation in this setting would need to be brought even closer to the junction in order to have an effect, as there are other aspects such as the width of lanes contributing to a larger turning radius for drivers.

  • The driver simulator trial showed that the presence of a cyclist at a conflict point resulted in drivers reducing their speed. When a conflicting cyclists was present, drivers not only slowed at the junction, but also on approach to the junction, waiting for the cyclist to go straight ahead before turning left into the side road.

  • The track trial observations showed that on in a 5 metre set back situation, left turning drivers who overtook cyclists on the approach to the junction, allowed more lateral space between them and the cyclist.

  • Tighter geometry at the junction was found to result in less encroachment into the cycle lane and improved driver visibility of approaching cyclists.

  • Drivers preferred a greater set back distance from the junction.

  • Cyclists were split between preferring a shorter or longer set back distance. This was related to variations in cyclist views on the benefits of segregation. Some cyclists expressed concern about being able to take a good road position when passing the junction and that drivers would not give way when turning left across the cyclists’ path.


Cycle tracks, segregation, junction, left turn, conflict with other users


Compares how different set back distances of a kerb segregated cycle track affect safety at a side road junction.