Junction Assessment Tool and Cycle Level of Service
Junction Assessment Tool and Cycle Level of Service
TMS have recently carried out a Stage 2 RSA on a Transforming Cities Fund (TCF) Public Realm Improvement Scheme, which involved carriageway realignment, footway widening, measures to restrict through traffic movements, and the reallocation/additional provision of Bus Shelters.
As part of the funding process the scheme had been designed to align with LTN1/20 guidance, namely improved bus journey times and provision for active travel. A balance for the use of the existing highway corridor was required to provide sensible and safe carriageway widths whilst maintaining suitable widths for cycleways and footways.
LTN1/20 guidance contains tools to give local authorities flexibility on the infrastructure design and sets out a measurable quality threshold to achieve when designing cycling and active travel schemes, namely the Junction Assessment Tool and Cycle Level of Service mechanism.
The Junction Assessment Tool (JAT) and Cycle Level of Service (CLoS) are new mechanisms introduced in LTN1/20 to set minimum quality criteria. These tools give local authorities flexibility on design of infrastructure but set an objective and measurable quality threshold.
Both mechanisms are comprehensive. A JAT examines all potential cycle movements at a junction, not just those that may be associated with a designated cycle route, to identify the potential for conflicts and should be used whenever new and improved junctions are being designed. The junction assessment should be represented graphically, colour coding each movement either red, amber, or green. LTN 1/20 outlines the colour coding as:
Red – Where conditions exist that are most likely to give rise to the most common collision types, then the movement should be represented on the plan as a red arrow.
Amber – Where the risk of those collision types has been reduced by design layout or traffic management interventions, then the movement should be coloured amber.
Green – Where the potential for collisions has been removed entirely, then the movement should be coloured green.
‘Green’ should be taken to mean suitable for all potential cyclists; ‘red’ means suitable only for a minority of cyclists (and, even for them, it may be uncomfortable to make). Green movements will exceed the standards that have typically been achieved in the UK to date.
A worked example of how to apply the tool can be found in Appendix B of LTN1/20
Image source: LTN1/20
The CLoS tool includes a simple scoring assessment based on attributes of the five design criteria (Coherent, Direct, Safe, Comfortable and Attractive), which can be used to identify strengths and weaknesses, and therefore what the design needs to address. The tool includes some factors that are considered to be ‘Critical Fails’ – results that represent unsafe conditions for cycling which must be addressed (or an alternative route found). This tool can be found in Appendix A of LTN 1/20.
For the scheme that TMS were involved in the JAT showed that there were some improvements for cyclists along the scheme corridor. A high percentage of green and amber arrows, however due to current highway constraints (corridor widths/third party land) there were several red arrows identified for right turning cyclists deviating from the main line. However, in justification it was considered that the number of cyclists making these right turns would be very low.
The Scheme CLoS achieved a score of 84%, 14% above the desired score and therefore was considered to be acceptable for the DfT.
If you have a scheme of this nature that requires our help on, then please call us on +44 (0)24 7669 0900 or alternatively please email Lorna Styring.
