The selection of appropriate intergreen times is an essential safety consideration for any traffic signal design. If the times chosen are too short, collisions or near-misses could result. At the other end of the scale, times that are too long impact on efficiency. Guidance states that the suitability of intergreen times can be determined through on-site observation. But how effective really is this? How can it be determined that every combination of road user type on the gaining and losing phases makes a safe transition? The available intergreen guidance does not consider the specific geometry of a road or it’s gradient and no account is taken for the different performance characteristics of the wide range of vehicle types in use on our roads. A new method of calculating Intergreen times is presented in this paper that addresses these shortcomings, creates safe and efficient intergreen times for all users and removes the burden on signalling scheme designers.
- October 3, 2023
- John Nightingale