A Simplified Simulation Model to Estimate the Storage Length of the Right-Turn Lane in Left-Hand Traffic at Signalised Intersections for Different Signal Phases and Cycle Timings

A large number of the current guidelines and models are used to estimate the right-turn lane (RTL) length in left-hand traffic at signalised intersections under split phase, in which the movement of traffic in the right-turn lane and through lane happen concurrently. There is a need to examine other phase types and timings as a part of the RTL design. This is particularly significant in the case of established intersections that cannot be modified due to physical constraints.

A MATLAB based simulation programme was developed to provide an estimate of the right-turn lane storage length for different traffic volumes in order to avoid the problems associated with blockage and overflow of the right turn vehicles in 95% of the traffic signal cycles. The model enhances flexibility when dealing with the complexity of the design of the storage length taking into account different signal phases and timings to overcome the aforementioned problems. The simulation model also takes into consideration the left-over queue from the previous cycle which was ignored by most of the previous studies.

The model input includes as a configuration matrix containing the sequence of operational states of the intersection. This ensures the flexibility and the simplicity of manipulating the data to reflect all phase types and timings. The model results have been compared against a recently developed analytical model in which similar signal phases and timings were investigated. The outcomes agree to the results that are obtained from the analytical model in most of the signal phases. The developed simulation model is flexible enough to be used further to simulate the situation when there is a large difference between the approaching and opposing traffic volumes and optimise the green time in case of split phase. In this study, the simplified simulation model for estimating the RTL storage length has been developed for the left-hand traffic countries; however, the study is equally applicable to the left-turn lane (LTL) in right-hand traffic countries.