Enhancement of traffic management algorithms for UK motorways

The overall aim of this work is to review and improve traffic CM algorithm to delay the onset of flow breakdown. The results indicated that compared to other two classic models, the Underwood model was able to match the field data on the M25 motorway consistently and capture the speed-flow relationships successfully, in terms of larger R-squared coefficient (R2) and smaller average values of root mean squared error (RMSE). In addition, it was found that Gaussian function can describe the relationship between flow values at the turning points of traffic speed and flow curve and the threshold of the CM algorithm. The fitted traffic speed and flow curve showed that the values at the turning points were significantly reduced under light and heavy rainfall. Thus, the threshold values of the CM algorithm should be optimized according to the determined Gaussian function in the present work.