Webster’s Delay Formula – revisited

Kurzfassung

The equations developed byWebster in his famous 1958 report[10] are still the basis of traffic signal planning today. They are being used in handbooks like the HCM and similar instruments world-wide. However, the handbook approach typically works with approximations to the original equations which have stood the test of time, but may nevertheless not be the best to be done today. This work analyzes Webster’s approach and advocates a more modern use of it which utilizes the tremendous advances in computer hardware and software. This is being done by comparing approximations to exact solutions, and by a comparison between various models and Webster’s equations itself. It is shown that there can be significant differences in the calculation of optimal cycle times and consequent delay times.