Accounting for the Effect of Controller Characteristics in Estimating Delay for Permitted Left Turn Movements

The Highway Capacity Manual (HCM) equation for estimating control delay utilizes a parameter known as incremental delay factor, to account for the effect of controller characteristics on delay. For pretimed phases, coordinated phases, and phases set to maximum recall, a value of 0.5 is recommended. For actuated controllers, the HCM provides a set of values, ranging from 0.04 to 0.5. These HCM procedures are generalized, but they are applied to all traffic conditions. They do not accurately account for actuated controllers’ ability to accommodate delay; especially for permitted left turn movements which have a very stochastic traffic flow process. Therefore, there is a need to develop specialized methods that address complex traffic situations, in order to estimate delay accurately. This paper presents two empirical models for estimating the incremental delay parameter for permitted left turn movements at actuated signalized intersections. Results show improved delay estimation using the proposed models.