Abstract: Two methods for evaluating the capacities of shared through and left turn lanes from"1994 US highway capacity manual"and"design criteria of city street in China" under various lane configuration,through and left turn volumes, and traffic signal timings were comparatively analyzed.Results show that when the left turn volume increases, the total traffic volume of shared through and left turn lanes decreases correspondingly.When the traffic signal period increases from 60s to 90s,the approach traffic capacity decreases under constant effective split.For constant total split,traffic capacity with long signal period increases slightly.When the left turn volume exceeds a threshold,the traffic demand will exceed capacity on the approach.In order to solve the problem,the signal phase design should be improved, including to implement a left turn protective phase.

Key words: shared through and left turn lanes, traffic capacity, split