The aim of signal coordination is to minimize delay and number of stops at all intersections. The simple case of the coordination effect for one link between two intersections with 0.5 green ratio had been discussed and revealed theoretically. However, it is not clear for any green ratios. In this paper, the conception of coordination effect is reexamined and a general formula is introduced. The coordination effect is formulated with cycle length, link length and round travel time for any green ratio. This study reveals the followings. The coordination effect is high when round-trip travel time equals to cycle length or N-times match of cycle length. The coordination effect is low when round-trip travel time equals to green time (= red signal start point) or N-times match of cycle length plus green time.
As implementation of roundabouts is being discussed at more numbers of places after the partial revision of Road Traffic Law in 2014, quantifying the impact of heavy vehicles on entry capacity is an important and urgent task in Japan. The objective of this study is to estimate passenger car equivalent (PCE) of heavy vehicles at roundabouts in Japan. Since the number of actual roundabouts is still limited, this study adopts a microscopic traffic simulator for obtaining entry capacity under various heavy vehicle percentages in either entry or circulating flow. Then, passenger car equivalents at entry and circulatory roadway are derived based on the simulated capacities. As a result, it is found that the estimated passenger car equivalent is higher at entry than at circulatory roadway. At the end, entry capacity with heavy vehicles in both entry and circulating flows simultaneously is reasonably calculated by using the estimated passenger car equivalents.