| When several traffic signal-controlled intersections occur along an arterial, some form of coordination may be necessary to prevent the arterial vehicles from stopping at every intersection. Problems of arterial signal coordination arise when some of the signal-controlled intersections are part of a freeway diamond interchange. Signal coordination presents special problems at a diamond interchange due to the proximity to each other of the two ramp intersections, and because the interchange operates on a multiphase signal sequence.;The model was implemented for several signal progression offsets. In this case the simulation results showed that for a given traffic flow rate and pattern, the interchange will attain average optimum operating conditions at a particular signal offset value. The optimum interchange signal offset will vary for different traffic flow configurations. It was also observed that different traffic streams reach optimum performance levels at different offset values.;As a result of this study, it was recommended that whenever arterial progression is carried through a diamond interchange, an evaluation of performance impact should be conducted for the interchange and for each of the interchange traffic streams. It was also recommended that the simulation model that was developed during this study be further tested with data from more sites.;Since the impact of arterial signal progression on interchange performance has had limited study, and due to practical limitations of studying an actual diamond interchange, a discrete event computer simulation model was developed, validated and implemented. |
