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Actuated signal operations for congested conditions were evaluated with a simulation study at diamond interchanges. Both three-phase and four-phase with two-overlap phasing strategies were employed, with four ramp spacings and traffic patterns. The performance difference was discussed with throughput, average delay, and total stops. Results showed that four-phase control gave less or comparable average delay (or more throughput) for most traffic patterns at ramp spacings of 122 m or more. Three-phase control gave less delay (or more throughput) when an interchange had a balanced traffic pattern from all external approaches. In terms of stops, four-phase operation gave less stops than three-phase operation for all congested conditions investigated. Analysis results indicated that marginal operational benefits could be obtained when ramp spacing was designed between 122 and 183 m. In addition, several regression models were developed for use in performance estimation for congested traffic conditions. The test results showed that the models could provide good performance estimation of congested signal operation at diamond interchanges. [ABSTRACT FROM AUTHOR]

The performance of three traffic analysis tools: CORSIM, SIMTRAFFIC, and SYNCHRO was investigated for application to diamond interchanges. Actuated signal operation was implemented for different ramp spacings and traffic patterns. The performance differences were discussed for three performance measures: Cycle length, average delay, and total stops. Our research showed that the two microscopic models (CORSIM and SIMTRAFFIC) produced similar performance, but the macroscopic program SYNCHRO provided different performance trends. It was found that SYNCHRO 4 and SIMTRAFFIC produced different phase splits for the same input data. Therefore, there is a possibility that estimated delay (or stops) performance could vary depending on the model selected. Our results also indicate that SYNCHRO 4 apparently does not reflect some progression effects properly, thus the application of SYNCHRO 4 for diamond interchanges should be used with caution. Either SIMTRAFFIC or CORSIM used in conjunction with hardware-in-the-loop simulation should be used for analysis of actuated diamond interchanges. It was also found that SIMTRAFFIC tended to model queue spillback conditions more restrictively at the upstream intersection than did CORSIM or SYNCHRO. [ABSTRACT FROM AUTHOR]