This paper considers some effects of platoon size and degree of dispersion on dispersion distance for progressive traffic movements through coordinated traffic signals, and establishes a mathematical relationship for determining a critical block length for signal grouping. It reviews previous literature, and then develops a mathematical model. To develop qualitative and quantitative definitions of a platoon, a methodology must be derived for calculating the vehicular headway limit of a platoon for multi-lane approaches. To test the model, field observations were conducted along a four-lane urban main road in Taipei, Taiwan; 236 platoons of variable size were observed. A regression analysis was applied to the data collected about these platoons. The critical length for signal coordination was estimated as a linear function of original platoon size and platoon completeness ratios, increasing with the former variable and decreasing with the latter. Thus, for a given platoon completeness ratio, critical block lengths on heavily travelled main roads would be longer than those with relatively light traffic.
Abstract