Civil and Environmental Engineering


Document Type


Date of this Version



Published in Transportation Research Record: Journal of the Transportation Research Board, No. 2623 (2017), pp 10–18.

doi 10.3141/2623-02


Copyright © 2017 by National Academy of Sciences; published by SAGE Publications. Used by permission.


Platoon dispersion (PD) is the foundation of traffic signal coordination in an urban traffic network. PD describes the phenomenon by which vehicles depart from an upstream intersection as a platoon and begin to disperse before they arrive at the downstream intersection. Recently, advance warning flashers (AWFs) have been applied in many high-speed corridors. There is a need to update the traditional PD model to include the effect of AWFs. This paper examines the traffic flow dispersion patterns when an AWF is present and tests the hypothesis that the AWF will affect PD on a coordinated signal corridor. Platoon vehicles, which are not affected by the operation of the AWF, are used for comparison. Results show that when the AWF effect is included in the PD model, the smoothing factor F of the Robertson’s PD model ranges from 0.11 to 0.13. This range is smaller than the smoothing factor without the AWF effect. The platoon arrival time coefficient a ranges from 0.777 to 0.819 with the AWF effect. This is approximately the same as the default value of 0.8 in the TRANSYT simulation model. The PD coefficient β increases from an average of 0.11 with the AWF effect to an average of 0.24 without the AWF effect, which indicates an increase in roadway friction. It was concluded that AWFs increase the dispersion of the platoons, which might affect signal coordination.