On the periodicity of traffic oscillations and capacity drop: The role of driver characteristics

• Traffic hysteresis arises by variable driver characteristics within each driver.
• We explain the mechanism of periodicity of traffic oscillations.
• Aggressive driver behavior leads to hysteresis loops that induce the upstream propagation of oscillations.
• Larger hysteresis loops induce larger oscillation growth.
• Variable driver characteristics induce capacity drop.

This paper shows that traffic hysteresis arises due to variable driver characteristics within each driver and has a profound reproducible impact on the periodicity and development of traffic oscillations and the bottleneck discharge rate. Following an oscillation, traffic initially exhibits lower density and flow; then it evolves toward and eventually exceeds the equilibrium, whereupon another oscillation is instigated by an aggressive driver(s) with relatively small response time and minimum spacing. Thereafter, traffic reverts to lower density and flow and repeats the evolutionary cycle. Aggressive driver behavior also leads to hysteresis loops that induce the upstream propagation of oscillations; with larger hysteresis loops inducing larger oscillation growth. Our finding also suggests that the bottleneck discharge rate can diminish by 8–23% when drivers adopt larger response times in reaction to disturbances. This finding suggests that existing capacity-drop theories, with lane-changes as the main factor, may be incomplete.