Efficiency Assessment Of Green Time Utilization At Countdown Signalized Intersections

Binary regression models were developed, using data obtained from the driver behavior survey, to estimate the decision probabilities for different combinations of vehicle position (i.e. distance to the stop line) and available green time (i.e. time left before the transition to yellow phase). A comparison between the estimated decision probabilities for countdown signal and à priori decision-probabilities (determined from deductive reasoning) for traditional traffic signal supported a pattern of underutilization of green time for the countdown signal scenario.

The underutilization of green time was associated with the likelihood of drivers slowing down prematurely to stop in reaction to the visual display of available green time before the change of signal phase. Underutilization of effective green time translates into a lower saturation flow rate and hence reduced intersection capacity. The findings of this research could motivate additional studies pertaining to the determination of net operational benefits or plausibility of using countdown signal devices at urban traffic intersections in the United States.