Influence of signal countdown timer on efficiency and safety at signalized intersections

Signal countdown timers (SCTs) are expected to help drivers with better decision-making processes. Because of the inconsistent outcomes from previous studies associated with them, the present study evaluates the influence of SCTs on intersection efficiency and safety by conducting “before and after” study at three signalized intersections located in New Delhi. A methodology is proposed to estimate the start-up lost time at signalized intersections under highly heterogeneous condition. Green signal countdown timer was found to have no influence on saturation flow, though its red component helped reduce the start-up lost time significantly. These two components also affect the red light violations at the intersection locations — by increasing violations during the last 10 s red and decreasing them during the initial 10 s of red. Timer-off scenario enlarged total ranges of both Type I and II dilemma zones at the onset of amber and brought Type II dilemma zone earlier.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author