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Effect of Traffic Signal Countdown Timers and Speed and Red-Light Cameras on Operation and Safety

Almutairi, Omar Eid
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543840523279126

Abstract Details

2018, PhD, University of Cincinnati, Engineering and Applied Science: Civil Engineering.
The effects of two auxiliary devices, traffic signal countdown timers and speed/red-light cameras, on intersection operations and driver safety are investigated. The timers display a countdown clock from a certain light indication to the subsequent light indication. The cameras represent a type of automated enforcement technology used to detect and deter speeders and red-light runners. The literature reveals mixed results on the effects of timers and cameras on intersection operation and safety. These results may be affected by researchers’ varying assumptions regarding relevant parameters and definitions. Accordingly, the effects of these auxiliary devices on the startup lost time (SLT), saturation time headway (STH), and dilemma zone location and size are studied based on ground-truth data without any assumed parameter values. Observational data were obtained at two pre-timed signalized intersections, one equipped with cameras and one not. The intersections are highly similar in layout and timing phase design, and both have traffic signal countdown timers. Data on through movements were collected for one daytime each when the timers were turned on and off for each intersection. SLT and STH were estimated for each intersection type using one-way analysis of variance (ANOVA) and Tukey’s method. Then, a linear regression model was run on the estimated SLT and STH values to quantify the effects of each intersection type. The effects of the two auxiliary devices on the dilemma zone location and size were then investigated by modeling the observed maximum passing and minimum stopping distance based on real ground data. A logistic regression model was also run to quantify the effects of the auxiliary devices on stopping probability. The results revealed that both auxiliary devices reduce SLT but do not significantly affect STH. The cameras have a significant effect on shifting the dilemma zone location further downstream—changing it from type I to option zone—and increasing stopping probability. The timers have a significant effect on minimizing the size of the dilemma zone but do not affect stopping probability. Further, the presence of cameras reduces red-light violations, whereas the timers have little effect on red-light violations. Thus, the timers improve intersection operations by reducing SLT and enhancing safety through the minimization of the dilemma zone size. Cameras increase driver compliance with traffic laws, but this benefit is limited solely to the intersection equipped with cameras; many red-light violations were noted at the other observed intersection, disproving a spillover effect. Cameras also increase stopping probability and option zone size. Thus, the cameras are not recommended, and further studies are necessary to quantify the effects of the two auxiliary devices with different timing phase designs and yellow intervals. Moreover, the results indicate that the level of traffic enforcement heavily affects the dilemma zone’s location and size. Therefore, additional studies with different levels of traffic enforcement are needed to further calibrate the dilemma zone’s location and size under each level.
Heng Wei, Ph.D. (Committee Chair)
Jonathan Corey, Ph.D. (Committee Member)
Zhixia Li, Ph.D. (Committee Member)
Julian Wang, Ph.D. (Committee Member)
99 p.
Civil Engineering
Traffic Signal Countdown Timers; Speed and Red Light Cameras; Dilemma Zone; Startup Lost Time; Saturation Time Headway

Recommended Citations

Citations

  • Almutairi, O. E. (2018). Effect of Traffic Signal Countdown Timers and Speed and Red-Light Cameras on Operation and Safety [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543840523279126

    APA Style (7th edition)

  • Almutairi, Omar. Effect of Traffic Signal Countdown Timers and Speed and Red-Light Cameras on Operation and Safety. 2018. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543840523279126.

    MLA Style (8th edition)

  • Almutairi, Omar. "Effect of Traffic Signal Countdown Timers and Speed and Red-Light Cameras on Operation and Safety." Doctoral dissertation, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543840523279126

    Chicago Manual of Style (17th edition)

ucin1543840523279126
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This open access ETD is published by University of Cincinnati and OhioLINK.