Impact Assessment of Driver Distraction by Cellphone on Start-up Lost-time and Average Saturation Headway at Signalized Intersections Based on Vehicle Position in the Queue

Alshabibi, Nawaf · 2021 · Crossref

DOI: 10.3311/pptr.16785

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study investigates the impact of driver distraction caused by cellphone usage on the capacity and level of service (LOS) of signalized intersections, specifically focusing on Start-up Lost Time (SLT) and Average Saturation Headway (ASH). While previous research has largely focused on safety and reaction times, this paper addresses a gap in understanding how distraction affects traffic flow metrics under specific operational conditions: one green time operation per approach and a 240-second cycle length. The research was conducted in the Dammam Metropolitan Area, Saudi Arabia, to provide data relevant to these specific intersection configurations. The methodology involved field data collection at 24 signalized intersections during evening peak hours (5–6 PM) from September to October 2019. Two observers recorded vehicle discharge times and driver distraction status (calling, texting, or none) for mid-through lanes. The study analyzed 183 useful cycles, comprising 2,407 data points for SLT and ASH. Data were categorized based on the position of distracted drivers in the queue: the first to fourth vehicles, the fourth to tenth vehicles, or both. Statistical analysis included normal distribution tests and z-tests to compare SLT and ASH values between cycles with and without cellphone usage. The findings reveal a statistically significant increase in SLT of approximately 0.7 seconds when drivers used cellphones, particularly when the distraction occurred within the first four vehicles in the queue. The probability value for this increase was 0.01, confirming significance. In contrast, the study found no statistically significant increase in ASH; the observed increase of 0.09 seconds yielded a probability value of 0.31, which is not significant. The impact on SLT was most pronounced when distracted drivers were closer to the stop line, indicating that delayed reaction times at the start of the queue propagate through the intersection discharge process. The significance of these results lies in their implication for traffic engineering and signal optimization. The 0.7-second increase in SLT reduces effective green time, leading to a decrease in intersection capacity by approximately 13 vehicles per hour, increased total delay, and deteriorated LOS. The study concludes that cellphone usage primarily affects the initial discharge of vehicles rather than the saturation flow rate. These findings assist transportation officials in adjusting signal timing and capacity calculations to mitigate the operational impacts of distracted driving, particularly in environments with long cycle lengths and single-approach green times.

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• mobile phones

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: observational prevalence, behavioral performance data