The Effects of Restricted Sight Distances on Drivers at Simulated Rural Intersections

Abstract

Short sight distances at rural intersections can result in reduced safety including drivers choosing smaller gaps between oncoming vehicles (Yan & Richards, 2010). Conversely, increased sight distances may result in improved driver confidence, but not safety as seen at rail crossings (Ward & Wilde, 1996). Thus, simply increasing sight distances may not result in linear gains in safety. Establishing appropriate lower and upper-visibility limits at rural intersections will minimize operational costs for clearing and grubbing labor and may reduce serious injury and fatal crashes by promoting safer crossing behavior around rural thru-STOP intersections. This driving simulation study will examine intersection visibility and other intersection design factors that influence driver behavior at rural thru-STOPs. Time to collision, or TTC, is a primary motivating factor on driver decisions to cross intersections. Drivers’ TTC perception is a function of oncoming vehicle speed, distance, and rate of retinal expansion (tau; Hancock & Manser, 1997). We hypothesize TTC factors may interact with confidence in intersection crossing judgments. Specifically, when people must quickly make judgments, their confidence must be estimated after the decision has been made, but if the time pressure is not high and the decision is not immediate, people’s judgments and their confidence in those judgments can both be considered prior to action. This can be problematic because people are normally overconfident in their judgments (Harvey, 1997). The present study comprised a crossing judgment block, and a mainline drive block. The experimental stimuli were validated by engineers with experience in rural intersections, who rated the simulated intersections as “significantly representative” to real-world intersections through an average rating score of 5.25 ( SD = 0.5) on a 7-pt scale. This was done to ensure that the study findings would be more likely to be applicable to world intersections. The goal of the study is to identify whether sight distance and other variables, including speed for the judgment task and vehicle proximity to the intersection for the mainline drive task, impact safety at rural intersections.