This study examined how implementing automated speed enforcement (ASE) may influence driver attention and behavior in work zones by replicating a work zone in a driving simulator and having volunteers drive through it under different speed enforcement conditions: no enforcement (control), police car present, ASE, and ASE with dynamic “your speed” signs (ASE+DSDS).
The simulated work zone was a 9.2 mile long segment of U.S. Route 169 between Jordan and Belle Plaine, Minnesota and composed of: a 2 mile introductory area, 1.2 mile transition area, 5 mile activity area, and 1 mile conclusion area. The activity section was divided into four subsections: upstream (of enforcement), enforcement, downstream 1, and downstream 2.
The primary task during the experiment was to follow a lead vehicle at a close, but safe, distance along the route while adhering to the 55 m/hr work zone speed limit. The lead vehicle drove at a constant speed of 55 m/hr initally, then changed speed using a sine function (mean of 55 m/hr, min of 40 m/hr, max of 70 m/hr). Participants were told some of their incentive would be deducted if they exceeded the speed limit. This was done to motivate participants to avoid speeding, though no actual deduction was taken. All four experimental drives were performed consecutively in a randomized order.
A secondary task was used to give participants another activity to do while driving. The participant would press a target arrow, causing peripheral arrows to rotate for about 1.5 seconds. When they stopped, the participant had to identify how many peripheral arrows matched the target. Participants could choose how many secondary tasks to complete.
Analyses of driving performance, distraction and attention measures using a 3x4 mixed model ANOVA with age group (young, middle-aged, and older) as a between-subjects measure and speed enforcement type (control, ASE, ASE+DSDS, and police presence) as a within-subjects measure. Driving performance and eye tracking results were analyzed and are described by work zone segment: transition, upstream, enforcement, and downstream zones.
Deploy automated speed enforcement with dynamic "your speed" signs in work zones to heighten visual attention from drivers. In work zone speed enforcement scenarios using automated speed enforcement coupled with dynamic "your speed" signs, this study found that drivers fixated on a secondary task less frequently compared to other scenarios and heightened their visual attention to the work zones. Older drivers were also more compliant with the speed limit.