Real-Time Driver Alerts to Improve CMV Safety in California Work Zones: A Naturalistic Study

Commercial motor vehicles (CMVs) are disproportionately involved in crashes around work zones. We seek to reduce these crashes via location-based in-cab alerts ahead of work zone activity. It was hypothesized that alerted drivers would reduce their speed, and that they would remain alert for traffic hazards as they passed through work zones. This would in turn reduce CMV-involved crashes and associated injuries and fatalities. Participants comprised existing users of a mobile application that provides free safety alerts exclusively to commercial drivers. Experimental group vehicles received a pop-up notification and audible chime 500 m before work zones, control group vehicles received no such alert. Location data was collected for all CMVs 30 s before alert through 5 min after the alert geofence, which was used to determine vehicle speed. An anonymous driver survey was also deployed in November – December 2024 via email to assess driver perceptions of the alerting experience and the safety impact of these alerts. Analyses from April 1 – December 23, 2024 for 228,713 vehicle visits at 4,080 unique work zones across nine counties in California indicate that, within the first 10 s post-alert, alerted drivers traveling above 55 mph reduce their speed by up to 0.5 mph more than the control group (p = .02), with a 30% greater magnitude of speed reduction. Lane-specific alerts may also be more effective than generic alerts, with slopes of deceleration up to 1.5 times steeper (p < .001). A survey of drivers participating in the present study (N = 422) found that 82% of drivers reported slowing down when receiving these alerts and 83% reported paying increased attention to their surroundings. In-cab notifications of active work zones in California appear to promote safer driving behaviors among commercial drivers exceeding the CMV speed limit. More informative alerting may have a more pronounced impact. Drivers appear to perceive these alerts as helpful in promoting safer driving behaviors.