Driving Simulator Study for Connected Emergency Vehicles in Washington, D.C. Found More Than 60 Percent Decrease in the Distance To Reduce Speed With Connected Vehicle (CV) Alerts at High Market Penetration.
Study Examined the Potential of Vehicle-to-Vehicle (V2V) Communication in Expediting Driver Responses to Emergency Vehicles.
Washongton DC, District of Columbia, United States
Response to Emergency Vehicles When Driving in a Mixed Vehicle Fleet
Summary Information
Connected emergency vehicles have the potential to enhance early detection by drivers, extending the distance at which they become aware of an approaching emergency vehicle. The integration of connected vehicles (CV) could improve emergency response times by enabling more efficient traffic clearance. Timely notifications allow drivers to proactively create a clear path, helping responders reach incidents faster. However, as CV adoption is expected to be gradual, some drivers may receive real-time alerts while others, in non-connected vehicles, may not have access to the same information. This study examined the potential of vehicle-to-vehicle (V2V) communication in expediting driver responses to emergency vehicles using a driver simulator. Specifically, it analyzed how drivers adjusted their speed and position, where they directed their attention, and how they engaged with other road safety measures in response to emergency vehicle alerts.
METHODOLOGY
The study recruited 96 drivers from the Washington D.C. metropolitan area, who operated both manual and Level-2 automation vehicles in a driving simulator, either with or without CV alerts. Participants navigated an 18-mile, undivided two-lane road in as semi-urban setting. After a period of driving, each participant became the third vehicle in a four-vehicle string, during which an emergency vehicle approached from behind. Half encountered it at 11 miles, the rest at 2 miles. The study examined three levels of market penetration (MP) for CV alerts: (1) “No MP”: None of the surrounding vehicles received an alert about the approaching emergency vehicle, (2) “Low MP”: The vehicle directly in front of the participant received an alert and responded by pulling onto the shoulder, and (3) “Full MP”: All three vehicles in the string received and responded to the alert. Additionally, participant vehicle connectivity was manipulated, with half of the participants receiving an in-vehicle message notifying them of the approaching emergency vehicle. The study measured participants' response time, vehicle kinematics, and eye-tracking data to assess their reactions to the emergency vehicle under different connectivity scenarios.
FINDINGS
The main findings of this study are as follows:
- Within MP levels, the participants receiving CV alerts tended to reduce their speeds sooner (i.e., travel less distance) than the participants not receiving alerts. For example, at Full MP, the mean distance to reduce speed showed an approximate 63 percent decrease for manual vehicles equipped with CV alerts compared to those without .
- At Low MP, the mean distance to reduce speed decreased by approximately 62 percent and 67 percent for Level-2 automated and manual vehicles, respectively, when equipped with CV alerts.
- Level 2 vehicle drivers with CV alerts in full MP reduced speed 95 ft earlier on average than those in low MP.
- Eye gaze tests showed that regardless of MP level, participants with CV alerts tended to spend 7 percent less time gazing at the roadway.
- For driving speed, participants with CV alerts in low MP drove 6.9 mph slower, and those in full MP drove 4.6 mph slower than the no MP group
- The results also found that in low MP, participants with CV alerts had a 151 ft shorter following distance than those without. In full MP, Level 2 vehicle drivers followed 98.4 ft closer than manual drivers.
