Connected Vehicle (CV) technology has many promising features and applications for detecting dangerous driving scenarios and providing warning messages to drivers. The effectiveness of these warning systems is dependent on the vehicles’ ability to communicate with other surrounding vehicles. Therefore vehicles within range must also be equipped with CV technology. Due to this limitation, the effectiveness of CV safety applications is dependent on the market penetration (MP) of CVs within the network. This study evaluates the effectiveness of three CV safety applications, namely: Blind Spot Warning (BSW), Forward Collision Warning (FCW), and Do Not Pass Warning (DNPW) applications at different MP rates using a driving simulator test bed that was developed in the driving simulator laboratory at Louisiana State University (LSU) that allows vehicles to communicate and transmit warning messages within the virtual environment.
The simulator environment provided drivers with visual and auditory warnings for BSW and DNPW but omitted auditory warnings from the FCW application. User surveys were also collected from the participants.
- Blind Spot Warning (BSW):The BSW system was tested at zero MP (no CV communication), low MP (25 percent), medium MP (50 percent) and high MP (75 percent). The driving behaviors of 81 participants were observed during lane change maneuvers with and without CV communication. A proximity-based threshold was used to trigger a warning as a CV approached the simulator vehicle’s blind spot. The significance each MP had on the minimum time-to-collision (TTC) and the variance of the speed of the subject vehicle and blind spot vehicle were then compared.
- Forward Collision Warning (FCW): The FCW application was designed enabling a lead vehicle to communicate alert messages to the simulator when certain time-to-collision (TTC) thresholds were reached. The effectiveness of the FCW application was tested on aggressive and conservative categories of 30 drivers by assuming a 100 percent MP.
- Do Not Pass Warning (DNPW): For DNPW, an 8-second TTC threshold was designed to warn drivers of oncoming vehicles on a two-lane, two-way rural roadway. The effectiveness of the DNPW application was tested by using 12 participants who were randomly assigned two of the four scenarios/levels of market penetration where they performed five overtaking maneuvers in each scenario.
- The safety warnings helped to significantly increase the subject vehicle’s minimum TTC during the presence of the blind spot vehicle. At low MP, BSW applications had no significant safety improvements but in medium and high levels of MP, significant safety improvements were observed due to additional information available to drivers in the network. Significant increases in the mean ranks of minimum TTC from zero (582.87) to medium (671.95) MP (a 15 percent increase), and from zero to high (635.54) MP.
- The participants’ survey responses showed that 75 percent of the participants with high MP and 43 percent of the participants with medium MP felt more comfortable performing lane changes with the visual warnings of BSW.
- The FCW test results showed that aggressive drivers compared to non-aggressive drivers significantly changed their driving behavior when exposed to alert messages by slowing down more at intersections and increasing their TTC.
- During the DNPW tests, there was a slight increase in mean TTC from zero MP, 6.22 seconds, to medium and high MP, 6.64 seconds and 6.3 seconds, respectively. This difference was not significant. The unchanged TTC value for the DNPW system tests suggests that a DNPW system with limited CV technology and less than 100 percent MP was not an effective means for increasing gap acceptance and avoiding dangerous overtaking maneuvers. However, the warning system significantly increased the headway between the driver and the slow-moving vehicle before the maneuver.
- Based on the participants’ survey, at high levels of MP, half of the participants found the DNPW warning system to be distracting. This was not the case at low and medium MP, where 0 percent and 17 percent, respectively, found the warnings to be distracting. The majority of participants found the warning system to be useful (61 percent) and felt more comfortable performing overtaking maneuvers with the warning system (56 percent), but did not show any indication of becoming dependent on the warning messages.