Lane-Change Response to Infrastructure Warning About Lane Closure in a Mixed Vehicle Fleet

Fostering the safe and efficient operation of road networks that include vehicles equipped with SAE International® Level 3™ (L3) automation and a cooperative automated driving system (C-ADS) requires an examination of these systems’ ability to interpret and correctly respond to infrastructure that was designed for human drivers (SAE International, 2020). Changeable message signs (CMSs) are one of the infrastructure elements that may be problematic for L3 automation systems. This research study used a driving simulator to assess the potential value of adding cooperative driving automation (CDA) alerts to a CMS. The study team manipulated whether the participants were equipped with a simulated L3 automation system; the source of information (CDA alert only, CMS only, or both the CDA alert and CMS); and the message type (informational or instructional). The results suggest drivers who received messaging from both a CDA alert and the CMS displayed “smoother” lane changes, as indicated by longer lane-change times, longer distances traveled, and less variability in their steering wheel angle in comparison to drivers who received the messaging only via the CMS. Of the drivers equipped with L3 automation capabilities, the majority (65 percent) disengaged the automation just before and during the lane-change maneuver. In contrast to conventional drivers, those equipped with the L3 automation capabilities displayed “less smooth” lane changes, as indicated by shorter lane-change times, shorter distances traveled, and more variability in their steering wheel angle. Drivers exposed to the informational message tended to initiate a lane changes soon after passing the CMS, relative to drivers who viewed the instructional message. The research team observed several interaction effects among all three experimental factors, and the authors review those observations in more detail in the Discussion section of this report. The overall findings support incorporating CDA alerts in tandem with CMS.