Investigating Driver Response Time to Freeway Merge Advisories in a Connected Vehicle Environment

Vehicular conflict is one of the major causes of congestion in freeway merge areas. With the emerging connected vehicle environment, more proactive strategies can be developed and implemented to improve merging operations with enhanced safety and mobility. The freeway merge assistance system, made possible with connected vehicles, ensures smoother merging through the early identification and dynamic notification of merging opportunities by advisory message. However, given that the effectiveness of this mobility application depends entirely on drivers' responses to the advisory messages, a proper understanding of driver response to the new generation of dynamic advisory messages is a necessity. A detailed analysis of driver response time to advisory messages from the freeway merge assistance system was conducted on the basis of the data collected in a field test with 68 naive participants. The analysis results showed that the perception reaction time increased as the available gap size decreased. An estimated 0.64-s difference was observed between cases with large and small gaps and implies varied perception reaction times for various traffic conditions. Second, the perception reaction time decreased as the advisory became more direct and proactive, with an observed 1.30-s decrease in perception reaction time between the most direct and indirect advisories. It is therefore recommended that advisory messages should be direct and clear. The actual lane-changing time did not change much, regardless of advisory type or available gap size. The implications of these results are of significance in the design and implementation of connected vehicle enabled mobility applications.