Drivers frequently encounter Type II dilemma zones at signalized intersections,
where the decision to stop or proceed during the onset of a yellow indication
can be ambiguous. Decision-making relies on drivers’ expectations of the yellow
change interval duration and behavioral factors. While boundaries of these zones
are well studied, less is known about how familiar drivers are with their local
yellow indication laws, which vary from state to state, and whether their
typical reactions to yellow indications align with the laws.
Existing interventions like signal timing adjustments, improved vehicle
detection, and advance warning signs reduce the number of drivers caught in
dilemma zones but may not reach distracted drivers. In-vehicle alerts tailored
to dilemma zone scenarios are a potential solution not yet implemented widely in
North America. This study addresses how drivers may interpret these alerts.
A web-based survey of 640 licensed drivers in Michigan and Washington (ages
18–85) assessed respondents’ knowledge of their state’s law, typical responses
to yellow indications, interpretations of proposed in-vehicle alerts, and
preferences for alert modality, frequency, and placement. These states were
selected for their differing yellow indication laws—restrictive in Michigan,
permissive in Washington. Nine alert visuals were tested, including pairs of
implicit and explicit messages, and were inspired by or designed to address gaps
in prior research. Respondents evaluated these alerts in response to
hypothetical intersection scenarios that varied by the presence of other
vehicles.
Results revealed a prevalent misunderstanding of local yellow indication laws
across both states. Statistical analyses showed significant differences in
rankings among the nine alert visuals, and explicit messages showed higher rates
of correct interpretation. Findings show overall driver support for dilemma zone
alerts, but higher receptivity in drivers who more frequently use other ADAS
features and lower receptivity in drivers within older, but not the oldest, age
groups. Future research could explore whether these alerts promote safe
behaviors aimed at crash avoidance.
