Driver Compliance in Daytime Headlights Zones in the U.S

Aims: Observe driver compliance with daytime headlights requirements along two-lane highways in California and Arizona. Determine overall compliance rates, while identifying any statistical differences between highways.

Study Design: Travel along highways having daytime headlight use requirements during daylight hours, recording ambient conditions and compliance. Distinguish between cars, large commercial trucks, and motorcycles, and between manual (low-beam) and automated (very low-beam) headlights. Add supportive information from synergistic research.

Place and Duration of Study: California State Routes 4, 18, 74, 247, and U.S. Highway 95 in Arizona, during September 2010, and June and July 2015, over seven data collection days during the summer, and one on the first day of autumn.

Methodology: Calculate average driver headlight compliance rates and deviations to a 95% level of confidence. Assume that compliance follows a normal probability distribution pattern.

Results: A total of 758 motor vehicles were observed. Removing the 104 vehicles observed on a “cloudy” highway, 266 of the 654 drivers were using their headlights (40.7% ± 3.6% compliance). There was no difference between the proportions of compliant drivers on the six highways (95% level of confidence). A total of 66 of 104 drivers used their headlights under cloudy conditions (63.5% ± 9.6% compliance). A Facebook survey of 24 respondents found that 20% of drivers were unaware of daytime headlights zones (DHZs), and an additional 13% were deliberately noncompliant. Interviews of two California Highway Patrol officers revealed that citations for noncompliance were “not popular” (among the officers), and that there was some skepticism as to the effectiveness of the requirement.

Conclusions: Further observation is needed under cloudy skies to develop a more precise proportion of compliance. The low compliance suggests that the effectiveness of DHZs cannot be truly assessed. Compliance might be improved with enhanced driver education, as to their existence and purpose, less reluctant enforcement, a revised headlight sign design, and more frequent signing.