While Daytime Running Lights (DRLs) are proven to increase vehicle conspicuity during various times of the day, their safety effectiveness is still debatable. This study utilized various statistical techniques and a field study to assess the impact of the compliance rate, and the penetration of the Daytime Running Lights (DRLs) technology on the safety efficacy of regulatory headlight use signs. Daytime head-on and opposite sideswipe multivehicle crashes for Daytime Running Lights and non-DRLs equipped passenger vehicles on mountainous rural two-way highway sections with and without regulatory headlight use signs were examined in a matched case control design. Preliminary analysis showed that only 23% of vehicles involved in crashes on the study sections were equipped with DRLs. Although results from the odds ratios and ratios of odds ratios indicated some safety benefits of the headlight use signs, the safety benefits were statistically insignificant. The study concluded that the low compliance rate of 12% affected the safety effectiveness of the regulatory headlight signs. Transportation agencies should have different considerations when evaluating the safety effectiveness of compliance- and behavioral-based countermeasures.