This study evaluated the safety effectiveness of the flashing yellow arrow (FYA) treatment at signalized intersections in reducing the frequency of left-turn crashes. The study divided the treatments into seven categories depending on the phasing system in the before period. The first five categories had permissive or protected-permissive phasing in the before period and experienced a reduction in left-turn crashes and left-turn-with-opposing-through crashes at the intersection level. Intersections in categories 6 and 7 had at least one protected left-turn phase in the before period, and after phasing had an FYA protected-permissive left-turn phase without time-of-day operation (category 6) and with time-of-day operation (category 7). These categories experienced an increase in left-turn and left-turn-with-opposing-through crashes. Economic analysis for categories 1–5 showed the treatment is cost effective in improving safety. B/C analyses were not conducted for categories 6 and 7 because these treatments are typically used for capacity improvements rather than safety.
 

This report will benefit safety and traffic engineers and safety planners by providing greater insight into intersection safety.