Cooperative Intersection Collision Avoidance System (CICAS): Signalized Left Turn Assist and Traffic Signal Adaptation

The Cooperative Intersection Collision Avoidance (CICAS) program is a multi-year, cooperative research program with federal, state, academic, and industry partners. The CICAS-SLTA (Signalized Left Turn Assist) segment aims to address crashes caused by vehicles making left turns at signalized intersections that have no protected left-turn signal. This report addresses so-called Left Turn Across Path-Opposite (LTAP/OD) crashes, which account for more than 27 percent of all US intersection-related crashes. It describes direction problems, where drivers have cognitive, time pressure, or obstruction challenges making safe turn decisions with a permitted signalized left turn. In addition, the report relates this research to other US DOT Vehicle-Infrastructure Integration (VII) activities. The final goal is to show the feasibility of providing left-turn support and warnings to the driver through an in-vehicle interface.