Engineering Countermeasures for Left Turns at Signalized Intersections: A Review

Left turn crashes can impact the safety of drivers due to speed and angle at which they occur. turns are specifically reported affect older more than other types crashes. This paper provides a review existing engineering countermeasures that have been evaluated improve driver left turns. Twentyeight studies on signal displays (protected turns, flashing yellow arrow, digital countdown timers), intersection geometry (offset lanes, diverging diamond interchange, roundabouts, exit lanes for turn, bay extension, contraflow lanes), warning systems (infrastructure systems, in-vehicle systems) reviewed. Eighteen were in field, nine laboratory environments, one online. All demonstrated varying levels effectiveness. We found protected be most effective countermeasures. Advantages disadvantages each countermeasure research shortcomings evaluation discussed. Review findings may help practitioners researchers guide drivers.