Left turns can be one of the most dangerous maneuvers. Making a left turn requires drivers to cut across oncoming traffic. So if there is no green arrow that explicitly gives the turning vehicle the right of way, the driver of the vehicle must be extremely careful to not cause an accident with any approaching vehicles.
According to the National Highway Traffic Safety Administration (NHTSA), 22.2 percent of intersection crashes involve left turning vehicles. This may be a result of a driver misjudging the speed of an oncoming vehicle, obstruction in view, attempting to beat the yellow light, or running a red light.