What factor is essential for successful permissive left turns?

For successful permissive left turns, having adequate gaps in opposing traffic flow is crucial. This means that a driver making a left turn needs to have a clear and safe opportunity to enter the intersection without conflicting with oncoming traffic. If the gaps are insufficient, the risk of collision increases significantly as the driver may attempt to make the turn at an inopportune moment. Therefore, the ability to identify appropriate gaps is fundamental for the safety and effectiveness of permissive left turns.

Other factors, such as proper signage and traffic signals, play supporting roles in guiding and facilitating turns; however, they do not directly ensure that a driver can execute the turn safely amidst moving vehicles. High traffic enforcement may help in promoting adherence to traffic rules, but it does not affect the immediate need for clear gaps in oncoming traffic for a successful left turn.