How an energy measure reached the intersection
During the 1970s oil crisis, the United States looked for ways to reduce fuel use, including fuel burned by vehicles that were moving slowly or not moving at all. Allowing a driver to turn right at a red light after stopping offered a modest opportunity: if the road was clear, the car could proceed instead of idling through the rest of the signal cycle.
The practice was not invented everywhere at once, and some places had allowed it before the crisis. But federal energy-conservation policy helped make it a broader national measure by encouraging states to permit the turn. A small change in driving rules became part of a larger effort to make existing traffic flow use less fuel.
A shortcut with conditions
A red light still means stop. A driver considering a right turn must come to a complete stop, check for pedestrians and cyclists in the crosswalk, and yield to traffic with the right of way. The turn is allowed only where signs or local rules do not prohibit it; intersections may also have restrictions that vary by state or municipality.
The fuel logic is straightforward, though the savings from any single turn are small: avoiding an unnecessary wait can reduce idling and keep a vehicle from spending extra time in a stop-and-go queue. The policy also changes who must watch for whom. A driver turning across a crosswalk may encounter someone who has a walk signal, so the time saved by the car depends on careful yielding.
That tradeoff is the lasting mark of the crisis-era measure: a traffic signal could permit movement before green, but only by placing more responsibility on the driver to make the intersection safe.
