The 55 mph speed limit began with a war on the other side of the world.
In 1973, during the Arab-Israeli war, Arab oil exporters cut shipments to the United States over its support for Israel. Prices spiked. Drivers waited in lines outside gas stations.
Washington reached for conservation: the speed limit first, fuel-economy standards for new cars later.
The shock didn't invent energy policy. It means saving fuel stopped being thrift and became defense.