COPENHAGEN — Like other Danes of a certain age, Iver Høj Nielsen clearly recalls the 1970s Arab oil embargo that plunged his Scandinavian country into an energy crisis.

Lines stretched for blocks near gas stations in this capital city. There were calls to keep the lights off in buildings. Most vividly, Nielsen says, he remembers taking quiet walks down empty streets on Sundays — when a driving ban kept cars and trucks from rumbling to and fro.

— Texas Tribune