During these scenarios, traffic is managed by taking turns running cars in each direction on the same lane. You can do that with a couple of construction workers, walkie talkies, and stop signs ...

Cities employ these when the direction of travel on a lane changes ... because most all traffic signs that are side mounted — not over the lanes — would have the arrows pointed up,” Lindley ...

In 1947 he was called to Denver. In his first four years, he installed 30,000 traffic-direction signs along Denver streets, cut down big street-corner trees to improve visibility at intersections ...