Drivers in Springfield, Missouri are trying out the new diverging diamond interchange:
When a driver on the four-lane Kansas Expressway reaches the interchange, his two-lane path goes over a bridge spanning the interstate. There are stoplights for north- and southbound traffic at both ends of the bridge.
Passing through the first stoplight, traffic crosses over to the left side of the bridge. And at the stoplight on the other end of the bridge, cars cross back over to the right, returning everyone to the right side of the road.
Drivers wanting to get on the interstate no longer have to wait for a left-turn signal; they veer left as they cross the bridge, with no cross-traffic.
The whole thing’s cheap, too:
Saiko says that’s because the change doesn’t require much new construction. “We’re using the existing bridge, didn’t have to replace the bridge, so that’s a huge savings,” Saiko said. “If we would’ve had to replace the bridge, it would have been around $10 million — and this project was just around $3 [million].”
If time is money, consider that it took less than half a year to build the new interchange in Missouri. With traditional designs, construction can drag on for two years.