"This animation shows a Single Point Urban Interchange that links a major thoroughfare, or arterial street, on top with a freeway that passes underneath. The name, Single Point, refers to the fact that all thru-traffic turning left onto or off of the interchange can be controlled from a single set of traffic signals. In this example, all traffic signals are located at a single point in the middle of the interchange.

There are three traffic signal cycles. The first cycle is for thru-traffic that is not turning. Cycle two is for traffic leaving the freeway, entering left onto the arterial street. Cycle three is for traffic leaving the arterial street and turning left onto the freeway.

You've just seen how a Single Point Urban Interchange works."