A single-point urban interchange (SPUI) is an intersection design that allows a large volume of vehicles to travel through the intersection safely and efficiently by reducing conflict points and the number of traffic signal phases. Similar to a diverging diamond interchange (DDI), the SPUI allows opposing left turns to proceed simultaneously. Unlike a DDI, streams of left-turning traffic in a SPUI are not shifted to the opposite side of the roadway. Opposing left turns can be made at the same time; with only one set of traffic signals, allowing more vehicles to clear the intersection in one traffic signal cycle.
Benefits of a SPUI include:
- Improved safety: With only one signalized intersection rather than two at a conventional diamond interchange, vehicles only cross paths at one location.
- Improved travel time: Additional "green time" at traffic signals allows more vehicles to pass through the intersection.
- Wider turns for large vehicles.
- Reduced right-of-way requirements.
A SPUI is being considered for the intersection of I-35 at SH 29.
Watch the SPUI explanatory video to see how it works. You can also read the SPUI fact sheet to learn more.
The first phase involves cross-street traffic traveling through the intersection.
The second movement is for the second set of opposing left-turn lanes traveling from the cross street onto the frontage road.
The last movement involves opposing left-turn lanes from the frontage road and/or exit traveling through the traffic signal onto the cross street. Through traffic on the frontage road is handled via intersection bypass lanes in both directions.