Coming to an Intersection Near You
SPUI helps control heavy traffic
Diamonds may be forever but not necessarily when it comes to traffic interchanges.
In Utah, Florida and Michigan, highway engineers are replacing the traditional diamond interchange with a single-point urban interchange, known as SPUI. SPUIs can handle heavier flows of traffic--between 1,500 and 5,500 vehicles per hour--by allowing cars diagonal from each other to make left turns at the same time, and are especially effective where traffic is equally heavy in both directions. "Operationally, they are more simple," says Mack Christensen, of the Utah department of transportation. "You eliminate one signal, which allows you to control traffic at one point. Therefore, you reduce the number of conflicts and phases."
SPUIs also take up less space than a traditional diamond interchange: Diamond interchanges require about 1,200 feet of right-of-way space, while SPUIs only need 250 feet.
But there are some problems with the new configuration. Drivers may be confused when they make a left turn and find that cars coming from the opposite direction are also making a left turn--on their right side. A SPUI is also more expensive to build than a diamond interchange--usually by 30 percent to 50 percent, depending on terrain and existing infrastructure. The greater cost of a SPUI can sometimes be offset by not having to purchase as much land since its requires less space.
Join the Discussion
After you comment, click Post. You can enter an anonymous Display Name or connect to a social profile.
LATEST INFRASTRUCTURE & ENVIRONMENT HEADLINES
Texas High Court Strikes Down Houston's Air Pollution Rules14 hours ago
The Miami Method for Zoning: Consistency Over Chaos1 day ago
Remembering Cincinnati’s Old Streetcars1 day ago
The Secret to a Successful Bike Share1 day ago
U.S. Transportation Secretary Replaces 3 D.C. Metro Board Members3 days ago
Massachusetts’ Unlikely Transit Team4 days ago