Innovative Intersection Designs

Innovative Design Solution for MoPac/Slaughter Lane Intersection

TxDOT has constructed an innovative, long-term solution for traffic congestion at MoPac and Slaughter Lane. The solution involves separating the north-south traffic on MoPac from east-west traffic on Slaughter Lane using what is called a Diverging Diamond Intersection, or DDI.

This video shows an example of a DDI. The application of a DDI at a specific location may vary in configuration and operations.

The design reflects public comments and stakeholders suggestions for a solution that would minimize traffic noise and visual impacts while making it faster and safer for motorists, cyclists and pedestrians to get through the intersection.

The DDI shifts traffic approaching the intersection to the left, then back to the right after the intersection to allow drivers who want to turn left to keep moving and reduce the number of traffic signal intervals. A key advantage of the DDI is the reduced wait time for traffic making a left turn.

This innovative intersection is being implemented in Central Texas today at RM 1431 in Round Rock.

Other advantages of the system:

• No additional right-of-way is needed (current and planned businesses on each corner of the intersection would remain and not have to be taken).
• No changes in access for Slaughter Lane businesses (Taco Bueno, Walgreens Drug Store, Chase Bank, Wendy's, etc.).
• Pedestrians have safe east-west crosswalks.
• Cyclists have a dedicated bike lane across Slaughter Lane for a safe east-west connection.
• At an estimated $15 million, the solution is a cost-effective way of addressing traffic needs for the long term.

So how well will the DDI with grade separation work 20 years from now? Modeling results show that morning rush hour traffic would have an average wait time per vehicle of about 17 to 41 seconds, and evening rush hour traffic would have an average wait time per vehicle of about 19 to 26 seconds.

Please download: FEBRUARY 2015 DDI FACT SHEET

Design Solution for MoPac/La Crosse Intersection

At La Crosse Avenue, the project will build a conventional intersection, similar to most intersections in the area.