October 11th, 2011

A RETRO DDI

Optimize Mobility, by Catherine Higgins.

A Diverging Diamond Interchange and Auxiliary Lane project will improve mobility and safety at the Bangerter Highway, SR-201 intersection.

The DDI intersection made its Utah debut in American Fork with the  Pioneer Crossing project. Now, UDOT is using the innovative design to improve traffic flow at Bangerter Highway and SR-201.

In addition to the DDI, the project will also add a traffic lane between Bangerter Highway and I-215, dual right-turn lanes onto the SR-201 eastbound on-ramp, dual northbound left-turn lanes on Bangerter highway at 1820 South and dual eastbound left-turn lanes at 2100 South Frontage Road to northbound Bangerter Highway. Together, the new intersection and lanes will reduce delay through the intersection and along the intersecting corridors in the area.

Reducing delay

DDIs reduce delay by eliminating left turn signal phases. In typical diamond intersections, through-traffic waits for left turning traffic accessing on and off-ramps. Without a left-turn phase, through traffic can proceed without waiting for left turning vehicles.

A DDI also eliminates the need for signals at the on and off-ramps. Vehicles using the ramps have free right and left turns and simply wait for a gap in traffic.

Since traffic patterns vary depending on location, traffic analysis must always be done to make sure a DDI is the best choice.  Studies show that the DDI is a good fit for this location.

A cost effective choice

In addition to supporting better mobility and safety, the DDI is also a good cost saving project at this location. Because the existing bridge has adequate space, UDOT is rehabilitating the bridge deck and adding striping and signals for the conversion.

The DDI project is part of UDOT’s Bangerter Highway 2.0 , an expansive upgrade that includes improvements from the Salt Lake City Airport to 13400 South. The effort will reduce travel delay on Bangerter Highway by incorporating the latest innovations in transportation mobility.

Ultimately, the project will achieve all four of UDOT’s  strategic goals known as the “Final Four”: Take Care of What We Have, Make the System Work Better, Improve Safety and Increase Capacity.

 

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