The Texas Department of Transportation has selected the intersection of MoPac and Slaughter Lane to be the site of the third diverging diamond interchange, or DDI, in Texas.[/caption]

After more than two years of research, the $45 million improvement project to alleviate traffic at the MoPac and Slaughter Lane and MoPac and La Crosse Avenue intersections is moving forward now that its environmental study has been completed.

The study began in May 2013. The Texas Department of Transportation issued a Finding of No Significant Impact regarding the MoPac Intersections Environmental Study on Dec. 22.

TxDOT is now working on the final design, which leads to construction in the spring, TxDOT spokesperson Kelli Reyna said. Construction is expected to take two or three years.

Revising the intersections

The project involves three components: the construction of four main MoPac lanes that pass under Slaughter and La Crosse, a traditional diamond intersection overpass at MoPac and La Crosse, and a new style of overpass at Slaughter and MoPac known as a diverging diamond interchange, or DDI.

Currently, the Slaughter and La Crosse intersections use traffic signals, causing MoPac drivers to stop at each crossing.

“[The traffic signals] are where a lot of the backup comes from, especially in this particular area because everyone is forced to go through that traffic signal,” Reyna said. “The difference with this improvement project is that the MoPac main lanes will go underneath these two new bridges.”

A new type of intersection

The DDI involves drivers wishing to make a left turn temporarily traveling on the left side of the road, which allows for through-traffic and left-turn drivers to proceed at the same time, Reyna said. The only time drivers will be on the left side of the road will be on the overpass section of the DDI, she added.

To navigate the new style of intersection, Reyna said drivers should follow all road signs and markings and follow the traffic flow to safely navigate.

The DDI will be the first of its kind in Austin and the third in Texas, Reyna said. The other two DDIs are located in Round Rock and El Paso.

“One of the reasons why we are going towards these types of innovative intersections [is] because we are able to do more with less,” Reyna said. “They are relatively low- cost improvements that have great traffic benefits. You are able to move a large amount of traffic through seemingly the same surface area as a traditional intersection.”

According to TxDOT, MoPac south of Cesar Chavez Street handles 130,000 vehicles per day.

 For Southwest Austin resident Ramon Noches, who has lived in the area for 27 years, the changes are welcome. Noches called for urgency in starting construction.

Noches said he was also in favor of the overpasses, saying their construction can help to prevent the traffic crashes at the intersections.

“The [DDI] is more complex than what I am used to, but it is needed,” Noches said.