New Diverging Diamond Interchange to open in Westmoreland County
Starting Tuesday morning around 6 a.m., where Interstate 70 and Route 51 meet in Rostraver Township, a new traffic pattern, a Diverging Diamond Interchange, will emerge.
PennDOT is asking drivers to have a little patience and to plan their trips accordingly in and around the interchange, and they are asking people to slow down and stay alert.
"What's going to happen tomorrow is we are going to split it. We have had traffic on both sides of the road, we are going to split it," said Dominec Caruso, the assistant construction engineer for PennDOT's District 12. "It is still going to maintain a single lane configuration that is going to put traffic on both outside edges and allow us to finish the median portion of the road. And tomorrow, we will also utilize all of the ramp. So, we will now be going into the Diverging Diamond situation where you are going to cross traffic into the opposing lanes to facilitate those movements."
The Diverging Diamond Interchange, or DDI, may sound complicated, but PennDOT is trying to alleviate drivers' concerns, adding that it is meant to move traffic more efficiently compared to the old clover-style interchange.
"The DDI design permits smoother traffic flow on and off of I-70 by moving Route 51 traffic to opposite sides of the interchange, and traffic can directly access the entrance ramps without stopping at signals," according to a PennDOT traffic video.
This style of interchange has become popular both nationally and locally, with the first DDI in the state being created in Washington County a few years ago.
PennDOT says that DDI is not only a more efficient traffic pattern, but it can also be safer.
"When you switch the traffic onto the left side of the road, it eliminates conflict points with the opposing traffic by up to 50%," Caruso said. "Minimizing those left turns, across traffic, reduces the number of accidents you can have, and it also reduces the severity of the accident you can have. You can have, typically, no longer head-on collisions or T-boning situations."
This new interchange and traffic pattern is only part of an ongoing construction project. Construction in this area is slated to wrap up sometime in the fall of 2026.
