May 16. By Dave Vieser. While many motorists express dismay about the pace of traffic crossing the Exit 28 DDI, the configuration is much safer than the traditional interchange it replaced. According to a new report prepared by the Cornelius Police there has been a 67% reduction in accidents at the Catawba Avenue/I-77 interchange since the Diverging Diamond Interchange (DDI) opened.
Injury accidents fell 91% during the same period. The DDI was constructed in 2014, so the new data compares accidents from 2013 to 2015, 2016, 2017, and 2018.
The traffic configuration was radical enough to turn Cornelius on its ear and launch a Facebook page, Exit 28 Ridiculousness. The description of the page then was edgy: “Take advantage of all the time you are stuck sitting at Exit 28 and document the absurdities.”
But police say there have not been any major incidents thus far involving the DDI.
Town and NCDOT officials attribute the improved safety record primarily to the reduction in the number of “conflict points” vs. a traditional interchange design. DDI motorists cross the interstate on the left, rather than the right side of the road, and then sort of bear left to enter the interstate. Eliminating the left turns is the primary advantage of the DDI.
During the study period, there was one fatal incident involving the DDI but after investigation it was determined that a medical condition, not the intersection design, contributed to the accident.
But there is still some concern over the ability of emergency vehicles to rapidly cross the bridge. The bridge is not wide enough for two cars and a fire truck to fit side by side.
FIRE CHIEF SMITH
“From a fire department perspective, the DDI leaves no room for cars to move or pull to the side while we are responding to calls,” said Cornelius Lemley Volunteer Fire Chief Neal Smith.
Drivers are hesitant to pull over toward the barriers or proceed into an intersection due to the configuration of the DDI and the traffic flow, Smith said.
“This has created slower response times for us whenever we have to cross the bridge,” Smith said.
Another issue is that the intersection does not have the ideal amount of distance between US 21 on the east and Torrence Chapel Road on the west.
Improvements are planned for both but they will still be closer to the bridge than ideal for traffic movement.
And then there’s the mast and sail design on the bridge. It hasn’t turned out to be the tourist magnet that former officials imagined. Planned instead is a modest tree and shrub design on the four quadrants of the bridge.
