Raleigh, N.C. — The North Carolina Department of Transportation originally said the contractor working on the I-40/440 Rebuild – the massive project to rebuild an 11.5-mile stretch of Interstates 40 and 440 – would need to keep at least two lanes open in both directions along the roadway when construction begins in January.
But when traffic engineers at North Carolina State University plugged that into a model, it wasn't pretty.
“We actually would have predicted a 10-fold increase in travel time,” said Bastian Schroeder of N.C. State’s Institute for Transportation Research and Education
The model predicted that backups in the evening would start on I-40 eastbound around Airport Boulevard and continue all the way through the work zone.
But the contractor, Granite Construction, says it can keep three lanes open, which would confine delays mostly to the work zone.
With three lanes open, the model shows the impact on traffic is much less severe.
Now, the typical travel time for either direction on I-40 between Airport Boulevard and N.C. Highway 42 is about 27 minutes.
Assuming three lanes are open and 20 percent of drivers would choose an alternate route, the model shows the morning commute on westbound I-40 from N.C. 42 to Airport Boulevard would take about 38 minutes.
The model says the evening commute would be the toughest – eastbound I-40 would take an estimated 55 minutes.
The morning commute may be worse on alternate routes. According to the model, travel times on routes such as U.S. Highway 70 Business, Hammond Road and Rock Quarry Road could increase at least 30 percent.
Schroeder says this model data is a worst-case scenario. The contractor says it won't build in the entire work zone at once. It will complete the project in phases, which will help with congestion.
The models also don't take into account telecommuting and carpooling, which would reduce congestion.
“If we get everybody to carpool, then things will be better than they are today or at least the same as they are today,” Schroeder said.
Schroeder and his colleagues are working on new model data to determine the impact of the contractor's plan to work in stages.