The changeover was announced last fall partly as a response to noise complaints from residents of suburban neighborhoods along the loop. Those residents were reeling from the high-volume traffic noise of interstates 40 and 73 bound for a merger near Groometown Road with I-85.

But noise reduction was only a small part of the reason for DOT's decision to resurrect I-40's original route, Eason said.

The larger motivation was financial, Eason said. Putting the two interstates on the same route had cost DOT $3 million a year in maintenance money from the federal government, which awards that money based on the number of miles of interstate highway in each state.

In addition, many motorists were complaining to DOT that they found it confusing to maneuver onto the loop, Eason said.

When they announced plans in September to peel I-40 traffic off the new section of the loop, DOT officials said they had studied the original route in depth to make sure it could handle the rerouting safely.