Portions of a retaining wall alongside an unfinished section of the I-75 reversible Express Lanes near Windy Hill Road collapsed onto the roadway early Monday.

The unfinished roadway is still under construction and is not being used by traffic, so no vehicles were on the highway and no delays were expected.

The Georgia Department of Transportation did not have any immediate word as to the cause of the incident or what sort of delay this may add to the opening of the Northwest Corridor Express Lanes project, which was originally slated to open later this summer.

The project was designed to help relieve traffic along I-75 and I-575, by providing reversible toll express lanes that run southbound during the morning rush hours and northbound during the afternoon rush.

Retaining wall collapses on I-75 Express Lanes outside Atlanta

Motorists using the lanes would use the same type of Peach Pass transponders used by drivers in Peach Pass lanes on I-85 in Gwinnett County and on I-75 to the south of Atlanta.