Drivers experienced rush-hour tail-backs this morning.
The roadworks on the A630 Balby Road also caused traffic problems on other main routes into town.
The first phase of works - which will include a bus lane - includes the closure of in-bound and out-bound lanes and is expected to last for several weeks.
The works are to ease congestion on the route used by 44,000 motorists a day.
For latest information go to www.smartroutes.co.uk/a630.