Major delays were predicted on the M61 on Wednesday evening after a crash closed the northbound motorway.
A woman motorcyclist was taken to Royal Preston Hospital with serious injuries and two male drivers were taken to Chorley Hospital with minor injuries.
Five vehicles were involved in the crash during rush hour close to junction eight, at Chorley, Lancashire.
All lanes between junctions six, at Horwich, Greater Manchester, and eight were closed, but one has re-opened.
Police warned of "considerable congestion" as far back as junction five, in Westhoughton, Greater Manchester.
It was estimated the tailbacks would take several hours to clear.
Traffic was being diverted via the A6.