The M65 was closed near Brierfield after a three-car accident at 5.20pm.
There was queueing traffic on the eastbound carriageway between junction 11, Burnley centre, and junction 12, Brierfield.
Tailbacks were reported back to Junction 10 because no traffic was able to pass the accident heading towards Nelson.
Traffic was also queueing on the westbound carriageway.
Motorway police said drivers turned and drove the wrong way up the slip road and had to be stopped by police.