The days of trucks smashing into the Hay Street overpass could be over as works get underway this weekend to increase the clearance of the bridge over the Mitchell Freeway.

The Mitchell Freeway southbound will be closed from the Graham Farmer Freeway off-ramp this weekend between 8pm Friday and 2am Monday as the works get underway.

The following weekend, the WA Day long weekend, works will extend into the Monday public holiday as the closures run from 8pm Friday May 29th to 2pm Monday June 1st.

Director of metropolitan operations at Main Roads Peter Sewell said those planning to head down south for the long weekend should plan ahead and factor in detours.