Pedestrians and motorists have been warned that William St rail crossing in Lurgan will be closed all weekend.
The closure is to facilitate a £25m upgrade by Translink to the rail line.
The crossing is on one of the main arterial routes into Lurgan and is normally extremely busy.
A complete closure of the crossing will mean pedestrians as well as motorists will have to take an alternative route.
A footbridge over the railway line toria Street will be open to pedestrians.
Police have urged patience while the essential work is being carried out over the weekend.
PSNI Craigavon said: “Think of it as short term pain for long term...slightly less pain.
“The foot bridge will be open for pedestrians, and Brownlow Terrace - Victoria Place footbridge is still there.
“If you are headed between town centre and motorway, use Kiln Road, Francis Street, Edward Street.
“Please remember the road will be totally closed, so no amount of “but I just live down there...” will get you through. You’ll have to go round, as we will too!
“There will be a bus substitution in place over the weekend for those mad enough to want to leave Lovely Lurgan.
“Please be patient, and plan your journey accordingly!”