Trucks and heavy traffic will be diverted from the Northern Distributor Road, near Orange, for a week from Friday.
Part of the road will be closed for repairs.
Traffic heading to Bathurst and beyond (and in the opposite direction to Wellington and Dubbo) will be diverted to Summer Street and through the Orange city centre and on along the Mitchell Highway.
Heavy traffic will also be re-routed down William Street next Tuesday to allow Anzac Day services to go ahead in Robertson Park and Summer Street.
Orange City Council’s infrastructure committee chair Councillor Glenn Taylor said a two kilometre section of the bypass between Bathurst Road and Icely Road had to be closed to allow for a specialised seal to set and cure.
Cr Taylor said contractors were ripping up the top 300 millimetres of the road to add the new surface.
They were also adding drainage channels on both sides of the road to help clear water.
The bypass opened in August 2012 but has received criticism over its deteriorating condition.
Electronic message boards will be placed on roads leading into Orange to alert motorists of the closure.