A main road through Buckshaw Village has been closed for two weeks.
Lancashire County Council is replacing a crossing on Buckshaw Avenue to make it easier for pedestrians and cyclists to cross.
The work, which started today, will see the introduction of a straight crossing, rather than the current staggered crossing.
Buckshaw Avenue is closed at the crossing and diversions are in place for motorists.
But County Coun Mark Perks said: “Clearly this diversion is going to send all this traffic through what is a residential area.”
He said an alternative drop-off point would be in place next week for parents taking children to Trinity Buckshaw Primary School.
John Gatheral, highways design manager for Lancashire County Council, said: “The diversion keeps traffic to the larger through-routes, taking drivers north along Central Avenue, east then south on Old Worden Avenue, and then south on Village Way.
“This is the only route safe and suitable for HGVs and other large vehicles, though local drivers of light vehicles will no doubt be aware of and make use of more direct alternatives.”