The crash happened on the A6 approaching the hill down towards the bus station at around 5.30am.
The one-way road was closed by police with officers diverting traffic down Church Street until 9am.
Police have now opened one lane to alleviate some of the congestion and they are asking motorists to reduce their speed in the area whilst work takes place in the road to repair the crash scene.
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Details on any casualties is not known at this stage, but Lancashire Police and North West Ambulance Service have been approached for further details.
Earlier this morning, a police spokesman said: "There has been a RTC on the A6 in Lancaster city centre near to the junction of Damside Street.
"The road is completely blocked and is closed. Traffic is being diverted down Church Street.
"Please avoid the one way system. Large vehicles will not be able to get through the diversion."
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