A 77-year-old woman and her son were seriously hurt when a quad bike apparently went out of control and struck them on the pavement.
The incident happened at 3-20pm on Thursday afternoon on Manchester Road, Nelson, and police are appealing for witnesses.
The woman and her son - who is in his fifties - are from Nelson. They were walking along Manchester Road towards the town centre when they were struck by the quad bike which mounted the pavement.
They both suffered serious injuries but they are not thought to be life-threatening. They were taken to Royal Blackburn Hospital in separate ambulances. One went rapidly through the town centre with blue lights and sirens on to take the victim to the motorway and Blackburn.
The rider of the quad bike suffered minor injuries.
A 23-year-old man - possibly from the Burnley area - who is thought to have been riding the quad bike was arrested and asked to help police with inquiries.
Sgt Malcolm Bell of the Road Policing Unit said: “We would like to make a witness appeal.” He said that there were possibly hundreds of people around the scene when it happened, but only two witnesses had come forward.
Anyone who was a witness is asked to contact the police by calling 101, or contact Crimestoppers anonymously on 0800 555111.
Manchester Road was closed between Lomeshaye Road and the edge of the town centre for around two and a half hours, and as a result there were traffic problems, especially during the rushhour.
There were cars queued up right along to the motorway roundabout at Brierfield.