The incident caused long morning rush hour delays on the M65 between heading Preston and Blackburn on Thursday, September 14.
Two lanes of the motorway between junction three at Wheelton and four, at Darwen, were shut for three hours while emergency services and accident investigators dealt with the crash between a lorry and a van.
A Renault Box van and the lorry collided around 8.45am.
The driver of the van, a 37-year-old man from Wigan, was taken to Royal Preston Hospital with a serious break to his right leg.
A passenger in the van, a 24-year-old man from Atherton, suffered a neck injury, which is not thought to be serious.
The driver of the HGV, a 34-year-old man from Barking, London, was uninjured.
Lancashire Police would like to speak to anyone who may have seen what happened or might have dashcam footage.
Sergeant Claire Pearson of the Roads Policing Unit said: “We are trying to piece together exactly what occurred and would like to hear from anybody who saw the collision or saw either of the vehicles in the moments beforehand.
“If you have any information that could help with our investigation, we ask that you get in touch as soon as possible.”
Anybody with information is asked to email [email protected] or call 101, quoting log number 239 of September 14.