Officers would like to speak to anyone who saw an incident at junction one of the M621 between the slip roads at about 9.25am on Monday, October 15.
It took place after a black Suzuki Swift and a white Vauxhall Corsa crashed in lane two of the motorway.
A Vauxhall Corsa braked suddenly just before the crash after a silver car pulled in front of it and braked hard.
The female driver of the Corsa suffered minor injuries and was taken to Leeds General Infirmary, police said.
Anyone who saw the collision or the driving of the silver car before the collision, or has dashcam footage, is asked to contact PC Andrew Senior at the Safer Roads and Neighbourhood Support Team on 101 referencing police log 0405 of October 15.
Information can also be given online via 101 Livechat at https://www.westyorkshire.police.uk/101LiveChat