It happened on the M1 at Wakefield at about 6.50pm on Christmas Day.
A blue Vauxhall Zafira people carrier that was travelling on the southbound M1 between junctions 40 and 39 crashed with the central reservation and came to rest in the carriageway.
A woman got out of the Zafira and was hit by a grey Vauxhall Astra travelling in the same direction.
The woman, aged 50, from Wakefield, was seriously injured.
She is continuing to receive treatment in Leeds General Infirmary.
A 48-year-old man from the Zafira was arrested at the scene on suspicion of drink driving.
He was later released under investigation.
The driver of the Astra was interviewed by voluntary attendance.
Anyone who witnessed the incident is asked to contact West Yorkshire Police Roads Policing Unit via 101 quoting log number 1074 of December 25 or online via www.westyorkshire.police.uk/101livechat.