Emergency services attended the scene on Downall Green road between junction 24 and 25 of the M6, shortly before 1.15pm on November 22.
The woman was taken to hospital with serious injuries, however it is not known if they are life-threatening.
The Wigan motorway was closed in both directions for over an hour but has since re-opened.
A spokesperson for Greater Manchester Police said: "Inquiries are ongoing.
"Anyone with dashcam footage from the area at the time is also asked to get in contact with police.".
Information can be reported online at www.gmp.police.uk quoting log 1303 of 22/11/2021. Alternatively, contact Crimestoppers anonymously on 0800 555 111.
Thanks for reading. If you value what we do and are able to support us, a digital subscription is just £1 for your first month. Try us today by clicking here