Emergency services were alerted of the incident yesterday around 5.20pm at Stamperland Crescent at Clarkston Toll Roundabout.
An 86-year-old man was struck by a Mercedes GLE and rushed to Queen Elizabeth University Hospital, where his condition is critical.
The driver, 54, was uninjured.
Cops closed the road for hours for the investigation, but it has now reopened.
Detectives are asking anyone with information to get in touch.
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Seargeant Scott Gourlay said: “I would like to appeal to anyone who was in the area, who has not yet spoken to police, to contact us.
“If anyone has a dash cam, please pass on any relevant footage to us as it could assist us in establishing the full circumstances of this incident.”
Anyone with information is asked to call Police Scotland via 101, quoting incident number 3034 of 17 May, 2024.
