The man was making his way down the "fast lane" on the A4119 in Llantrisant by mistake, South Wales Police said.
Officers arrived and made sure the area was safe following the incident on Saturday evening.
The man was taken to Royal Glamorgan Hospital for treatment, police said.
A man in an electric wheelchair was stopped by police after being spotted on a dual carriageway in Rhondda Cynon Taff.