A Mitsubishi people carrier has been badly damaged in the smash, which has occurred near the junction with Player Street.
2 Fire Appliances from Ryde are on scene alongside the Isle of Wight Ambulance Service and Police.
The driver, who is understood to be in a potentially life-threatening condition, is being rushed to St Mary’s Hospital, Newport.
It remains unclear as to whether or not a medical episode is behind the cause of the crash.
The road is closed in both directions as emergency services deal with the incident.
UPDATE @ 12:16 – The area has been cordoned off by Police as officers await news from St Mary’s Hospital.
Traffic is being diverted locally using Player Street, Warwick Street and Park Road.
Firefighters have now left the scene and returned to station.
UPDATE @ 14:10 – The driver of the vehicle, an elderly man, is in a serious condition in hospital this afternoon. Doctors are conducting a CT scan on the gentleman to ascertain the best way forward.
It is understood the man suffered a medical episode at the wheel, veering off to the left before crashing into the corner of a building.
The specialist Collision Investigation Unit is now in attendance at St John’s Road where Officers from the mainland are working to document the scene and piece together the events of the crash.
The road remains closed.
UPDATE @ 17:28 – The car has now been recovered and the road has re-opened.
UPDATE @ 21:50 – Sadly, it has been confirmed by the gentleman’s family that the much-loved grandfather passed away earlier today.
A file is being prepared for the coroner.