Police have named the motorcyclist who died in a collision on the Mountain Road on Monday afternoon.
He was 59 year old Alan Ronald Osborne from Rochester, Kent.
According to police, Mr Osborne was riding a yellow and black Suzuki motorcycle which was in collision with a black Peugeot 206 and a white Fiat Ducato van, which was towing a trailer.
Officers say there has been a good response to appeals for witnesses, and they now want to speak to the rider of a red motorbike seen travelling towards Douglas just before the collision.
The rider may have been wearing a red helmet.
Visitors told "take extra care" as TT Fan Park to reopen
Sidecars have 'been my life', says Lambert
Road conditions 'atrocious', say police
Glover - Southern 100 sidecar suspension felt 'completely inevitable'
Vicar: "Everybody goes through compromise when it comes to the races"