Up to 10,000 bikers will be travelling on the M4 in Wiltshire on Sunday in support of the armed forces serving in Afghanistan.
The riders will be taking part in an organised ride from Hullavington Airfield to Wootton Bassett.
The Highways Agency said motorists would encounter increased traffic throughout the day especially around junctions 16 and 17.
The ride is expected to raise up to £50,000 for the Afghan Heroes charity.
Wiltshire Police Chief Inspector Owen Gillard said the force was working with the Ministry of Defence and Wiltshire Council to ensure public safety.
The idea for the ride, which is also to honour the people of Wootton Bassett, was suggested in a group set up on the social networking website Facebook.
Riders will congregate from 0800 GMT and the ride will start on the runway at Hullavington Airfield (A429) before proceeding to the A429 (north west to Burton Hill), B4042 (Priory Roundabout to Callows Cross), Callow Hill to White Hill Lane and the A3102 to Wootton Bassett.
The last riders are expected to arrive at Wootton Bassett at around 1800 GMT.
A police spokesman said there may be traffic delays throughout the day.
"Alternative routes should be found wherever possible," he said.
He added that temporary traffic lights will be in place two miles north of Junction 17 on the A429, near the entrance to Hullavington Airfield.