Avon & Somerset Police are appealing for spectators with video or photos of the fatal accident to contact them.
The crash happened as 23-year-old cyclist Junior Heffernan came round a bend during the Severn Bridge Road Race.
Here is Acting Inspector Darren Jarvis...
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Wiltshire Police have announced a crackdown on uninsured drivers this week. They say 1 in 100 vehicles driven in the county are uninsured.
It will be a breezy start, with clouds arriving around lunchtime. The afternoon will be sunny with showers.
Tuesday will start dry and bright with lighter winds, before cloud thickens bringing some outbreaks of rain through the afternoon.