A driver who was killed when his Land Rover Discovery crashed into a tree was a Special Constable with Sussex Police.
He has been named as Michael Arnold, from Crawley.
The force has paid tribute to a "long-standing and highly-regarded member of the police family".
A spokeswoman said: "He was a loyal member of our team having developed a wide range of experiences during his 11 years' service, from major incidents to local policing action.
"He will be sorely missed and it will be a long time before there is anyone who will be able to come close to the Special Constable that was Michael."
Mr Arnold died on Friday last week when his car left the A23 Brighton-London road at Hickstead.
His funeral is being held at 1pm on Friday at St John's Church, High Street, Crawley.
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