Officers were called to Bagwell Lane in Winchfield, Hampshire, this morning after a member of public found the man's body.
A Hampshire Police spokesman said there was no evidence of a collision and appealed for witnesses to help them establish what happened.
He said: "Police are investigating following the sudden death of a 60-year-old man from Basingstoke in Winchfield, near to Odiham, early this morning.
"At 08.12am a report was made to Hampshire Constabulary that his body had been discovered at the side of the road on Bagwell Lane. A tricycle, which it is believed that the man was riding, was also found.
"Initial inquiries do not indicate that the man or his tricycle were involved in a collision with another vehicle, or that anyone else was involved. Officers are, however, keen to establish the exact circumstances of what happened."