The ISDT (International 6 Day Trial) etc was held on public roads, first run just prewar WW1, until 1981.
When it was renamed ISD Enduro, and held off road.
Many of the 'Trials' pre 1981 were road events for road bikes, and could cover 200 or 300 miles a day, usually on what were termed B roads or less, and kept to a strict time timetable, and tests for changing a tyre or a plug etc in very strict time limits. Also on what could be changed on the machine without being disqualified.
Not to be mixed up with pukka trials events where creeks and hills and tight turns and cliffs and rocks came into it, and putting a foot down cost a point.
No idea how you distinguish these 2 types of events from each other...