Your question has no answer - WHY?
Coach companies do not record the number of hours driven by their drivers nor the number of passengers carried during that time so how can there be a comparison. There are no records of the number of hours driven by car drivers nor the number of car occupants during their journeys. Same problem for taxi drivers and boats/cruise liners. Cyclists do not keep records.
I do not know the answer but would expect that cyclists, both pedal and engine powered are in one of the highest risk areas but where all the other travellers by mechanised forms of transport stand is anybodies guess. Coach travel seems pretty risky to me seeing that the roll-over surviveability of coaches is nigh on nil. They don't seem to have any safety requirements, like cars, boats and aircraft. But maybe they do.
So basically Your question is a matter of guess work and speculation.