"There's a real challenge in deciding what constitutes work," said Dr Jain, from the university's Centre for Transport and Society.
"Work" is anything I would be doing while sitting at my desk in your office building. So if I'm doing that on a train or in your office they are both "work." And if my train ride takes 1.5 hours to the office and 1.5 hours home, I'll get on the train around 8AM and leave the office at 3:30 to arrive at the other end by 5PM and count that as an 8 hour work day.
On the other hand, if I am in my car driving, I don't think of it as work until I can actually concentrate on doing work.