Here a link to
Certification Specifications and Guidance Material for Commercial Air Transport by Aeroplane — Scheduled and Charter Operations, CS-FTL.1, Initial Issue 31 January 2014
GM1 CS FTL.1.200 Home base
TRAVELLING TIME
Crew members should consider making arrangements for temporary accommodation closer to their home base if the travelling time from their residence to their home base usually exceeds 90 minutes.
It does NOT define how the time is spent during the 90 minutes travelling time, so it could be by air... Open to interpretation...