High-speed trains often move close to straight-line (which is a reason why they're so expensive) and if you compare to planes (for longer distances), they also

High-speed trains often move close to straight-line (which is a reason why they're so expensive) and if you compare to planes (for longer distances), they also fly approx straight lines. Theoretical average speed is a valid measurement, in my opinion, also for door-to-door times for flying vs. driving.