I notice you have conveniently failed to mention 'getting to and from stations, waiting around at stations, etc'.
Either you compare brakes off to brakes on for both modes, or door-to-door for both modes.
Taking my Edinburgh-London example, it would take me 5 minutes to reach Waverley station, 10 minutes waiting around, then a 5-minute walk from Kings Cross.
So, doorstep to doorstep Edinburgh-London will take me around 4 hours 50 minutes.