I wouldn't have thought it was legal to use a machine of any kind in a moving vehicle. I do know you are not allowed to even sit in a caravan while travelling.
A sewing machine even a hand crank would not be safe in a moving vehicle incase of an emergency stop etc. it would become a flying object.
Hand work or pinning ready for sewing I. The evening would be my best suggestion, can you imagine the picture sewing machine sitting on the steering wheel as you travel along the roads. It would be easier to be a pilot and put it on auto.