A family up here accidently gassed themselves a few years back by this means. Nice modern house, too. The fire danger of a vehicle used to be much greater but still a stand alone garage would be better just in case.
A few years ago I watched a 3500 SF house on a hill in San Ramon burn to the ground in less than 40 minutes due to a garage fire initially caused by a faulty horn relay in the brand new Caddillac with full tank parked therein.