Where my dealership is we have to drive a fair bit to get out of the towns and onto a open road....you do a round trip and it comes to about 14mile. If you then need a 2nd opinon then your gonna have to go do the same again.....so 30mile for a road test seems fine imo. The customer would be alot more fucked off if they had to keep on returning for the same fault when it could have been diagnosed in one decent road test and sorted wouldnt they.