Cars,those urban monstrosities the vehicles that weigh over 25 times their payload and take up 20 times the space on the roads. Should I adjust the figures for

Cars,those urban monstrosities the vehicles that weigh over 25 times their payload and take up 20 times the space on the roads. Should I adjust the figures for American sizes? Should I also add that they are engineered to travel at speeds over 120 mph and usually ply the trade environments where 30 mph is a dangerous speed?