There is no such thing as modified for the physically disabled person.The car is a normal car, but it is fitted with hand control unit.Any one can buy the hand control and a mechanic will install it on the car . That is the only modification I know of as I too drive one. On that basis it is highly unlikely that it will carry any duty exemption. I have driven hand control fitted cars both in USA and Australia as I am dual citizen in both those places hence I say this with hands-on experience so trust me ! This may well be a belated response but we'll worth hence I am compelled to clear any myths about hand control fitted cars.