Roads other than the Interstates are regulated by the individual states, and laws vary widely. Maximum weight varies between to , depending on the combination. Most states restrict operation of larger tandem trailer setups such as triple units, turnpike doubles and Rocky-Mountain doubles. Reasons for limiting the legal trailer configurations include both safety concerns and the impracticality of designing and constructing roads that can accommodate the larger wheelbase of these vehicles and the larger minimum turning radii associated with them. In general, these configurations are restricted to the Interstates. Except for these units, double setups are not restricted to certain roads any more than a single setup. They are also not restricted by weather conditions or "difficulty of operation". The Canadian province of Ontario, however, does have weather-related operating restrictions for larger tandem trailer setups.