this depends on where the truck is registered and to what the laws are of that region.
Added: (in the US) Commercial vehicles engaged in interstate commerce must be equipped with splash guards by DOT and ICC regulation and according to most state laws. This is one of the many things that 'weigh stations' check for on interstate and US highways, which can be seen at the entrance to most states and at intervals throughout the state.
ADDED: Mudflaps are not regulated under the Federal Motor Carrier Safety Regulations, it is a State law in those states that require them.
Mud flaps have to be on medium and heavy duty trucks in Pennsylvania. This is the law and you can be fined if they aren't.
In Oregon they are Michigan requires Mudflaps (anti-splash devices) on commercial vehicles.
yes if it is on an 18 wheeler trailer or tractor
Yes.
are truck tractors required mud flaps
No
Buses and vehicles transporting hazardous materials are required to by law.
It is required by the law.
No. Florida wouldn't pass any such law unless it was passed as a part of the Federal Motor Carrier Safety Regulations first. As it, the FMSCR has no requirement for commercial vehicles to have air conditioning.
Illinois state law makes their use illegal only in commercial vehicles. However, the definition of a commercial vehicle under Illinois law may be more broad than the definition of commercial vehicles under the FMCSR, and may include vehicles not within the jurisdiction of the FMCSR, such as courier vans, taxi cabs, limousines, etc.
Because the bureaucrats who administer the law have no imagination
recommended but not required by law.