No a bus is not a truck.

Truck-Bodies is a blog that gives information on service trucks and the truck bodies they use. Truckers can communicate and collaborate about their mutual job connection.

Since momentum equals mass times velocity, if the mass of the truck times its velocity is greater than the mass of the bus times the bus' velocity then the momentum of the truck will be greater than the momentum of the bus.

A commmercial vehicle is a truck or bus that is bigger in weight than a car. (ex. school bus, 18 wheel truck)

There are many companies manufacture truck bodies. That include: "Watkins Manufacturing Inc", "Mclellan Equipment, Iinc", "Monroe Service Bodies", "JOMAC Ltd."