"Passenger van" means any van or other motor vehicle owned by any agency, business or other legal entity and operated for the purpose of transportation of children under the age of eighteen years, other than a van utilized for private use, taxicab, bus or school bus. Passenger vans include, but are not limited to, vehicles used by day-care centers, after-school centers and nursery schools: Provided, That the term "passenger van" does not include any van or other motor vehicle which is utilized for the specific purpose of transporting children to medical facilities for the purpose of medical or dental treatment and which loads and unloads the children on private property, making no stops for loading or unloading along public roads or highways.