Subject to all other speed restrictions of this chapter no person shall drive a vehicle not designed for carrying passengers and equipped with pneumatic tires at a speed in excess of:

1. (1) Twenty miles per hour in any business district;
2. (2) Twenty-five miles per hour in any residence district;
3. (3) Forty miles per hour on open country highway;
4. (4) Trucks licensed at eight thousand pounds gross vehicle weight or less shall be permitted the same speed as passenger cars.