(c) No vehicle of four wheels or less whose gross weight with load is over 24,000 pounds is permitted to operate over or along a public highway. Any vehicle having a greater weight than 22,400 pounds on one axle, or any vehicle having a combined weight of 800 pounds per inch-width of tire concentrated upon the surface of the highway (said width of tire in the case of solid rubber tires to be measured between the flanges of the rim) is also barred by the provisions of this law, with the following exception: PROVIDED, that in special cases vehicles whose weight including loads whose weight exceeds those herein prescribed, may operate under special written permits, which must be first obtained and under such terms and conditions as to time, route, equipment, speed and otherwise as shall be determined by the director of licenses if it is desired to use a state highway; the county commissioners, if it is desired to use a county road; the city or town council, if it is desired to use a city or town street; from each of which officer or officers such permit shall be obtained in the respective cases. Provided, that no motor truck or trailer shall be driven over or on a public highway with a load exceeding the licensed capacity. _Chain Drive._ Trucks equipped with a chain drive should be supplied with an extra set of chains so that they may be changed and cleaned every week. To clean the chains, they should be soaked in kerosene which removes the dirt, grease and gum that has accumulated. By doing this the life of the chains will be quadrupled. The small amount of time that it takes will pay. _Top._ The truck should come equipped with a top over the driver's seat that is easily detachable. In bad weather the driver should be protected from the elements, but the top should be removed in good weather as it is in constant danger of being broken during loading. Many operators leave the top off entirely and the driver must dress for the weather. A good demountable top will add to the comfort of the men and often helps to keep a good man at his job. TRAILERS