The French unit of traffic is technically known as the “collar,” a draft animal harnessed to a wagon being counted as 1.0. The metric ton, 1000 kg., is also sometimes used. The French, feeling that the dead weight of a vehicle or animal did not truly measure its effect as to wear on a road surface, classified the traffic and assigned importance factors to the several classes. From 1882 to 1903 the classification consisted of: 1st, Trucks and farm wagons, loaded; 2d, Public vehicles designed for transporting passengers and their baggage; 3d, Light vehicles, such as private vehicles, and empty farm wagons; 4th, Larger animals, such as horses, mounted or not, mules, and large cattle; 5th, Small beasts, such as sheep, goats, and pigs. In 1903 motor vehicles were separately listed; they were divided into five classes: 1st, Metallic-tired automobiles, “which in general are heavily loaded, have a slow movement and produce the effect of wearing away the road surface”; 2d, Elastic tired automobiles licensed to make a speed of not more than 30 km. per hour; 3d, Automobiles whose speed was less than 30 km. per hour; 4th, Bicycles or velocipedes propelled by the feet of the rider; and 5th, Motor cycles, whether having two, three, or four wheels. The report of the second international road congress further states that “it is necessary to attribute to each element of the traffic an importance which belongs to it from the viewpoint of the destructive effect exercised on the road crust.” Consequently the numbers of vehicles or animals in the several classes were modified by multiplying them by importance factors arbitrarily assumed. Importance Classification factors An animal harnessed to a loaded vehicle 1 collar Loaded trucks and farm wagons 1 Public vehicles for transporting passengers 1 Light vehicles, and empty farm wagons ¹⁄₂ Harnessed horses to light vehicle or empty wagon ¹⁄₄ Mounted horses or with load on back ¹⁄₄ Unharnessed horses ¹⁄₅ Cattle ¹⁄₅ Small beasts (sheep, pigs, goats) ¹⁄₃₀ Automobiles with metallic tires, weight in metric tons times 1¹⁄₄ = No. of collars Automobiles with elastic tires Motor cycles ³⁄₁₀ Vehicles licensed to make a speed over 30 km. per hour 3 Vehicles licensed to make a speed of less than 30 km. per hour 1 From this it was possible to reduce all traffic to the unit “collar,” which was used as a comparative measure of the use of the several roadways. The tonnage was calculated by multiplying the numbers by average weights obtained by weighing a sufficiently large number of the units in each class.