Test 1.Functional classification of highways.

The importance of motor roads for the national economy is closely related to the intensity of traffic on them, i.e., the higher the traffic intensity, the better should be the standard of design. Where traffic intensity is high the expenditure necessary for the construction of the road to follow the most direct route and with shallow gradients will soon be compensated by the economy in traffic operation. On the other hand, if in spite of a high traffic intensity the road is built with steep gradients and a narrow carriageway , though its capital cost may be much lower it will not permit the most effective performance of vehicles to be realized , in particular the maintenance of high vehicle speeds. In the long run, the cost of motor transport operation would become excessive.

The question of choice of the type of road, however, does not depend exclusively on the cost of construction. A number of other factors must be taken into consideration, particularly the part to be played by the specific highway in the transport system of the national economy.

There is a number of roads which are built according to high technical standards in spite of their comparatively low traffic intensity.

When designing roads to be constructed in new, sparsely populated regions, the expected traffic intensity cannot be the only criterion. In spite of the expected low traffic intensity for a number of years to come, such roads will constitute the main artery for populating these regions, Therefore, such roads can be built with a view to district, development, according to technical standards corresponding to a traffic intensity exceeding the present rate.

The motor roads are divided into five technical classes. The class is determined according to the importance of the road for the national economy. At the same time potential traffic intensities are considered, as well as the construction difficulties arising from the topographic features of the country in which the road is to be located.

The elements of the plan, profile and cross-section are designed with a view to the traffic intensities to be expected in 20 years, and the road pavement - in 5 to 10 years, depending on its construction and the possibility to strengthen it gradually.

Class I comprises roads having special economic, administrative or cultural importance for the national economy and having a high initial or potential traffic intensity; class II comprises similar roads with an appreciable potential traffic intensity; class III covers motor roads with a moderate traffic intensify but having a very .great importance for the national economy of the republics class IV includes roads having .local economic, administrative or cultural importance and a low traffic intensity; and с1ass V covers motor roads with small initial and potential traffic intensity.

All road elements of each technical class are designed to ensure the safe running of vehicles under normal conditions of cohesion between vehicle wheels and the carriageway surface.