Modern Road Practice

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great many 2-lane highways have been built 20 feet wide but already there is a trend toward greater width. Many new surfaces are being built to a width of 2 2 feet, and a surfaced width of 24 feet will soon come to be recognized as a desirable standard for important 2-lane roads. Provision of a third lane is some times resorted to where two lanes are not sufficient but because of the danger in using the middle lane it is not a satisfactory solution of traffic congestion problems. Where two lanes are not sufficient, four lanes should be provided. For great volumes of traffic such as flow on main highways adjacent to large cities, the multiple lane highway is the only satisfactory solution. Ex perience with the first 4-lane highways has shown that traffic flowing in opposite directions must be separated by a dividing strip of some sort if a heavy accident toll is to be avoided.

The greatest congestion, the worst traffic snarls, and a large portion of the highway accidents are found on the main highways in and near cities. Only the provision of major improvements at a large cost will provide a solution. There is need for express highways cut directly into and through the centre of big cities. These are needed for the service of through traffic and for the daily in-and-out movement of local traffic between the downtown section and the suburbs. By preference such express highways should be constructed as depressed thoroughfares passing under all cross streets.

Elimination of crossings of railroads at grade is one of the most important features of the current highway program. Since 1933, nearly 3,00o crossings have been eliminated in the Federal highway program. This is a large contribution to highway safety and saves much delay and inconvenience to public travel.

About 75% of the rural population is located on secondary or local roads. Improvement of a selected system of these roads is needed to give better access to rural property and to improve social conditions.

The United States Highway System.

Through the co operation of all States and the Federal Government, effected initially through the agency of the Joint Board on Interstate High ways, and continued by the American Association of State High way Officials, a system of main transcontinental highways, known as the U.S. highway system, was designated in 1926. This system, which is a portion of the Federal-aid system, includes approxi mately 127,000 miles, composing 26 through routes, many of which extend from one border of the country to the other. The various routes are designated by the distinctive numbers which are displayed upon them, on standard, shield-shaped markers. The standard signs adopted are of two general classes. One group, the danger and caution signs, are of four different shapes represent ing as many degrees of danger. These have a yellow background with black letters and symbols. The other group includes the standard route marker in the form of a U.S. shield and directional and informational signs, with white backgrounds and black letters.

Highway Planning Surveys.

The Public Roads Adminis tration is co-operating with the highway departments of 46 States in conducting State-wide highway planning surveys. Most of the States are now at the end of the pioneer period of road develop ment and the surveys are intended to supply the information needed in planning the broader programs necessary in the future.

The surveys are the most comprehensive of any yet undertaken. Th'ey are being conducted according to a general plan developed by the Public Roads Administration, since it is particularly im portant that data collected in the various States be on a com parable basis.

A representative of the Administration is assigned to each State to keep contact between the Washington organization and the State survey organization. Each State organization consists of a manager, an assistant manager for each of the three main branches of the survey, and an office force and field parties, as required. The three branches of the survey are a road inventory, a traffic survey, and a financial and road-use survey. In the road inventory complete records of all existing roads will be obtained, together with a determination of their condition and the property they serve. Both State and county maps will be prepared by the States, giving for the first time a complete picture of our road system. The traffic surveys will result in information as to the character and volume of traffic on each section of highway from which the present relative importance of each highway may be determined. In the financial and road-use surveys studies are being made of the sources from which highway revenues come, the purposes for which they are expended, and the extent to which rural and urban residents contribute to each class of road and the amount they travel each class of road. Each State survey is to cover a period of one year. It is believed that the surveys will result in the assembly of all the facts necessary for the formu lation of a definite, economically and socially defensible, intei grated highway improvement program.

Highway Research.

As a result of the co-operation of the Public Roads Administration with State highway departments and universities, in scientific research looking to the development of types of construction and methods of administration and finance adequate to meet the demands of the fast-growing traffic, there is being built up a new science of highway engineering.

The investigations conducted include studies of the character istics of materials; determination of the forces applied to road surfaces by standing and moving vehicles; of stresses developed in the structure of roads and bridges by live loads, and by tem perature and other natural causes; analyses of subgrade soils and tests of methods designed for their improvement; studies of the flow of water through drainage structures, of the run-off from drainage areas, of the effect of moisture on soils and many others of fundamental importance and value.

The tests made on the Bates road in Illinois, the Pittsburg (Calif.) experiments, the impact tests at Arlington, Va., and the intensive studies of highway traffic conducted by the Public Roads Administration in co-operation with the authorities of many of the different States, were made in the interest of scientific research, and they have yielded data of considerable value to the highway engineer.