Traffic control

It is obvious that in existing urban areas much of the congestion is due to narrow streets and junctions which are incapable of taking peak-hour traffic. The solutions of this problem are costly. They include adequate roundabouts and street widening and the segregation of traffic by means of flyover roads, underpasses, bridges and pedestrian subways.

Much of the congestion in urban areas is due to traffic which has no business in the area but is only passing through.

Signposting is, of course, a directional control and a very effective one. In fact it is important for all signs and symbols used on the roads to be seen well in advance by drivers approaching at normal speed. Directional control cannot increase the capacity of the highway system but it can avoid local congestion.

One-way traffic is a special kind of directional control which is very effective in maintaining the traffic flow in congested areas.

A major cause of congestion in towns is the interruption to the free flow of traffic by cross traffic at junctions. But if the need for traffic streams to cross each other can be avoided then the movement of vehicles will be much easier. This easier movement of traffic can often be achieved by making traffic move in one direction only along certain streets and by prohibiting incoming vehicles from side streets from crossing the main stream. The streets may be either one-way or two-way according to local conditions of traffic or width of carriageway, and traffic at the junctions can be guided by constructing suitably-shaped islands. Besides, one-way traffic can also be introduced where the carriageway width is inadequate for two opposing lines of traffic.

The two main objections to street intersections are that they are a cause of accidents and that they interrupt the flow of traffic. The best thing to do with intersections is to get rid of them. If that is not possible they may be improved and made safer but they will always remain a source of danger and delay.

Many accidents are caused because traffic streams of different types, or traffic streams travelling in different directions are using the same carriageway, and these accidents can be avoided either by reservations between traffic lanes, or by vertical (or “grade”) separation.

In many cities in America and in Europe segregation of traffic is achieved by means of flyovers or underpasses; at some junctions there are even three different levels. Each has its advantages and disadvantages according to the cir­cumstances. Flyover structures are not always aesthetically pleasing while an underpass may be more expensive to construct. The separation of fast and slow traffic from the heavier and faster traffic is most desirable not only in the interests of freedom of traffic movement, but also of safety. This ideal is not easy to achieve.

Urban traffic control will be of benefit to the general public in the district concerned and will result in greater comfort for road users of all classes, as well as bringing economic advantages to the community as a whole.

Source: Пособие по английскому языку для студентов II-III курсов строительных вузов / М.: Высш. школа, 1978. – C.27-29

Date: 2015-12-12; view: 735; Нарушение авторских прав