ROAD CAPACITY

Evening Post, Volume CXV, Issue 11, 14 January 1933, Page 15

ROAD CAPACITY

THE ENGINEER'S PROBLEM

SOME THOUGHTS ON SPEED

The speed highway presents greater problems to the engineer than the average motorist is v apt to suppose. There is nothing in building a, car that will do anything from 50 to 60 or even 70 miles an hour and still be within the purchasing power of a ■ large proportion of the population, but there is a very great deal in/providing the kind of road on which such cars can be "operated with safety and satisfaction. It is not merely a ease of surfacing^ banking, and grading. These are costly matters that can be faced and over? com© provided there are sufficient revenue sources to be tapped. A greater trouble is that speed, which some imagine to provide the solution of traffic problems, does precisely the opposite; it limits and does not extend the capacity of a road to accommodate traffic. "Why is this? For the simple,reason, that the slower traffic proceeds the more cars can a single lane accommodate safely. With brakes in. good condition it takes 167 feet to stop.a car from fifty miles an hour. At such a speed no more than 31.6 cars to the mile should be trying to travel in one direction in one lane at any one time. At 20 miles an hour traffic is theoretically safe with 128.8 cars spaced in a lane a mile long, giving an hourly capacity of approximately 2600 vehicles, against approximately 1700 at 50 miles an hour. At 70 mile's an hour the drop would be to 1190 vehicles per hour. Actually, the engineers in America have decided that what is needed in the way of sight distance on a road that will permit a driver 60 miles an hour is no less than 1000 feet. It would be much more . for' a faster highway. Speed, therefore, imposes a severe restriction on the capacity of the rbad to accommodate traffic. Nature has not arranged the surface of the earth to make it easy to lay down motor surfaces. She has raised all sorts of obstacles, taking" the form of mountains, hills, chasms,' rivers, lakes, and the like. There are two ways of getting around such an obstruction. One is to remove it 'altogether. The other is to dodge it. Both cost money, but dodging costs less money than removal. The motoring public can have either, depending upon which it will pay for. Dodging is a process in which the road designer has acquired considerable skill. When the motor first came, or rather when the motor highway first began to be constructed, the towns and cities of both the Old World and the New had only one idea, and that was that whatever was done the main, highway must pass through them. For long that policy was maintained, and in many places—New Zealand not excluded— tho policy still; remains. The Idea was,of course, that the traffic would bring business. Up to a certain point it does; after that it brings only congestion. The present history of roading in England is far less a history of surfacing than a history of widening and of what is known as the by-pass. One of the greatest obstacles the road engineer now has to face is the man made obstacle of the town, with its dense traffic and congested streets. To the motorist it is worse than a mountain. Traffic is slowed to the point of, exasperation. The through vehicle refuses to stop; often it could not if it would, there being no place to park. The result was inevitable, a decline in property values on all main roads, and a problem for municipalities in the presence of traffic not belonging to them, of no assistance1 to them, and a hindrance to tho business and free, movement of all property pertaining to them. Two forces were thus -at work; the municipality must shoulder the burden and the through traffic itself, must avoid tho municipality. Hence the bypass. By-passing is essentially a spaed job; the main road is a speed job, and the engineer's task is to provide'a road to accommodate traffic at speed. The problem has not yet been solved. The nearest approacli is in America, with' its lane system, but the.lane system is not safe; neither is any other system ,so far promoted. v ■■'.:-' On the open road speed is essential, and the engineer must find a way. In the city the case is different. The day will come when municipalities will realiso that speed is not the clue to relief of congestion. The real relief will come from the removal of traffic that should not be there, the provision of arteries that give access, to tut avoid direct contact with shopping areas, that permit of parking without obstruction, that allow of a reasonable traffic flow so that jams are avoided and bursts of speed not required. No vehicle should enter a business" street unless it has business there or in the vicinity, and no vehicle should bo under the necessity of entering a business area to reach some place without it. The key to speedy city traffic is not speed, but routes and road capacity. There are many interests to consider—the people on foot by no means forgotten—but one thing is certain, the. city street 13 no place for speed, and speed is no. solution of city transport. It not only lessens street capacity, but it greatly, increases the danger to life and limi in the streets. For speed, speed streets are necessary, and until speed streets are built traffic should be kept' to the point of, greatest all-round efficiency.