Traffic flow

“ Among the more lightly traveled of existing highways approximating the location of sections of the system, substantial conformity to the less exacting standards Proposed for such sections of the system is more common. But of these more lightly traveled highways, even, a large mileage cannot be regarded as an acceptable addition to the system without major improvement—improvement which again involves the provision of features of free traffic flow to a greater extent than the provision of adequate road surfaces. ”

“ The large volumes of traffic that now flow between densely populated localities have created a demand for wide, multiple-lane highways, built according to the highest standards of grade and alinement, with opposing traffic separated by a center parkway, bypassing all cities, with structures separating streams of traffic at all highway and rail crossings, and with access from side roads permitted only at carefully selected points. ”

“ The present flow of traffic within the city is affected by the existing pattern of land use, the existing location of railroad and other transportation terminals, the existing concentrations of business, industrial, and cultural establishments, and the existing location of residential areas of various classes. It is probable that many of these existing land uses will be materially changed within the life period of any substantial new traffic facilities now provided. ”

“ But at just about the time when this process is fully completed, the volume of traffic flowing over the street is apt to have become so great that everybody recognizes the street to be too narrow for the increased traffic it has now to carry. ”

“ At certain types of junctions where there is two-phase control, such as T junctions, staggered crossroads and junctions with one-way streets, we think that additional signals should more frequently be installed to ensure that pedestrians can see not only the signals controlling the traffic stream they are about to cross but also those for traffic flowing at right angles. ”

“ People traverse it, not with the object of arriving at any particular destination, but for the delight of the road itself, of the joy it gives to the eye and to the imagination. Its only traffic is what the transport agent would call “holiday traffic”; for when the idle season ends the highway is deserted. In earlier days there would rumble along the road the carriage and four of the traveller of great means; then came the humbler vehicle hired from the town; then the sleek motor; and finally, as a sign of democratic progress, the char-à-banc, the omnibus, and the motor-brake. ”

“ The climatic conditions are readily obtained from the Weather Bureau, and a satisfactory record of the volume and character of the traffic can be made by any competent person living in view of the road.
In France the measuring of traffic has received a great deal of attention, and a census is kept for all the national highways. The traffic there is rated and reduced to units in the following manner: A horse hauling a public vehicle or cart loaded with produce or merchandise is considered as the unit of traffic. Each horse hauling an empty cart or private carriage counts as one-half unit ”

“ And with all the finesse of their work the traffic moves like molasses. Long double and triple files of touring cars and limousines, the combined cost of which would render statistics such as would gladden the heart of a Sunday editor, make their way up and down the great street tediously. If a man is in a hurry he has no business even to essay the Avenue. And occasionally the whole tangle is double-tangled. The shriek of a fire-engine up a side street or the clang of an ambulance demanding a clear right-of-way makes the traffic question no easier. ”

“ In industrial districts there is a large volume of this class of traffic consisting of motor passenger vehicles used for business and for pleasure and of motor freight vehicles used for general business purposes. In addition, there is certain to be a large amount of motor truck freight traffic incident to the particular industrial pursuits of the cities. Where adequate public highways connect industrial centers, there is invariably a very large amount of inter-city traffic, due in part to the needs of industry and in part to concentration of population in industrial centers. ”

“ On a street carrying a daily traffic of 10,000 vehicles, if this traffic were equally distributed throughout the 24-hour day, one such traffic light operated on a half-minute interval would prevent 739 vehicle-miles of movement in a single day. ”

“ In consequence there is often on such relatively short sections of highway an actual development of congestion or an approach to it.
If we inquire into the reason for the failure to augment the traffic facility in proportion to the increase in traffic we usually encounter right-of-way difficulties. At the approach to the city road-bordering developments thicken to such an extent that the additional space required for the widening or other increase of the highway facility may be obtainable only at heavy cost because of the closely crowding suburban residences and industrial establishments. ”

“ To simplify the matter somewhat, the different classes of traffic to which roads are subjected may be divided into five groups, which may be called city, urban, suburban, highway, and country road traffic, respectively. City traffic is a traffic so great that no macadam road can withstand it, and is such as exists on the business streets of large cities. ”

“ Where such a smaller city lies between larger ones closely spaced, the usually heavy traffic moving between the larger cities is likely to be a preponderant part of the volume on the main highway at the limits of the smaller intermediate city, and the diversion of this traffic over a bypass around the smaller city may considerably reduce the traffic volume on the connecting streets in the city. ”

“ At the intersection of important highways, the problem is complicated by the necessity for providing for through traffic in both directions and for traffic which may turn in either direction and the engineer must provide safe roadways for each class of traffic.
Tractive Resistance.—The adoption of a policy regarding the grades on a road involves an understanding of the effect of variation in the character of the surface and in rate of grade upon the energy required to transport a load [Pg 50] over the highway. ”

“ But instances are rare indeed in which the congestion of through highways in cities has been attacked at its principal root—the frequent grade intersection of cross streets. Instead of eliminating this principal cause of traffic delay, city authorities have generally resorted to the installation of traffic lights for control of the intersecting traffic streams and the prevention of accidents, and this expedient measure has in some cases been so applied as to increase rather than reduce the obstruction of traffic. ”

“ To incorporate within each of the several mileage limits adopted, those principal highway routes which would reach to all sections of the country, form within themselves a complete network, and jointly attract and adequately serve a greater traffic volume than any other system of equal extent and condition. ”

“ There is ample support for a legislative determination that the peculiar character of this traffic involves a special type of use of the highways, with enhanced wear and tear on the roads and augmented hazards to other traffic, which imposes on the state a heavier financial burden for highway maintenance and policing than do other types of motor car traffic. ”

“ Where traffic on the rural routes is heavy and, in the environs of cities, where it is desirable to discourage undue extension of road-bordering city growth, prohibition of access to the highway from abutting land, controlled access at specified points, and the closure or grade separation of all intersecting highways are essential. ”

“ In planning improvements of highway systems, it is recognized that one or more of several groups of traffic may be encountered and that the extent and nature of the improvement must be such as will meet the requirements of all classes of traffic, the most important being first provided for, and that of lesser importance as rapidly as finances permit. ”

“ In their urban and suburban sections, the interregional routes will carry a heavy, bustling traffic. Adequately landscaped borders will eliminate the traffic hazards of closely crowding buildings, and insulate adjacent residential and business properties, churches, and schools from the noise, dust, and fumes of traffic. ”

“ In establishing one-way streets attempts are usually made to avoid left-hand turns whenever possible. The figures on pp. 424 and 426 show sketch plans for rotary service. When there are street-car tracks or other local obstructions slight changes may have to be made. Note only two full passing places for vehicles, A, and as only a part of the traffic will want to cross congestion and danger are largely eliminated. There may be one, two, or more lines of traffic at B; depending on the width of the street. ”

“ We believe that an effective step which could be taken to reduce these casualties would be to ensure that at the great majority of junctions, and certainly at those junctions where serious danger exists, the minor road is distinguished from the major so that drivers on the minor road are given a clear indication that they should give way to major road traffic. ”

“ Investigations of the fluctuations in traffic movement show that a highway planned to accommodate the traffic demand during the peak hour of the average day of a year will be congested, on an average, during 160 days of the year. ”

“ These additional data show clearly that, for truck traffic at least, the percentage of the main-highway movement originating in or destined to cities, rises with the increasing range of movement. For the seven States and regions represented in the table, cities are involved as the origin or destination or both in 87.0 percent of the intrastate or short-range movement, 95.5 percent of the interstate or longer range movement, and 96.7 percent of the transstate traffic, or traffic of longest range. ”

“ As important as the interconnection of cities is, however, ideal directness of connection between the largest centers was not attempted, All highway traffic is a composition of long-range and short-range movement, and the highway planning surveys have shown that the latter is the predominant element on all roads. Normally, for example, about 85 percent of all trips are for less than 20 miles, and only about 5 percent for more than 50 miles. ”

“ The character of the interregional routes as main collectors of through traffic justifies the granting of preferential right-of-way to traffic moving on them over all crossing and entering traffic everywhere, throughout the system. A proper facilitation of the express traffic with due regard for safety and economy requires, moreover, a reduction of the number of access and crossing points to a practicable minimum. ”

“ Proper regulation and control of traffic are accordingly as essential to a GOOD highway system as are proper plans for its building and the use of proper materials in its construction.
Engineers and builders are the men behind the line in the battle for good roads. Maintenance forces and traffic officers are the men on the firing line. The maintenance engineers must see that roads once built are maintained in adequate condition for travel. Traffic officers must see that travel uses these roads properly. ”

“ It may also be desirable to illuminate throughout their length rural sections of the system expected to carry large volumes of traffic, particularly if the traffic includes a large percentage of commercial vehicles. ”

“ When one observes the countless impediments that embarrass the movement of twentieth-century traffic through the eighteenth century streets of some eastern cities one wonders how long it will be, with the assured further increase in traffic, before complete congestion will result. ”

“ From all the testimony we think there is ample ground for believing that the improved road will lead to an increase in the traffic and revenue of the railroad, as respects freight moving in carload lots and passengers traveling considerable distances, but that the benefit from this will be cut down by a substantial loss in local freight and passenger traffic attracted to motordriven vehicles moving over the improved road. ”

“ When the traffic volume on a two-lane road does not exceed 300 vehicles per hour the congestion on grades resulting from slow-moving vehicles in numbers normally found on main highways is not sufficient to justify the construction of a third lane, regardless of the alinement and profile, for grades up to 7 percent. ”

“ On rural two-lane sections of the system expected to carry an average daily traffic volume of 2,000 vehicles or more, where it is not feasible to provide the minimum passing sight distance recommended in table 3, two lanes shall be provided for traffic in each direction. ”

“ In the method of control known as the flexible progressive system the signals at a number of adjacent junctions can be co-ordinated in such a way that traffic may proceed at a uniform speed along the main thoroughfare without being held up at each successive intersection, while at the same time frequent opportunities are given for cross traffic to proceed. ”

“ The big percent is one way traffic. To get a block or so away from where you are you execute some geometric figures they didn't have in the books when I took geometry.
This day we had an accident. Driving in the downtown congestion a car from the lane to our right pulled into us, tearing off the right hind fender of our almost brand new convertible. Traffic stopped momentarily only. You would think the two owners were exchanging pleasantries. They gathered up the pieces and pulled out what was left of the fender to keep the tires from scraping, and away we went. ”