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COLLISIONS IN STREET AND HIGHWAY TRANSPORTATION
W. J. Sidis
21. Social Aspects of the Transportation Problem. It should also be noted that the benefits derived from the use of motor vehicles may be considered from the standpoint of intangibles. This point is especially useful in considering mass transportation by street cars, etc. The street cars in many cities have lost patronage to private automobiles, buses, and taxicabs, because the street cars had, in addition to certain disadvantages of a physical nature, such as slow speed, waiting time, walking required to and from cars, etc., disadvantages affecting the mental attitude of the patron. The intangible, as well as the physical factors, account for the adoption of the private automobile in large numbers for family and individual use. One of the most important of these intangible factors, is the crowding of very different social classes into a small inclosure, a street car for instance. The question of service afforded by street cars and other common carriers used in mass transportation, is of the greatest importance when considered in connection with street safety. The presence of large numbers of private automobiles, taxicabs, and pedestrians upon city streets and intercity highways is due, in no small measure, to lack of adequate and inviting mass transportation systems.
22. The Engineer's Problem of Street and Highway Safety.
23. Space Limitations and Existing Structures. In attacking the safety problem upon city streets, we are met by certain conditions which sharply limit the freedom of action of the designer. Aside from the psychological characteristics of the humans who constitute the pedestrians, and passengers and drivers of vehicles, there are legal questions, especially those pertaining to building lines which limit the geographical area at the disposal of the designer. General methods of constructing such highway features as sidewalks, street car tracks, drainage, etc., have been standardized for so many years, and the opinions of the public and highway engineers upon such questions so thoroughly fixed that it is difficult to get an appreciable amount of consideration for new ideas. Street improvements, like the buildings that face upon them, are solidified in expensive masses of brick, concrete, etc., and a proposal to make radical changes may sound appalling or ridiculous.
24. Radical Trend of Thought. On the other hand, a considerable amount of effort has been spent by engineers and students in proposals which, if carried out, would involve radical changes, not only of street arrangements, but of building construction. The most important idea along this line is the multi-level arrangement of streets and side-walks. This idea will be discussed more in detail under "The supercity" (253).
25. Proposals for Solution. Between the reactionary element, that is the public and its employed engineers, and the radical element, that is the city planning students, the way out seems to be along experimental lines. Wholesale changes in structures, based upon untried suggestions, will undoubtedly not be made. On the other hand, experiments upon street layouts are not usually within the range of effort of even a good experimental engineer. It seems apparent that experiments with street arrangements are urgently needed in order to break a deadlock which now exists. Traffic experiments are by no means unknown to the public. The very act of driving a vehicle, especially through unfamiliar territory, is in a sense, an experiment, and one that occasionally turns out disastrously. The rules of driving cars are, to a considerable extent, the results of experiments; and changes and experiments in rules and even laws are always in progress. Traffic signal installations, especially, have been subject to experimental attempts.
26. The Kinematical Problem of the Vehicle. The study of a vehicle or of a number of vehicles moving over the streets, should be handled as a kinematical problem and analyzed by those qualified to make such a study, but judging by the literature on the subject, no such kinematical study has ever been made. Contributions have been made by certain writers who have had practical driving experience, and by engineers interested in the manufacture and operation of traffic control devices, all quite incomplete. The possible motions of a motor vehicle, controlled largely by the whim of the driver, seem to place it outside of the realm of scientific analysis. In actual practice, drivers are always on the alert to seize upon any trifling advantage in a traffic situation, even though rules are broken, public safety endangered, and traffic delayed. The tendency towards mutual interference among motor vehicles, is one of the worst phases of the traffic problem.
27. The Statistical Method of Study. The statistical method of studying motor-vehicle accidents is frequently employed, and generalized deductions have been useful in designing certain features of street and highway construction, and designing motor vehicles, and developing control and regulation methods. It would seem, however, that this method has not been developed intensively enough. Statistical information should be collected by municipalities and States and published. This information should show details of conditions existing at times and places of collisions. For instance: information that certain days or hours of the week are most productive of accidents, is interesting but leads to no important remedy; but statistics showing that there are fewer accidents at controlled intersections, are of prime importance. This subject might be discussed at considerable length, but since this discussion appears to be mostly speculative, it is dismissed rather briefly here.
28. The Correlation Between Collisions and
The prevailing idea among statistical students is to find a correlation between
the numbers of persons killed and injured by motor-vehicle collisions, and
another variable such as registrations of motor vehicles. In the past, a
reduction in the ratio of fatalities to registrations was regarded favorably,
and was presumed to indicate a measure of success in the control of the problem.
This ratio did, in fact, decrease rather steadily year by year. The disturbing
point of actually large numbers of fatalities and injuries, and high yearly
rates of increase in the same figures, has not been satisfactorily explained
from a statistical or any other standpoint. Frequently, the suggestion is made
that there is a correlation between a continuous increase in the accident rate,
and a similar increase in the mean average speed of motor vehicles. The author
inclines to this view; but to secure reasonably reliable statistical information
concerning the mean average speed of motor vehicles for any period, past or
present, would be a matter of extraordinary difficulty. Also, there are many
other factors important enough to affect safety, but difficult to correlate to
the extent of plotting a curve; street width, for instance.
29. City Planning. Many students approach the traffic problem as a sub-topic under the more general subject of city planning. Unfortunately, the safety question is likely to be submerged in the vast field for discussion which modern ideas on city planning open up. Nearly all American cities have been built without adequate initial plan. Rebuilding the city is entirely out of the question, and city planning is principally useful in development work.
30. Relation of City Planning to Traffic
important subtopics under city planning must necessarily be considered in
connection with a complete study of traffic safety. They are:
31. Decentralization of the People from Densely Populated Areas. The uncomfortable and degrading conditions attendant upon living in crowded situations, has brought to city planners the problem of attempting to find methods of dispersal of the population from densely populated sections of cities. The whole problem is quite complicated and many factors are beyond direct and immediate control. Present-day intensive studies of building and housing are undoubtedly effective in securing the desired relocation of some sections of the population of certain districts. The automobile is probably the most important agent at work in effecting decentralization. The street car systems as formerly developed, were instrumental in causing centralization, especially of industrial and commercial populations; but with buses as adjuncts and an up-to-date viewpoint, the street car may compete favorably with the private automobile as a decentralizer. The relationship of the problem of decentralization to that of traffic safety is not readily apparent. Presumably a decentralized population will have increased need for transportation and the demand for traffic safety will be correspondingly augmented.
32. Zoning and Public Reservations. The subjects: zoning, building height, public reservations, children's playgrounds, and other related questions are important, but of such a nature that we will probably be obliged to wait upon a slow, though steady development for results in these fields, in so far as they affect the safety problem. It is hardly to be expected that the efforts of any one person, or even of a group, will be sufficiently powerful to exercise a marked control over this development. The traffic engineer will be obliged to construct for, and control traffic within the confines set by existing building lines.
33. Proposed Community Areas. The proposal to lay out "community areas" is attracting considerable attention among city planners. The primary traffic idea involved in the community area is that of making the streets within the area impossible of use by through traffic not destined for a point within the area. Well designed "through" or "express" streets will serve as the boundaries for the community areas. It is expected that the community population, especially the children, will have only infrequent need to cross the express streets. The express streets will carry a considerable volume of high speed traffic.
34. Adapted to New Subdivisions. The community area idea does not appear adapted to the problems of built up districts, but it is particularly applicable to unimproved areas adjacent to cities and towns, or as the initial plan for a new municipality. It is expected that the community area will afford vastly improved living conditions over the typical case of residences abutting directly upon city streets.
35. Local Streets. No attempt will be made here to describe the manifold advantages of the community area as to its effects upon the commercial, educational, and social welfare of the inhabitants. Our interest is in the safety question as it applies to the maze-like pattern of local streets within the area, and to the express streets between adjacent community areas. To merely lay out a maze of streets with turnings, cul-de-sacs, curved streets, and circles or similar plots at the intersections, without making a safety study of the plat along advanced lines, will be to invite an accident rate comparable to the present rate as found in residential districts. In the absence of sufficient actual experience with the maze pattern as an intended design, it seems entirely problematical as to whether speeds of vehicles on these local streets can be held low enough to secure increased safety, and whether pedestrians and vehicles will be less likely to collide. The all-important question is whether the intersections within the community areas will require traffic signals.
36. Express Streets. The express streets will carry an amount of traffic proportionately larger than present-day "arterial highways," therefore they are likely to be wider than many of our present much-travelled streets. To design these wide streets for a large volume of high speed traffic, will require safety studies of the very highest order. "Arterial highways" are recognized as being the scenes of a large proportion of our automobile fatalities. Endeavor will of course be made to separate the grades at express intersections. The problem of channelization of traffic will probably supply the major difficulty for the designer of these streets, and for those charged with the safety of the pedestrians and vehicles using them. In subsequent paragraphs under appropriate headings, the author has made suggestions which it is believed will improve safety conditions upon our city streets. These suggestions are directly applicable to the local and express streets of community areas.
37. Motor-Vehicle Service Stations. Incidentally, in connection with our consideration of zoning, there is one problem which affects the traffic safety question directly, and that relates to service stations selling gasoline, tires, and other supplies and service to vehicle drivers. Whether these stations are so situated as to require the vehicle to stand at the curb, or to be driven across the sidewalk into private ground, they represent a growing problem by reason of the obstruction created by vehicles serviced at the curb, or the dangers created by vehicles frequently passing over the sidewalk. The application of the zoning laws to this class of structure, should involve consideration, not only of the suitability of a service station to a certain building location, but of the question of public safety and convenience upon the sidewalk and highway. The author's proposal under the heading "Under City Sidewalks" (57), will solve this problem satisfactorily by permitting vehicles to enter private property from the street without crossing the sidewalk.
38. Mass Transportation, Including Street Layout, City Freight Transportation, and Vehicle Parking. A considerably more detailed discussion of this fundamentally important subject is reserved for the latter part of this book, but some salient points may well be alluded to here. The question of street layout seems to bear most heavily upon the difficulties encountered by the present-day traffic engineer who endeavors, in a given location, to bring a semblance of order into a chaotic traffic condition.
39. The "Balanced Grid." The engineer should strive to achieve the complete "balanced grid" of streets dividing the area into equal-sided rectangles or "squares." A balanced grid may be defined as a street plan permitting traffic to equalize or flow readily in all directions. Any obstacle affecting the "through" nature of a street, should be eliminated wherever possible. An exception to the last statement is found at multiple or in some cases, offset or sharp-angled intersections where a central plot, usually referred to as a "circle," may be introduced to cause rotary movement of traffic. Efforts of early, as well as modern, city planners to secure unique effects upon the landscape by introducing crooked streets, offsets, blocked streets, and irregular layouts of one kind or another are, to all intents and purposes, effective in producing congestion upon other streets, and an unbalanced flow of traffic.
40. "Arteries." The frequency with which the term "artery" is used, might lead one to believe that streets of this type were desirable. The author would like to express his objection to the term, and also to traffic-control methods which tend to create excess traffic upon some streets by the inefficient use of adjoining or parallel streets.
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