Human Factors Engineering
During World War II, behavioral scientists pooled their talents to help military systems engineers develop vehicle operating systems to be used by military trainees with little or no engineering or scientific training. Fitting machines and environments to man’s capabilities and limitations resulted in the emergence of new disciplines known as engineering psychology or human engineering. The relationship between highway design and operational techniques became a major concern of the BPR’s research program.
In the 1950’s a few engineering psychologists began to translate the findings of classical experimental psychology to tasks that confronted motorists operating their automobiles between towns and cities. They also attempted to determine the basic skills required of drivers. The early models of driver behavior are now recognized to be overly simplistic, but they alerted traffic engineers and other road authorities to the fact that most people using highways differ from highway designers and traffic engineers in their perception of the driving situation.
The 1950’s were characterized by three major approaches for incorporating driver characteristics into highway designs and traffic operations techniques. The first was an attempt to scale the difficulty of specific types of driving situations by measuring driver stress. The second was performance oriented research characterized by measurement of the driving patterns of large numbers of drivers on a variety of road environments and was an extension of studies undertaken by the Bureau of Public Roads in the 1930’s and 1940’s. The third was epidemiological research, aimed at establishing patterns of responses of drivers which would permit officials to improve their selection techniques or develop remedial training programs. Incorporation of driving behavior into highway design and operational techniques was a major concern of the BPR’s research program.
Behavior research in the 1960’s began to mature. A programmatic approach to determining driver capabilities and limitations was begun in the late 1950’s when a team of behavior scientists began to conduct sophisticated analyses of the perceptual environment faced by motorists traversing high-speed roadways on potential collision courses with other vehicles and obstacles. Fundamental work on road tracking, speed sensing, car following, overtaking and passing, object avoidance, sign reading, and path finding were performed jointly in BPR, several universities and by private contractors. Most notable among the collective agencies was the portion of a program of automated or semiautomatic vehicular control conducted by Ohio State University’s Industrial Engineering Department.
In the mid-1960’s, fundamental work aimed at delineating driving skills abated in favor of development of driving aids systems to assist motorists. Several such systems were identified to overcome high accident situations and basic limitations of motorists; developmental research study of them continues. Some of the traffic control and information systems were:
- A passing aid system to assist drivers in overtaking and passing on two- and three-lane highways.
- A merge control system to assist drivers in making complex decisions at freeway entrance ramps.
- An experimental route guidance system for assisting motorists in finding their way to unfamiliar destinations.
The knowledge developed through these programs and efforts of behavioral scientists have been inte-grated into modern highway design and traffic engineering.
Environmental Factors
Hydraulics and Hydrology
Hydraulics and hydrology, simply stated, are sciences developed to control the deleterious effects of water. There is adequate evidence that ancient cultures constructed amazingly elaborate conduits, aqueducts and other drainage structures to control the flow of water. In the early development of rail transportation, bridges and culverts were certainly an integral part of the design. With the advent of the automobile and accelerated highway construction programs, drainage and water problems became more critical. Bridge damage, washouts, and flooded roadways became intolerable, and paved surfaces required good drainage to reduce hazardous conditions for the movement of traffic and to prevent pavement failures. Progress in the control of water flow and drainage was slow, and in the early days, designs were based on judgment without uniform policy guidelines or well-developed engineering technology. It was common to size highway drainage structures by using a formula developed by Professor Talbot of the University of Illinois for the design of railroad structures being built in the western States in the 1890’s. That formula was the first attempt to provide a rational approach to drainage design; it was crude but an improvement over previous methods. However, it is interesting to note that in 1961, despite the fact that by then more sophisticated techniques had been developed, a survey by the American Society of Civil Engineers concerning drainage practice showed 12 States still using Talbot’s formula.
In the early 1920’s, David Yarnell pioneered in experimental hydraulic research with his study on the flow of water through culverts based on extensive full-scale tests conducted at the University of Iowa. Unfortunately the report covered only culverts flowing full. Most culverts do not flow full, and the factors affecting them are significantly different, Yarnell went on with experiments on flow resistance caused by pile trestles and flowover embankments. His work on rainfall intensity-frequency relations was published by the U.S. Department of Agriculture in the mid-1930’s and for many years was widely used across the country in determining the rainfall rate to apply in the use of the rational method of estimating runoff.
Highway engineers had also been concerned about erosion of highway ditches and slopes, but it took the demonstration projects of the Soil Conservation Service in the late 1930’s to show how flattening of slopes and rapid establishment of sod could control erosion. About the same time the Soil Conservation Service also began setting up experimental watershed stations in several locations to study rainfall-runoff relationships as affected by land use practices.
