The average truck combination ravels over 49,000 miles per year, and this increases to more than 77,700 miles annually for the average major for-hire motor carriers. In fact, some individual truck tractors exceed 150,000 miles per year. Smaller, local, trucks typically travel about 25,000 miles each year - mostly within urban and suburban environments. The purpose of this research was to determine how many persons actually see these trucks in traffic in the course of a year, a mile, or an hour. Also to be determined was the portion of a truck actually viewed the front, the sides, and/or the rear - plus the length of time that other vehicles typically follow a truck under varying traffic conditions. As a "spin-off" of the research performed, average road speeds were determined for ten highway classes. Finally, a separate analysis was made of the sizes and shapes of signs most appropriate to traffic conditions - in terms of legibility and visibility distance. To add validity to the data base which this project creates, field research was carried out in four areas of the country; utilizing only highways and streets known to be major truck routes. The Philadelphia/Camden area is considered to be typical of the Eastern traffic patterns and Pennsylvania has the third highest truck registration in the Nation. Houston is typical of the open Southern/Southwestern environment, with Texas being the situs of the second largest number of registered trucks in the U.S. Chicago is recognized as the largest single transportation center in the country, while California has the largest number of trucks licensed n any state. In California, field surveys were made throughout the bay area; embracing San Francisco, San Jose and Oakland. To further refine the data base, analyses were conducted on ten different types of rural, suburban and urban roads and streets. With the exception of four special night comparison tests, all surveys were made during mid-week non-rush-hours of non-holiday weeks in July and August 1977. Federal traffic manuals indicate that measurements of traffic taken at such periods are considered to be typical of average annual daily conditions. It is estimated that the final results obtained for visual impacts represent an approximate five percent understatement of a true universe, and may thus be considered conservative. Separate measurements were made of the length of time that a vehicle will follow a truck under differing traffic conditions and on various types of roads and streets. Sufficient data were assembled to allow for analysis of causal relationships and to permit the drawing of certain general conclusions. In the course of the test operations, average operating speeds were obtained for all road sections analyzed. These were separately tabulated and averaged by type and classification of highway - and the data were compared with published Federal vehicle speed information. The comparisons confirmed the validity of the test data when variations in traffic conditions were taken into account. The final section of the project report consists of a literature search and commentary on the subject of sign sizes and designs. Working from the premise that established standards for highway and airport taxiway/guideway signs reflect research already accomplished relative to the problems of legibility of messages directed toward occupants of vehicles in motion, these standards were examined, listed and compared. in the report appendix, a full explanation is presented of the methodologies employed in carrying out the visual impact survey. Copies of instructional material and worksheets are included as well as a log of all highways examined. (Author/publisher) To receive a copy of this report please visit: http://www.atri-online.org/
Samenvatting