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Show Speed limit through county's i nterstate should be 65 mph By GARY R. BLODGETT BOUNTIFUL - Discrepancies in the method of determining the speed limit on an interstate highway were outlined today by a former safety studies engineer for the Utah Department of Transportation. Blair G. Marsden, who served as UDOT's safety studies engineer until un-til a year ago, said, he became so disgruntled with the federal rules and regulations that had to be followed that he left his position for a consulting job in Phoenix, Ariz. "It's just not realistic to base the speed limit on a rural interstate highway by the population of a metropolitan area -- especially when the metropolitan area is a combination of two or more cities," he said. For example, he noted, there is no traffic safety reason for 1-15 through Davis County to be anything but 65 miles per hour, "The highway is designed for at least 65 mph, and there are no major interchanges which would warrant a reduced speed," he said. "But there were never any traffic safety and highway condition studies made to determine the speed limit; everything was based on population in the area." Referring to traffic and highway studies that he feels are necessary to gain a "true picture" of a recommended recom-mended speed limit, it is essential that speed tests be conducted at various sites on the highway to determine de-termine driving habits of the majority of the motorists. Then the basis for determining a safe speed limit should fall within the 85 percentile of the motorists. For example, study at random --under --under fau weather conditions and with nq highway obstructions - the speed of 200 vehicles. Then throw out the speeds of the 30 fastest vehicles, assuming that the remaining 85 percentile will be "reasonable and proper speeds for the highway conditions." The average speed of those remaining re-maining 85 percent of the vehicles tested can then be determined. On Highway 15 in south Davis County, when the 55 mph limit was in effect, the average speed of the 85 percentile was 61,7 mph. When the speed limit was raised in one-area one-area to 65 mph, the average speed increased by only one-half mile per hour, to 62.3 mph. "This told me in those studies that the motorists changed their speed very little when moving from one speed zone to another - and the speed, limit should be a consistent 65 mph throughout all Davis County," Coun-ty," ' said. Mr. Marsden. He also emphasized ' that the "pace" speed of motorists should be considered when speed limits are established or changed. Motorists today travel a variance of up to 10 miles per hour when in a 55 mph zone. But in a 65 mph zone, that speed variance will be less than four miles per hour. Also, he noted, interstate highway accidents in Utah increased increas-ed very slightly with the increased speed of 65 mph, but the seriousness seri-ousness of the accidents, of course, increased with the higher speed. Mr. Marsden said there are several answers to eliminating the "hodge-podge" of speed zones in Utah. "The most simple," he said, "would be to have the federal government allow each state to perform per-form its own highway safety studies and determine their own speed limits based on the 85 percentile plan. Then let the states control their own speed laws. " He explained that the Federal Highway Administration established estab-lished the criteria for interstate highway speed limits based on populations and highway conditions in the eastern United States. "They had little knowledge or concern for the West," said Mr. Marsden. "We found that out when the chairman of the Highway Safety Committee for the Joint House and Senate came to Utah for a visit" Mr. Marsden said they drove from Salt Lake City to Wendover at the posted 55 mph. Less than two weeks later, Code 23, U.S. Annotated, An-notated, 1986, was passed by Congress, Con-gress, which allows 65 mph speed limits in rural areas. The bottom line, Mr. Marsden explained, is that motorists gear their driving speed to the environment, and they do not always see a posted speed sign. "To change from one speed zone to another, under similar highway) conditions, is not right," he said. "Never should there be a speed zone change on an interstate highway in less than 10 miles distance." He said he could understand the reasoning for funding states by the criteria used with the population as a basis, but this criteria should not have been carried over for determining deter-mining the speed limits of Interstate highways. Presently, if Utah, or parts of the state, don't comply with the FHA guidelines for establishing and enforcing en-forcing interstate highway speed zones, the state could lose as much as $40 million in federal highway grants, Mr. Marsden emphasized. |
