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SPEED LIMIT <br /> <br />CHANGES CHAPTER 13 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />! <br />I <br />I <br />I <br /> i <br /> I <br /> <br /> Speed limits should be determined by an En- <br /> giheering and Traffic Study of the street sec- <br /> tion involved. Of consideration in reviewing <br /> a speed limit change should be the 85th per- <br /> centile speed ( at which 85% of the traffic is <br /> traveling slower than this speed), the location <br /> of sidewalks, driveways, obstructions, the <br /> horizontal and vertical alignment of the <br /> street, the use of the street by pedestrians and <br /> the existence of hazards which are not easy to <br /> detect by drivers. <br /> <br /> Effects <br /> <br /> Volumes. Little or no effect. <br /> <br />Speed. Drivers generally ignore posted <br />speed limits, and travel at speeds which the <br />drivers consider reasonable, com/ortable, <br />convenient and safe under existing condi- <br />tions. Drivers appear not to operate by the <br />speedometer, but by the conditions they <br />meet. A speed, limit! change accompanied by <br />enforcement may see a speed reduction (see <br />Chapter 2 on enforCement). <br /> <br />Traffic Noise, Air Quality and Energy Con- <br />sump~ion. Little or no effect. <br /> <br />Traffic Safety. Effects of speed limit changes <br />on traffic safety on local residential streets <br />have not been reported. <br /> <br />Community Reaction. If speed limit signs <br />posted are significantly lower than prevailing <br /> <br />SPEED <br />LIMIT <br /> <br />40 <br /> <br />SPEED <br />ZONE <br />AHEAD <br /> <br />SPEED <br />LIMIT <br /> <br />30 <br /> <br />traffic speed, residents normally place some <br />hope in them, or in subsequent enforcement. <br />However, ff the posted l/mits are within a few <br />miles per hour of the previously prevailing <br />traffic speed, they really don't address the <br />residents' problem. Since residents may feel <br />that speeds of 25 to 35 m.p.h, are too fast <br />(limits which are enforced on roughly 80% of <br />the residential streets in the United States), <br />the basic issue is not whether the signs are <br />effective, but the way in which the speed <br />limits themselves are set for local streets in the <br />United States. <br /> <br /> Cost <br /> <br />Minimal for a section of street. <br /> <br />Reference <br /> <br />Institute of Transportation Engineers, Residential Street Design <br />and Traffic Control <br /> <br />Neighborhood Traffic Control <br /> <br />January 1994 <br /> <br /> <br />