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What Are Traffic Control Devices Traffic Engineering Project Public Works Department Traffic Control devices are all signs, signals, markings, and devices placed on or adjacent to a street or highway by a public body having the authority to regulate, warn or guide traffic. What Is Meant By Uniformity of Traffic Control Devices? Uniformity means treating similar situations in the same way. This simplifies the task of the driver because it aids in instant recognition and understanding. Uniformity aids police, courts and road users by giving everyone the same interpretation. It aids public highway officials through economy in manufacturing, installation, maintenance, and administration. The Manual on Uniform Traffic Control Devices is the publication that sets forth the basic principles which govern the design and usage of traffic control devices. The Manual was prepared by a National committee which included state, county, and municipal representation. The standards in this Manual with certain exceptions apply to all streets and highways regardless of the governmental agency having jurisdiction. How Are Speed Limits Determined? Legal speed limits are established by law and may be changed only when justified on the basis of an engineering study. A widely accepted principle is to set speed limits as near as practicable to the speed below which 85% of the vehicles are traveling on the highway. Experience has shown that approximately 85% of the motorists drive at a speed that is reasonable and prudent. Speed limits thus established encourage voluntary compliance because they appear reasonable to the public. Those 15% of drivers who will not comply with reasonable speed limits are the drivers who are subject to enforcement action. What Effect Do Posted Speed Limits Have On Actual Traffic Speeds? Very little effect. There is a common belief among laymen, and even by some officials, that the mere posting of speed limit signs will cause drivers to react accordingly. This is not true and is why posted speed limits must be realistic to receive compliance. Unrealistically low speed limits will invite violation by responsible drivers. Enforcement of unreasonably low limits sets up the so-called "speed trap" that results in poor public relations. The posting of proper speed limits has the beneficial effects of smoothing traffic flow and aiding effective law enforcement. When Should Traffic Signals Be Installed? Traffic signals should be installed when they will alleviate more problems than they will create. This must be determined on the basis of an engineering study. A warranted traffic signal which is properly located and operated may provide for more orderly movement of traffic, and may reduce the occurrence of certain types of accidents. On the other hand, an unwarranted traffic signal can result in increased delay, congestion, and accidents. Many people seem to believe that traffic signals are the answer to all traffic problems at intersections. If this were true, no traffic engineer in his right mind would deny a request for a signal. However, a traffic signal only functions by stopping traffic, and any time a motor vehicle is stopped in the road a potential accident is created. It does not matter whether the stop is caused by a flat tire, a left turn into a driveway, or by a traffic signal - the possibility exists that the motorist who is following will not notice the stopped vehicle until it is too late. What traveler has not experienced that sickening feeling that occurs when a traffic signal suddenly turns amber a few hundred feet in front of him? Who has not experienced the aggravating hopelessness of waiting in a long line of cars for a traffic signal to change, moving ahead a few feet, and then having the signal turn red again? The need for traffic signals should be based on a competent engineering study. What Is The Primary Purpose Of Guide Signs? The principal purpose of guide signs is to direct travelers to their destinations by the best route. However, it is not feasible to install signs listing all of the possible destinations that may be reached from the highway. Drivers must be expected to make reasonable preparation for locating their destination and to have information that is readily available on road maps. How Are Guide Sign Messages Determined? Simplicity and clarity are necessary because drivers of moving vehicles are unable to read lengthy or complicated messages on signs. For this reason, the number of lines on a sign is kept to a minimum, and should not exceed three. On freeways, high traffic speeds demand that the number of signs be limited to absolutely essential for the guidance of the motorist. Freeway exits are identified by exit number, the route number or by the name of the intersecting road. Certain additional messages may be provided where justified. In rural areas signs may be installed to direct travelers to services such as roadside rests, gas, food, and lodging.  |
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