The City of Kingman receives numerous requests for traffic control signs, ranging from requests for four-way stop signs to children at play signs. There are a lot of misconceptions about the effectiveness of these signs.
The U.S. Secretary of Transportation, under authority granted by the Highway Safety Act of 1966, decreed that traffic control devices on all streets and highways open to public travel in accordance with 23 U.S.C 109(d) and 402(a) in each State shall be in substantial conformance with the Standards issued or endorsed by the Federal Highway Administration (FHWA).
The City of Kingman utilizes the Manual on Uniform Traffic Control Devices, published by U.S. Department of Transportation Federal Highway Administration, to determine when, where and how to post traffic control signs. Typically a "sign plan" is developed in conjunction with engineering design plans for major arterial and collector streets. In residential districts regulatory signs are evaluated in conjunction with the development of new subdivisions and/or based on traffic patterns. Requests for new signs or changing the existing signage is evaluated by the City's Traffic Safety Committee, utilizing the criteria found in the Manual on Uniform Traffic Control Devices.
Uniformity of devices simplifies the task of the road user because it aids in recognition and understanding, thereby reducing perception/reaction time. Uniformity assists road users, police officers, and traffic courts by giving everyone the same interpretation. Uniformity assists public highway officials through efficiency in manufacture, installation, maintenance, and administration. Uniformity means treating similar situations in a similar way. The use of uniform traffic control devices does not, it itself, constitute uniformity. A standard device used where it is not appropriate is as objectionable as a nonstandard device; in fact, this might be worse, because such misuse might result in disrespect at those locations where the devices is needed and appropriate.
Many requests are received for STOP signs to interrupt traffic, or to slow speeding vehicles. The Manual on Uniform Traffic Control Devices calls out that STOP signs should not be used for speed control. Studies in Arizona and across the country show that there is a high number of intentional violations when STOP signs are installed as speed breakers. There is a common belief that stop signs provide relief from traffic speeding problems. On the face, it would appear reasonable that when approaching a stop sign, motorists have to slow down. However, studies show that speeds within a block of the stop sign are either unaffected by the stop sign or , in some cases, actually increase. At the point of installation, speeds are reduced, but the effect on traffic approaching or leaving the controlled location is negligible. Some motorists actually increase their speed to make up for the inconvenience. Additional traffic noise also is associated with stopping and starting. Braking and acceleration increase tire noise and engine noise. Stop signs also increase the amount of time any one vehicle is at a particular point. Therefore, residents living near the stop controlled intersection will experience an increase in traffic noise.
STOP signs should never be used on the through highway or arterial. In determining where STOP signs should be used, an analysis of the intersection is conducted and reviewed by the Traffic Safety Committee. One or more of the following conditions must exist: (1) At the intersection of a less important road with a main road where application of the normal right-of-way rule is unduly hazardous. (2) On a street entering a through highway or street. (3) At an unsignalized intersection in a signalized area. (4) At other intersections where a combination of high speed, restricted view, and serious accident record indicates a need for control by the STOP sign.
Multiway (four-way) stop control can be useful as a safety measure at intersections if certain traffic conditions exist. Safety concerns associated with multiway stops include pedestrians, bicyclists, and all road users expecting other road users to stop. Multiway stop control is used where the volume of traffic on the intersecting roads is approximately equal. Typically multiway stops are not warranted unless the vehicular volume entering the intersection from the major street approaches (total of both approaches) averages at least 300 vehicles per hour for any 8 hours of an average day.
SPEED LIMIT SIGNS
A common myth is that posting a lower speed limit will cause drivers to slow down and will reduce accidents. Facts indicate otherwise. Research conducted throughout the country over several decades has shown that drivers are influenced by the type of street and the prevailing traffic conditions, and not the posted speed limit.
Arizona's Basic Speed Law (ARS '28-701) requires that: A person shall not drive a vehicle on a highway at a speed greater than is reasonable and prudent under the circumstances, conditions and actual and potential hazards then existing. A person shall control the speed of a vehicle as necessary to avoid colliding with any object, person, vehicle or other conveyance on, entering or adjacent to the highway in compliance with legal requirements and the duty of all persons to exercise reasonable care for the protection of others.
Except as otherwise posted any speed in excess of the following speeds is prima facie evidence that the speed is too great and therefore unreasonable: (1) Fifteen miles per hour approaching a school crossing. (2) Twenty-five miles per hour in a business or residential district. (3) Sixty-five miles per hour in other locations. (ARS 28-703)
The City has the authority to determine by an engineering and traffic investigation the proper and maximum speed for all arterial streets in its jurisdiction, that may be more or less than the maximum speed permitted by ARS 28-703. Speed limits between 25 and 55 mph may be established on the basis of traffic engineering surveys. These surveys include roadway conditions, roadway design speeds, accident records, and the prevailing speed of prudent drivers.
If an unreasonably low speed limit is posted, most drivers will ignore the signs, while a few may try to stay within the posted speed limit. This causes conflicts between faster and slower drivers, resulting in more accidents. Unrealistically low speed limits also increases the number of violators, and creates a bad image for the police and the community.
CHILDREN AT PLAY SIGNS
The City of Kingman does not provide "Children At Play" signs. These signs are not enforceable and provide a false sense of security for the parent and the child. Because of these serious concerns, Arizona law does not recognize "CHILDREN AT PLAY" signs.
The decision to install a traffic signal is based on an engineering study of traffic conditions, pedestrian characteristics, and physical characteristics of the location to determine whether installation of a traffic control signal is justified. A series of traffic signal warrants are conducted as part of this engineering analysis as follows:
Warrant 1 Eight-Hour Vehicular Volume
Warrant 2 Four-Hour Vehicular Volume
Warrant 3 Peak Hour Vehicular Volume
Warrant 4 Pedestrian Volume
Warrant 5 School Crossing
Warrant 6 Coordinated Signal System
Warrant 7 Crash Experience (both number and severity)
Warrant 8 Roadway Network
The satisfaction of a traffic signal warrant or warrants does not in itself require the installation of a traffic control signal. In addition to this information characteristics of the roadway and surrounding uses also need to be evaluated. Turning movements on and off of the roadway; the number of travel lanes and the presence of turn lanes; the posted or statutory speed limit or the 85th-percentile speed on the uncontrolled approaches; intersection geometrics; channelization; grades, sight-distance restrictions, transit stops and routes; parking conditions; pavement markings, roadway lighting, driveway locations; distance to nearest traffic control signals; utility poles and fixtures; and adjacent land use are some of the other factors that are evaluated.
A traffic control signal should not be installed unless one or more of the warrants are met, but should not necessarily be installed if the signal will not improve the overall safety and/or operation of the intersection or if it will seriously disrupt progressive traffic flow.
Traffic engineers compare existing conditions against standards established after many years of study throughout the country. Under these conditions a new signal will generally operate effectively. If established standards have not been met, congestion and motorist violations occur which cause more accidents. Traffic signals at collector and local street intersections improves access onto major streets, but can result in more neighborhood cut-through traffic.
A properly placed signal can improve the flow of traffic and decrease accidents. An unnecessary one can be the source of danger and annoyance to all who use the intersection, including pedestrians, bicyclists and motorists.