Agenda - Council - 05/26/1998 - Laserfiche WebLink

Home

! t Stop Signs I I A stop sign is one of our most valuable and effective traffic control devices... when used at the right place and under the right conditions. It seems so easy and inexpensive we can discourage unwanted traffic from using a street and control the speeds of the remaining traffic by simply installing a stop sign. At least that is what cities and counties are told da.ily by concerned residents. But does it really work, or is it just a symbol that really does not deter traffic? Or worse yet, does the stop sign create larger traffic problems? Stop signs have been installed and studied often so many of their benefits and detriments can be predicted for a particular location. A stop sign is one of our most valuable and effective traffic [' control devices... when used at the ,,- ..... :: right place and . :',- 'L*- - ~' under the right con- create a dangerous situation and diminish the effec- tiveness of other signs when improperly used. It is often assumed that installing a stop sign will slow traffic along a stretch of road. Unfor- tunately, overall speed may actually increase. A number of drivers are some what irritated by the installation of these "speed control stop signs" and develop a tendency to make up for lost time by over accelerating or by traveling study also showed that speeds ly actual reduction in speed appears to be within a few hundred feet of the stop sign itself. Residents near the stop sign, while seeing lower speeds, are faced with other new prob- lems. Decelerating and accelerating vehicles make more noise than those passing at a con- stant speed. Commercial vehicles, diesel engine vehicles, and those with exhaust prob- lems or modifications add significantly to the noise level when accelerating. There is also an air quality element associ- ated with vehicle stops. ]dot spots for air pollution in urban areas are generally at inter- sections with high volumes of idling traffic. Research has shown that 1,000 automobiles decelerating to a stop from 35 mph and then accelerating back again will increase carbon monoxide emission by 24 pounds, hydrocar- bons by 1.7 pounds and nitrogen oxide by 1.9 pounds. These quantities may be slightly high for new cars, but they represent the situation where only single cars are stopping. The stated cost of a stop sign may be mea- sured by its cost of approximately $50 to install. The true cost should reflect vehicle impacts. A single stop sign installed on a 25 mph street in a Wisconsin city was calculated by university engineers to increase annual fuel costs by 60,000 gallons or about $75,000 per year. Installing a stop sign or series of stop signs may divert some traffic from that street. Unfortunately, that traffic may be diverted to another street where ultimately the same demand for a stop sign may be made. Traffic may be diverted to secondary streets less able to safely carry the traffic volume. Studies have not been able to document any long term reduction in traffic caused by the simple installation of a stop sign. A final concern over installing a stop sign at an intersection with a low volume traffic on the cross street, or at a mid-block location, has to do with the effectiveness of the sign itself and its impact on other stop signs. A Michigan study showed that approximately half of the motorists made a rolling stop at the stop signs on local streets, and one-quarter of traffic did not stop at all. Observations throughout the St. Paul and Minneapolis metropolitan area have also shown a high volume of rolling stops at intersections where cross traffic conflicts are not anticipated. Accidents do occur with stop signs and accident rates can increase after installation of stop signs. When stop signs are requested to control speed or discourage traffic, the best approach may be to ana- lyze the problem and situation in detail and look for alternative solutions. ~ I I I I I I I I I I I I I I I I For additional "::':":;:':'";:" Transporlation ' Dt']lffl'[lllqlll ~ Ill I II1,~1'1'. ' I