2001-03-19 Special Called Regular Meeting and Public Hearing

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r I J . '. i ~ ~ e e c19 DEVICES FOR NEIGHBORHOOD TRAFFIC CONTROL 81 where the protected street is a major street (primarily in the United States). where sight distances approaching the intersection are substandard, and traffic approaching under the general rules regarding uncontrolled intersections would run a substantial risk of being involved in collisions. where there is a record of an accident pattern amenable to mitigation by right- of-way controls, yet conditions do not appear to justify requiring traffic on both streets to stop. Four-way Stop. This type of intersection control is more common in the United States than elsewhere. Intended primarily where two collector or major streets intersect and where funds for a traffic signal are not available, it has frequently been used in response to com- plaints by the public about excessive speeds with indifferent results. The unnecessary stop- ping of all vehicles adds to noise, fuel consumption, and emission of air pollutants-earbon monoxide, hydrocarbons, and oxides of nitrogen. , "'l' J~l 'jrii: . '~~' 1 j; . '.;;( ;:.j;.. . .~ '.' , ~ :- ~ !l Numerous studies have been prepared regarding the degree to which stop signs are I obeyed. Generally, when not required to stop by cross traffic, only 5 to 20 percent of all: .~ drivers will come to a complete stop, 40 to 60 percent will come to a "rolling" stop below t ,5 IE-ph ~8 km/h), and 20 to 40 percent will pass through at higher speeds. Signs placed on ,r majofand coUectorstreiiS1or'iliepiiij)ose ofspeeareaiicuon arelliemosfflagrantIfviO~------ -- --~-; lated. Thus, stop signs which do not meet the standard warrants tend to some extent to be ignored by drivers, whereas signs placed for right-of-way purposes are more likely to be obeyed. . a. Effect on Traffic Volume. Where local streets offer significant savings in time over congested parallel major and collector routes or allow avoidance of congestion points, stop signs will do little to reduce traffic volume. But when the local street offers marginal travel time advantage over other routes, the time lost at stop signs may be enough to shift traffic. ~ b. Effect on Traffic Speed. Requests from citizens for ins~lation of stop signs are usually related to desire for speed control. The general conclusion from numerous studies on effectiveness of stop signs as a speed control measUre is that they have liule overall ef- fect on speed, except \\,ithin approximately 200 feet (60 meters) of the intersection con- trolled. They are almost ~niversally reported to have little or no effectiveness in controlling mean or 85th percentile speeds at midblock. A possible reason why resident beliefs about the speed control effectiveness of stop signs is contrary to the findings of engineering studies is that there is some evidence that stop signs do reduce themidblock speed of the, fastest vehicles in the traffic stream. It is probably these fastest vehicles, rather than those traveling at the median or 85th percentile speed, that disturb residents. Elimination of ex- treme speeding by the few very fastest vehicles could satisfy the residents' concerns without altering the 85th percentile or median speeds at all. Another reason why neighbors may feel stop signs to be an effective speed control device is that they perceive traffic slowing down and stopping at the controlled intersec- tion as a real benefit; regardless of what effect the signs have on midblock speeds. Pedestrians are trained to cross at intersections; so a measure which reduces speeds and creates gaps inthe vehicle stream there can logically be thought practical. Hence, engineer- ing studies which have found stop signs ineffective for residential area speed control may have considered an irrelevant data base. ''I!, c. Effect on Traffic Noise. Air Quality. and Energy Consumption. Stop signs tend to increase noise in the vicinity of an intersection by adding acceleration and braking noise. Deceleration, idling, and acceleration increase air pollutant emissions and fuel consump- tion; carbon monoxide, in particular, has an adverse impact on the immediate vicinity of its emission. ._L. _.__._ _._._".". c:: % <! ,... %I' u:= 3: ~. - ... -" , -e; '=-: ;:;zJ .~