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G r•h rt rt w r• rt (D rd o ro G O rt ri r• rt rt rt m H cn rt r o vo N� Eg nwwn xwrn 10 w Oo 0 rt oGo rt (DPs ron � (DP riro a (D CoH(D P y o n b w rt ((DD o m n m H r• d w rt P, r• n r• al r• a r Fl n o n P w oo m a m n rr (Drmr ((DD 'd H b Nroi 6 rt a rt 0 r• (D ro ri 0 m n G w rt n n H. rt 14 C) 0 n r• H ro ro rt Fl- oc r7 w rt ro ~TOP $i~n Compliance When STOP signs have been installed without good reason, motorists tend to ignore them. Three behaviors were observed in this survey: complete stop, rolling stop, and "through" (did not slow down or look). There was a higher compliance with the STOP sign at Ironwood than at Irving, in that 54% of the cars stopped completely at Ironwood, while only 32% stopped at Irving. However, 12% of all motorists did not slow down or look at either intersection. To compare STOP sign compliance, TJKM conducted the same study at an intersection where STOP signs are definitely warranted - Village Parkway and Brighton Drive. The percentage of complete stops - 67% - is about 10% better than the best compliance on Donohue; even more significant is the fact that only 1% of motorists ran through the warranted signs. Other Factor~ Three other results of STOP sign installation are more intangible: increased noise levels, increased air pollution, and increased fuel consumption. Before and after conditions of noise and pollution levels were not measured in this survey but should always be considered when evaluating ALL-WAY STOP signs. TJKM has included an article from a publication of the Western District Institute of Transportation Engineers which addresses and quantifies the pollution factor. Dublin Police Services has incurred some problems in enforcing the speed limit due to the location of the STOP signs. Because it is difficult to visualize the problem, Staff suggested that members of the City Council contact the Police Department to arrange to ride with Officer Atkinson prior to this March 23rd meeting. For the benefit of those who were unable to do so, as well as for benefit of the public, Officer Atkinson is prepared to demonstrate the enforcement problem at the meeting by means of visual aids. Summary and Recommendation The before and after studies indicate that STOP signs did not effectively reduce the speeds along Donohue Drive. Traffic volumes remained virtually the same. The accident history before and after the study is not conclusive, as the accidents did not occur near the intersections where STOP signs were placed. A significant factor is the lack of compliance with the new STOP signs, as only 54% of motorists complied with the STOP signs at Ironwood Drive and only 32% complied with the STOP signs at Irving Way. At both intersections, 12% of motorists did not glow down or look for opposing traffic. Additional adverse effects are increases in noise and air pollution, as well as the problems incurred in enforcing the speed limit. Staff recommends that the City Council consider the statistics contained in this report, not only as they apply to Donohue Drive, but also as they may apply to other requests for STOP signs to be presented at this March 23rd meeting and in the future. -2- MEMORA,NDUM 4637 Chabot Drive, Suite 214 Pleasanton Ca. 94566 (415) 463-0611 DATE: March 13, 1987 TO: Lee Thompson, City Engineer City of Dublin FROM_: SUBJECT: Ty Tekawa Follow-up Study - STOP Sign Installations on Donohue Drive at Irving Way and at Ironwood Drive At its meeting on September 8, 1987, the City Council voted to install STOP signs on Donohue Drive at Ironwood Drive and at Irving Way. The Council also requested a review of the effectiveness of the installations after six months. This memo describes the follow-up study after the STOP sign installations. Introduction In response to a petition requesting STOP signs to reduce speeds on Donohue Drive ~__~-~,"~-d~'l~e ~3-~n~TJKM conducted a traffic St~uY.u sTth~2~eSl;l~; Of T~h;: study were contMne-'h-~'W'i'fi--a memorandum to you dated g , . study included a radar speed survey, traffic counts, a review of accident history, citation experience and a field review. As a result of the study, TJKM recommended against the installation of STOP signs. The statement in that study was "STOP signs used for speed control are ineffective." Multi-way (3 or 4-way) STOP installations are installed to assign right-of-way at intersections with heavier traffic volumes than the volumes on Donohue Drive and its cross streets. TJKM recommended increased enforcement and the installation of raised reflective pavement markers. On August 11, 1986, the City Council asked [or a review of the August 22, 1985 Donohue Drive Study. That review was to be presented at the Council's August 25, 1986 meeting. At that meeting, TJKM reiterated the recommendation against STOP sign installations. The subject was continued to the September 8th meeting in order to give residents an opportunity to respond. At the September 8, 1986 meeting, the Council ordered that STOP signs be installed on Donohue Drive at its intersections with Irving Way and Ironwood Drive. The signs were installed on October 13, 1986, thus making both of the "T" intersections 3-way stops. TJKM's recommendation remained unchanged since the August 22, 1985 memo. The raised markers were not installed because of objections to the noise created when motorists drive over them. The fact that STOP signs also increase noise levels seems to have been ignored. Study Procedure To evaluate their effectiveness, TJKM repeated several of the studies performed before the STOP signs were installed. The "after" studies performed were a radar speed survey, a 24-hour traffic count, and a review of accidents. An additional study was a recording of the compliance to the new STOP sign installations. In each case, except for STOP sign compliance, the "after" data was compared to the PLEASANTON · SACRAMENTO · FRESNO · CONCORD Mr. Lee Thompson -2- March 13, 1987 August 25, 1985 study results to assess effectiveness. To compare compliance to the STOP sign installation, the results of the "after" study were compared to a study at an intersection where STOP signs are warranted. Radar Speed Survey Before and After Study Results As the following table shows, the installation of the STOP signs had very little effect on the 50th and 85th percentile speeds along Donohue Drive. The location of the two speed surveys (before and after the STOP sign installations) was the area between Ironwood Drive and Irving Way. RADAR SPEED SURVEY 50th Percentile 85th Percentile N B S._$_B N B S.__~B Before Installation After Installation 33 31 37 37 31 31 37 35 As shown by this table there has been no significant change in traffic speeds as a result of the STOP sign installations. Accident History There were a total of eight accidents reported on Donohue Drive from January 1984 to October 13, 1986. Four of the eight accidents involved parked cars, one was a rear-end collision, one a side-swipe, one a broadside accident and one a head-on, auto-bike accident. The latter two accidents resulted in injury. None of these accidents occurred at the intersections where STOP signs were installed. In the five months after the installation of the STOP signs, one accident has been reported. This accident was a single vehicle colliding with a fixed object. This accident also occurred at a location away from the STOP sign installations. No one was injured. . The attached Table I summarizes the accidents which occurred before and after the STOP sign installations. Pro-rating the accidents to a six month period results in a rate of 1.4 accidents/six months before the STOP sign installations and one accident/six months after the STOP sign installations. There appears to be no correlation between the accident occurrences and the STOP sign installations. STOP Sign Compliance A survey of the compliance to the new STOP sign installations at Irving Way and Ironwood Drive was conducted on January 23, 1987. Three behaviors were observed and tabulated: 1) A complete stop (rear end of car dips after braking), 2) A rolling stop (rear end does not dip after braking), 3) Through (car does not slow down or look carefully). The following table shows the percent of vehicles observed for each behavior: Mr. Lee Thompson -3- March 13, 1987 STOP SIGN COMPLIANCE Complete Rolling Location Stot~ ' Stor> Through Irving Way 32% 56% 12% Ironwood Drive 54% 34% 12% The table shows that there is a higher compliance to the STOP sign at Ironwood Drive than at Irving Way. The implication is that the STOP sign at Ironwood Drive is probably closer to being warranted than the sign at Irving Way. There is, however, a relatively high percentage (12 percent) of vehicles that did not even slow down or look carefully at the STOP signs at either location. To compare STOP sign compliance, TJKM conducted the same study at a STOP sign location where traffic volumes and the need for the assignment of right-of- way warranted the installation of 4-way stops. This location is the intersection of Village Parkway and Brighton Drive. The table below shows the compliance to the STOP signs on Village Parkway (northbound and southbound). STOP SIGN COMPLIANCE Complete Rolling Location Stop Stop Through Village Parkway at Brighton Drive 67% 32% 1% The percentage of complete stops at Village Parkway/Brighton Drive is about 10 percent better than the best compliance on the STOP signs on Donohue Drive. A more significant statistic is the percentage of motorists that ran through the STOP signs. Only I percent of the surveyed vehicles ran through the warranted signs, while 12 percent ran through the unwarranted signs. There are three other results of the STOP sign'installation which are slightly more intangible: increased noise levels, increased air pollution, and increased fuel consumption. Although the before and after conditions of noise levels and air pollutants were not measured, we feel that these non-traffic related impacts should be considered when evaluating the overall impacts of the ALL-WAY STOP signs. Summary of Findings The before and after studies indicate that the installation of STOP signs on Donohue Drive did not effectively reduce the speeds along Donohue Drive. Traffic volumes along Donohue Drive remained virtually the same. The accident history before and after the study was not conclusive. The accidents did not occur near either of the intersections where the STOP signs were installed. A significant finding of the study was the compliance to the new STOP signs. The STOP sign installation at Ironwood Drive showed that 54 percent of the traffic came to a full stop while only 32 percent complied at Irving Way. At both of the intersections, 12 percent of the vehicles did not slow down or look both ways carefully. When compared to a warranted installation the compliance at the STOP signs on Donohue Drive is poor. The intersection of Village Parkway and Brighton Drive, which is warranted, shows a 67 percent compliance and only 1 percent go through the signs. TABLE I DONOHUE DRIVE ACCIDENTS BEFORE STOP SIGN Location At Hillrose Drive 100' W/O Ironwood Dr. 39' S/O Irving Way 90' S/O Irving Way At Landaie Drive At 7573 Donohue Drive 326' N/O Irving Way At Gardella Drive 124' N/O Amador Valley Blvd. Date Time Type 2/25 13:00 rear-end 194~ 1/4 01:45 rear-end 2/8 21:50 sideswipe 3/19 01:50 sideswipe (parked) 9/10 20:00 sideswipe (parked) 1/9 01:50 rear-end (parked) 1/23 11:15 broadside 8/20 14:25 head-on AFTER STOP SICN (10/13/86) 1986 10/20 12:05 hit object Iniur~ no no no no no no yes yes no Gause drunk driver unsafe speed drunk driving unsafe speed unsafe turning movement hit and run failing yield auto-bike on wrong side of the road drunk driving Mr. Lee Thompson -4- March 13, 1987 An adverse side effect of STOP sign installations when they are installed to control speeds is the problem of enforcement. The traffic officer must station himself away from the intersection and clocl~ vehicles from difficult locations. By the time he clocks a violator, he is too far away to safely give chase in a residential area. Several studies have been cited in the past to discourage the use of STOP signs as a speed control device. As previously mentioned, one adverse effect of unwarranted STOP signs is the noise created by decelerating and accelerating vehicles. STOP signs also increase air pollution and decrease fuel efficiency. Attached is a recent article published in the Western District newsletter of the Institute of Transportation Engineers. This article quantifies the adverse effects of STOP signs on air quality and fuel consumption. Although the additional fuel consumption and air pollution resulting from stopping a single automobile may seem insignificant, the cumulative effect of stopping over 1,000 cars a day at several locations is measurable and can adversely effect positive trends towards increasing fuel efficiency and reducing air pollutants. nlc Attachment 157-001 · ' ~_ FEBRUARY 1987 XXX NO. 1 ~.'.-~'~ · Official Publication of the Western District Institute of Transportation Engineers TH STOP,-Si'GN' PI U lVil bY Wolfgang S. Homberger, Assistant Director, UC Berkley .' Institute of TransPortation Studies, Berkley, CA ':'. .-:' '. '.' -..., ,. - - .., . -.- -.. ' 'What is to be done aboutthe STOP These quantities may be slightly daily traffic (ADT) per direction by sign epidemic, if anything, and why? That there is an uncontrolled spread of STOP signs need not be explained to the readership of WesternlTE. Despite the formulation of warrants for the use of such signs, all too often political pressures have prevailed. (We have, of course, similar problems with other traffic controls.) One can understand and, perhaps, sympathize with politi- cians overruling engineers, but the results are deplorable nevertheless. In the past, the principal argument against the use of unneeded STOP signs has been the concept of control device uniformity. The same sign, used to mark a location where a full stop is vitally needed to prevent right-angle collisions, should not be used at other places where motorists are not faced with any unusual or unexpected con- flicts. Once the STOP sign seems to imply a nuisance regulation, observ- ance deteriorates and safety at danger- ous locations becomes compromised. However, a stronger argument rec- ommended for your consideration relates to increases in air pollution and fuel consumption. Past research has shown that the following increases .result per 1,000 automobiles decel- erating to a stop and then accelerating again: Cartxm monoxide (CO) emission Hydrocarbon (HC) emis.No~ Nitrogen oxide (NOx) Fuel consumption From 25 mph From 35 mph 13 lbs 24 lbs 5.8 gale 8.7 ga~s high for new cars now coming off the assembly lines. However, they repre- sent only the situation of single cars stopping in an approach. When queues build up in an approach, and cars have to move up in the queue one car length at a time, emissions and fuel consump- tion increase with the queue length- one car joining a 1 O-vehicle long queue will emit and consume 10 times as much of the above listed quantities than it would if arriving directly at the STOP sign. "' : ' The most distressing trend noted by this observer' and others has been the placement of all-way STOP signs at the intersection of arterials with minor cross streets. Queues build up quickly on the arterial with the magnified adverse effects just discussed. But what does this mean to the local politician facing insistent demands from the voters for more STOP signs; or what does it mean to these voters? The most significant deleterious effect is the CO emission which remains in the vicinity and can, under certain cli- matic conditions, seep into adjacent buildings or be sucked into air condi- tioner intakes. One hundred parts per million of CO in the air can cause slight headaches, twice this amount can lead to shortness of breath after moderate exertion, and three times this quantity can result in severe headaches, dizzi- ness, nausea, and other unpleasant symptoms. Residents living upstream of STOP signs at which queues develop should be made aware of these risks. This writer once was able to abort a proposed STOP sign installa- tion against flows of 10,000 average pointing out that one of the buildings~ adjacent to the site was a hospitall Increases in HC and NOx emissions are of regional concern. Here the prOb- lem is to try to persuade local groups'of.. the regional good. If the accumulated emissions from many 'Unwarranted STOP signs bring permissible air basin levels of these pollutants above EPA- mandated standards, then the regi°n may lose federal funds and be subject. to other sanctions..'""!.*', ;..:-~... As we have Seen in the last dozen years, increased fuel consumption become~ an issue only when petro- leum prices are high and supplies are Iow. At the moment, neither of these' conditions prevail and the argument Of fuel waste seems unpersuasive. How::' ever, no one doubts that therb will be ' higher pdces and restricted supplies in the future. '?'~i. :'.'.!: .'..-~':'.~;¥,.i' i:,:. . Traffic en~iir~;~rs"m~Y"~el'l'fb;i'i~;Ud trated. The air pollution and fuel con- sumption reductions we are able to make by such good traffic engineering practice as timing traffic signals more efficiently (as in California's FETSIM project) may well be going up in smoke at unwarranted STOP signs. Both as individuals and, for greater impact, in groups-perhaps through committees at the Section and Nati9nal levels of ITE-- we must marshal exper- tise to develop stronger arguments against unnecessary STOP signs. The more mature politicians may, in ..fact;- welcome our help in resisting Unreal- istic requests from voters. Let us help them, ourselves, and the society at large. _. , .: Date: To: From: Subject: March 10, 1987 City Council City Engineer Stop Sign Warrants MEMORANDUM The City has been receiving an increasing number of requests for speed controls, typically in the form of requests for stop signs. Because you are being asked to make decisions on this issue, Staff felt it might be helpful to further explain the Traffic Engineers' criteria and how they are used to determine the need for stop signs. Most of the general public do not realize that stop signs are not an effective speed control device. Speeds do decrease in the immediate vicinity of the stop signs; however, the speeds do not change between the signs. In addition, both noise and pollution increase due to the deceleration and acceleration of the vehicles. When the stop signs have been installed without a good reason, motorists tend to ignore them. This, in turn, causes a dangerous condition when drivers obeying the signs expect other drivers to stop and they don't. Drivers tend to obey stop signs when they perceive a need for the signs to establish the right-of-way. This situation typically occurs at locations of high traffic volume in both directions for four-way stops and for stopping minor movements at heavily traveled streets. Sight distance and traffic accidents can also enter into the perceived reasons for establishment of right-of-way. Attached are copies of the warrants developed by TJKM for establishing two-way and four-way stop intersections, for use in u~ban areas and modified for use in residential neighborhoods. Also included is a comparison of TJKM's warrants for four-way stops to those used by Alameda County and Contra Costa County. The City Council agenda for March 23rd includes four items relating to stop signs and speed studies. Staff has received other requests that will be presented at subsequent meetings. In addition to the information contained in this memo and its attachments, Staff suggests that each of you schedule a time prior to the meeting of March 23rd to ride with the City's Traffic Officer, Dennis Atkinson, to see first- hand the problems he has incurred in enforcing the speed limit and compliance with non-warranted stop signs. If you have any questions regarding this information, please feel free to call my office. LST/gr Attachments CiTY OFFICES 6500 DUBLIN BLVD. ADMINISTRATION 829-4600 BUILDING INSPECTION 829~)822 CItY COUNCIL 829-4600 CODE ENFORCEMENT 829~)822 ENGINEERING 829-4927 FINANCE 829-6226 PLA N NI NG 829-4916 POLICE 829~:)566 PUBLIC WORKS 829-4927 RECREATION 829-4932 CITY OF DUBLIN P.O. bOX 2340 DUBLIn, CALIFORNia 94568 "NOTICE OF PUBLIC HEARING March 10, 1987 The City Council of the City of Dublin will hold a public hearing regarding the following traffic-related issues: Review of Donohue Drive STOP Signs Approximately six months ago, the City installed STOP signs on Donohue Drive at the intersections of Ironwood Drive and Irving Way. At the time the City Council approved this installation, Staff was directed to review the effect of the STOP signs in six months' time and present a report to the City Council. This report will include the following items: a speed study, a volume study, an accounting of any accidents which may have occurred, and a STOP sign compliance study. In addition, the police department will give a presentation regarding enforcement. Vomac Road Study At the time that the original Donohue Drive study was presented, a resident requested that a similar study regarding speeding and possible solutions be performed on Vomac Road between Landale Avenue and San Ramon Road. The City's traffic engineering firm, TJKM, is performing the study and will present a report. Tamarack Drive Residents of the Tamarack Drive area requested that STOP signs be installed on Tamarack at the intersection of Burton Street (at Frederiksen School) and at the intersection of Brighton D3ive. While the TJKM's initial study of the Burton Street intersection indicated that the warrants for a three-way STOP intersection had not been met, the City has already installed additional school signs and replaced part of the No Parking zone with a Passenger Loading zone in front of the school to mitigate traffic congestion. At the City Council's request, TJKM has performed a subsequent study of the Burton intersection and also the Brighton Drive intersection (east end) and will present their findings. Bristol Road at Larkdale Drive STOP signs were recently installed on Larkdale Drive at the intersection of Bristol Road, replacing existing Yield signs. Residents of this neighborhood have requested that the City consider installing STOP signs on Bristol Road also (creating a four-way STOP). TJKM has made a study of this intersection and will present a report. This hearing will be held at the regular City Council meeting of March 23, 1987, at 7:30 p.m. at the Dublin Library Meeting Room and will take the form of a study session, at which the City Council will receive Staff's findings, take testimony from the public, and give Staff direction regarding action deemed necessary at these locations. We encourage you to attend this.hearing and provide any input you may have. If you have any questions, please feel free to call the office of the City Engineer at 829-4927. FI ~'RE 1 WARRANTS FOR ~VO-WAY STOP SIGN INSTALLATION Stop sign installation may be considered if any TWO of the following conditions exist: VOLUME (a) Total vehicular volume on the major street must be SOO vehicles per day or SO vehicles per hour during the peak hour on an average day. (b) Total vehicular volume on the minor street must be 2S0 vehicles per day Or 2S vehicles per hour during the peak hour on an average day. ACCIDENTS Two or more of types susceptible of correction by stop signs within a 12-month period. Yield sign to be considered if no other warrant is met. 3. VISIBILITY Critical approach speeds less than 15 mph. 4. U~N]JSUAL CONDITIONS Where 8S-percentile speeds greater than 25 mph prevail or where unusual conditions exist (such as school, playground, steep hill, etc.) ,Stop sign installation may be considered if any ONE of the following conditions exist: VOLU~ (a) Total vehicular volume on the major street must be 1,000 vehicles per day or 100 vehicles per hour during the peak hour on an average day. (b) Total vehicular volume on the minor street must be 500 vehicles per day or 50 vehicles per hour during the peak hour on an average day. ACCIDENTS Four or more of types susceptible of correction by stop signs within a 12-month period. 3. VISIBILITY Critical approach speeds of 10 mph or less. Reprinted from a Report by H. Richard bRtchell Traffic Engineer Concord, California 8 FIGURE 2 WARRANTS FOR FCO]t-WAY STOP SIGN INSTALLATION Four-way stop sign installation nmy be considered if any of the following conditions exist: VOLUME (a) Total vehicular volume entering the intersection from all approaches must average 300 per hour for any 8 hours of am average day. (24-hour equivalent approxinmtely 4,000 vehicles.) (b) In addition, the vehicular volume entering the intersection from the minor street or streets for the same 8 hours must average at least 1/3 of the total volume entering the inter- section (100 per hour min.). ACCIDENTS Five ore more of types susceptible of correction by stop signs within a 12-month period, with satisfactory observance and en- forcement of less restrictive control. VISIBILITY The straight line sight distance on one or more approaches of the major street for vehicles or pedestrians crossing the inter- section is less than 160 feet. RESIDENTIAL AREA Volume warrants to be reduced to 60% of the values above if ALL of the following conditions are met: (a) Both streets have residentiab frontage with existing 2S mph speed limits. (b) Neither street is an adopted through street. (c) Neither street exceeds 40 feet of roadway width. (d) No existing stop sign or signal is located on the more heavily traveled street within a distance of 800 feet. (e) Intersection has four legs, with streets extending 800 feet or more away from the intersection on at least three sides. (f) Installation of a four-way stop is compatable with overall traffic circulation needs for the residential area. Reprinted from a Report by H. Richard Mitchell Traffic Engineer Concord, California 9 FOUR-WAY STOP SIGN WARRANTS TJKM' s Alameda Co. Contra Costa Co. VOLUME A. Major Street B. Minor Street 300/hr. for any 8 hrs. 1/3 of total volume (100/ hr. minimum. 500/hr. for 8 hr. period.* 200/hr. for 8 hr. period* 750/day; volume for each leg of intersection to be approx, equal; in no case greater 2:1. Alameda Co. volume warrants include pedestrians as well as vehicles. ACCIDENTS Within a 12-mo. period, of type correctable by STOP signs VISIBILITY Minimum straight-line sight distance AVERAGE APPROACH SPEED 5 160 ft. 5 (not addressed by either County - see average approach speed) If approach speed exceeds 40 mph, reduce volume warrants to 70% of above. 30 mph RESIDENTIAL AREA (addressed by TJKM only) Reduce volume warrants to 60% of above if ALL of the following conditions are met: (a) Both streets with residential frontage & existing 25 mph speed limit. (b) Neither street is an adopted through street. (c) Neither street exceeds 40 ft. in width. (d) No existing STOP sign or signal is located on the more heavily traveled street within a distance of 800 feet. (e) Intersection has 4 legs, with streets extending 800 ft. or more away from the intersection on at least 3 sides. (f) Installation of 4-way STOP is compatible with overall traffic circulation needs for the residential area'. Paint "STOP AHEAD" / f'- ~ \ /And "STOP" (2 Places) nt' STOP" CITY OF DUBLIN STOP SIGN INSTALLATIONS o, ~o,o,u~ ~,.. ~, ,,o,woo~ ~,. AND AT IRVING WY.-