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HomeMy WebLinkAboutMINUTES - 06242003 - C.96 C.96 THE BOARD OF SUPFRVISOR.S OF CONTRA COSTA COUNTY, CALIFORNIA Adopted this Order on June 24, 2003 by the following vote: AYES: Supervisors Gioia, Uilkema, and Glover NOES: None ABSENT: Supervisor DeSaulnier ABSTAIN: None The Board of Supervisors ACCEPTED the Cummings Skyway/Crockett Boulevard Improvement Mitigation Study, as recommended by the County Administrator. I hereby certify that this is a true and correct copy of an action taken and entered on the minutes of the Board of Supervisors on the date shown. Attested:June 24,2003 John Sweeten,Clerk of the Board of Supervisors and County Administrator Byj � Deputy Clerk f 4 ED RUZAK G ASSOCIATES, INC. Mr. John Sweeten June 3, 2403 County Administrator WORK PRODUCT County of Contra Costa CONFIDENTIAL 651 Pine Street, 11 th Floor Martinez, California 94553-1229 Subject: Cummings Skyway/ Crockett Boulevard Improvement Mitigation Study Dear Mr. Sweeten:: This letter type report represents my independent evaluation of the Cummings Skyway/ Crockett Boulevard intersection, herein called "intersection". The report assesses some feasible mitigation considerations that could improve the safety and operation at the intersection. These include, but were not limited to, retaining the existing conditions, roadway improvements to vertical grade, horizontal and vertical alignment and sight distance; installation of traffic signals, installation or modification of existing signing and/or marking, truck traffic re-routing and warning controls and operational improvements to alert drivers of weather conditions. Also addressed is the potential for improving this location, while not considering similar mitigation at other intersections in hilly, foggy areas of Contra Costa County. STANDARDS DISCUSSION The cliche that "reasonable engineers can differ" is certainly true in traffic engineering since it is not an exact science. Further, many lay persons, including drivers, believe they have knowledge of what should be done at a particular intersection, based on their perception of the "danger" or " number of near misses". Whether founded or not, the traffic engineer must address the subject as well as proven guidelines and standards in the industry. 1 10061 Talbert Avenue, Suite 200 Fountain Valley, CA 92708 (714) 964-4880 FAX (714) 964-7219 2040 Palk Street, No. 343 San Francisco, CA 94109 (415) 929-8745 In traffic engineering for the subject intersection, there are two major sources of guidelines and standards that were considered. They include the California department of Transportation (Caltrans) Design and Traffic Manuals and the American Association of Mate Highway Transportation Officials (AASHTO), "A Policy on Geometric Design of Highways and Streets", 2001 . IDENTIFIED OR PERCEIVED PROBLEMS [wring the course of the Pespitro case the evaluation by either the plaintiffs expert or the defense expert expressed the following: 1 . The 55 mph posted speed was not acceptable for considering stopping sight distance (SSD) or corner sight distance (CSD) because the County's speed survey indicated an 85th percentile speed of 64 mph. Thus, values for SSD and CSD should have considered 65 mph criteria. 2. The present SSD of 700 feet is adequate for a 55 or 65 mph design and operating speed. 3. The present CSD of 700 feet is adequate for a 55 or 65mph design and operating speed for automobiles, but not for loaded or unloaded trucks. The trucks exposure and acceleration capabilities require a longer time to enter Cummings Skyway and this is dangerous to them and the users on Cummings Skyway. 4. Left turning trucks have a turning radius that doesn't totally place them within the southbound acceleration lane. They overlap into the southbound through lane. 5. The grade at the intersection, specifically for the Crockett Boulevard approach is not flat. When traffic turns left they must also accelerate up a grade of approximately 6% while a 3% grade is an acceptable AASHTO design. 6. The warning signs in advance of the intersection at 1200 and 700 feet were adequate. Their effectiveness in fog was questioned. 2 7. Fog considerations exacerbate the problem for Crockett Boulevard truck traffic and auto traffic. 8. Truck traffic from Crockett Boulevard is a major operations problem at this intersection. Thus, trucks should be re-routed from Crockett Boulevard. SIGNING The advance intersection warning signs on Cummings Skyway warn of the upcoming intersection. They are reasonable and in conformance with Caltrans Traffic Manual. Placing a flashing warning beacon on each of the signs would provide a better target value during night time and inclement weather. However, the research studies relative to a flashing beacon's ability to induce a reduction in roadway travel speed is such that very little speed reduction is accomplished. By adding beacons, one does not mitigate the fog problem, truck situation and CSD sight distance concerns. SIGHT DISTANCE The SSD and CSD for 65 mph traffic and for slow trucks emerging from Crockett Boulevard are limited by the topography and alignment of Cummings Skyway. The present SSD of 700 feet is adequate for a 55 or 65 mph design and operating speed. The present CSD of 700 feet is adequate for a 55 or 65mph design and operating speed for automobiles, but not for loaded or unloaded trucks. The trucks exposure and acceleration capabilities require a longer time to enter Cummings Skyway from Crockett Boulevard. 3 The time necessary for trucks to clear the intersection according to AA I-ATO guidelines is approximately 11.5 to 13.5 seconds. The latter time is because of the need to accelerate up the 0% grade. Thus, in theory at 55 mph (95 ft./second), one could argue that 1090 to 1280 feet of sight line would be needed. In order to physically obtain this distance the County would have to remove the large bank of earth to the west of Crockett Boulevard and most likely provide a retaining wall to hold back the vertical cut bank. This would be a very costly capital improvement project. If the bank was successfully removed to improve sight distance there is still the potential that a high speed Cummings Skyway traffic could strike an emerging truck coming from the STOP sign. MULTI-WAY STOP SIGN This mitigation measure was considered and rejected for the following reasons. 1. "It should ordinarily be used only where the volume of traffic on intersecting roads is approximately equal", status the Caltrans Traffic Manual policy. Cummings Skyway carried 7,870 vehicles per day in year 2002. Crockett Boulevard carried 2500 vpd. The imbalance is not conducive to multi-way STOP control 2. Rear end accident potential would increase on Cummings Skyway. 3. Drivers would not respect the unnecessary stops on Cummings Skyway and would "roll or run the STOP". This would further endanger the users on Crockett Boulevard who would assume that all traffic is going to stop. 4. There is not an accident problem as indicated by five or more reported collisions within a 12 month period that would be susceptible to correction by a multi-way stop control. 5. A traffic signal is warranted, but is not urgently needed at this location. Thus, the multi-way stop control should not be used as an interim measure. 4 TRAFFIC SIGNALIZATION Motor vehicle traffic counts taken in year 2002 do not satisfy the Caltrans two basic warrants for consideration of a traffic signal, the "Minimum Vehicular Volume" and the "Interruption of Continuous Traffic". The accident history warrant also does not indicate a minimum of 5 accidents correctable by a traffic signal. However, the Peak Hour Volume Warrant is met. This warrant states that, "the satisfaction of a warrant is not necessarily justification for a signal. Delay, congestion, confusion or other evidence of the need for right of way assignment must be shown". My evaluation of this intersection believes that the satisfaction of this warrant plus the following evidence would in effect allow the County's decision makers to install a traffic signal at the subject intersection. 1 . Six of the eight hours at this intersection satisfy the "Interruption of Continuous Traffic" warrant. 2. Fog reduces visibility to a level that it is difficult for traffic to exit Crockett Boulevard and enter Cummings safely. During these times the right of way assignment is not clear and one could consider confusion as a major part of how to operate in this environment. 3. The presence of large trucks attempting the aforementioned maneuver exacerbates the situation. 4. The traffic signal with proper advance signing and detection would clearly define the right of way. 5. The present delay and back up on Crockett Boulevard due to the time trucks need to take to clear the intersection would also be a factor that speaks for the need to have right of way control. 5 RE-ROUTE THE TRUCK TRAFFIC From the location of the major truck users in the area, including the sugar company and industrial refinery trucks it does not appear that a reasonable alternative routing is available. The terrain in the subject area is would require significant out of the way travel for the truck users. More important is my opinion that the private property owners and users would not wish to re-route their trucks from the shortest distance to and from their locations. CONCLUSIONS It is my opinion that signalization of the subject intersection is the most feasible improvement consideration. This must be done in conjunction with the installation of advance changeable message signing on Cummings Skyway. The signs would be "blank" when the signal shows green for Cummings Skyway and would flash "SIGNAL AHEAD PREPARE TO STOP" when Cummings Skyway turned to yellow and during the red phase. The signal would be fully actuated and would "dwell" in green for Cummings Skyway until Crockett Boulevard traffic goes over the advance loop detectors. With this signalization design and operation, the potential for rear end accidents should be minimized. The right angle accident potential would be significantly reduced or even eliminated. The Cummings Skyway signal timing with a sufficient yellow time and "all red" clearance interval should reduce the potential for vehicles running the red light and broadsiding the Crockett Boulevard emerging traffic. The problem with slow trucks entering traffic would be eliminated and the turning radius encroachment into the through lane of Cummings Skyway would not be a factor nor problem. There will always be a concern that this location was singled out because of a major collision and other locations throughout the County have similar conditions and should be treated the same. 6 I suggest that the County develop an inventory of locations with similar characteristics such as periodic fog, high true traffic, reduced sight Cines and difficult topography and terrain. A further review of the accident history would allow the County Traffic Engineer to prioritize these locations and determine if and when improvements should be considered. Respectfully submitted, Edward Ruza C CE 18824 RTE 0202 eummings.rpt