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CASE # REQUEST FOR THREE-WAY STOP AT 142ND LANE AND TUNGSTEN STREET By: Steve Jankowski, City Engineer Background: On March 27, 1998, the City received a letter, along with a petition signed by 24 neighborhood property owners and residents, from Mrs. Tracy Kremer of 14270 Tungsten Street, requesting an all-way stop (three-legged intersection), at the intersect'ion of 142nd Avenue and Tungsten Street. Mrs. Kremer's letter states that vehicles travel consistently at a higher rate of speed than the posted limit of 30 mile per hour (mph), and that the intersection of 142nd Lane has a blind spot to the south. Observations: The City's Public Safety Aide, Laurie Swadner, conducted a speed study on March 31, 1998, and on April 1, 1998. Copies of the results of these studies are attached. The April 1, 1998, study should be viewed rather than the March 31 date, since the streets were wet on that date and traffic should have been traveling slower than usual. The April 1 study does show 15 of 69 vehicles exceeding the 30 mph limit, however, only five of these 15 exceeded the limit by more than two miles per hour with the maximum speed observed being 37 mph. On April 8, Ms. Swadner, located in a vehicle near the petitioner's drive at 14270 Tungsten Street, timed the interval when a northbound vehicle on Tungsten could first be seen and the time it passed her location. Attached is the raw data on her analysis. The interval of reaction time ranges from three seconds from a car traveling 39 mph to 10 seconds for vehicles traveling well under the limit. It is significant to note the different reaction times associated with the same speeds. This is explained by the fact that many motorists slow down when they observe a potential conflict, such as a parked vehicle or pedestrian or child. On the other hand, the vehicle traveling 39 mph, blatantly in excess of the speed limit, did very little to modify its speed, leaving a very short reaction interval. Discussion: The Traffic Review Committee, consisting of Director of Public Works Dean Kapler, Police Chief David Gustafson, and City Engineer Steve Jankowski, observed the site together on April 14. The Committee observed the visibility of Tungsten Street from both the intersection of 142nd Lane and the driveway at 14270 Tungsten. With a City vehicle traveling a near constant speed of 30 mph, a reaction time was noted of between seven to nine seconds at both the intersection and the driveway. A reaction time of 10 or more seconds is considered desirable. In reviewing the accident history for the intersection, there have been no accidents reported to the City's Police Department for years 1993 through 1997. A review of the speed study indicates that some speeding over the posted 30 mph limit is occurring. When evaluating speeds, traffic engineers define the speeds at which 85% of the traffic is traveling as a safe and prudent speed. The speed survey shows that the 85th percentile speed of northbound traffic is 31.6 mph, while that of the southbound traffic is 28 mph. Ten percent of the traffic is traveling at a speed more than two miles per hour over the speed limit. There are three warrant criteria for the placement of an all-way stop. (1) Traffic signals are warranted but cannot be immediately installed. This is not the case in this location. (2) An accident problem of five or more accidents corrected by a stop sign in a 12 month period. This