Review Pedestrian Safety Concerns at Variolite St and 161st Ave

At the April 18th Public Works Committee meeting staff was directed to gather traffic data and other pertinent information regarding pedestrian safety at the intersection of Variolite St/ 161st Ave.  Staff has compiled traffic counts, speed data, stopping sight distances for vehicles, pedestrian sight distances, accident reports and LOS  (Level of Service) ratings for the intersection.  Variolite St  has a posted speed limit of 50 mph with a restricted sight line view to the north of 161st  because of a hill.  Information gathered from the police speed trailer over two days shows the 85 percentile speed is 64.91 mph. The speed limit is commonly set at or below the 85th percentile operating speed (being the speed which no more than 15% of traffic is exceeding) and in the US is typically set 8 to 12 mph (13 to 19 km/h) below that speed.

15-20 minutes




 

 

The results of information gathered are as follows:
Traffic Counts (traffic counts are based on two 24 hour counts and then averaged)
Variolite St south of 161st Ave =1767 cars
Variolite St north of 161st Ave=1817 cars
161st Ave west of Variolite St=674 cars
161st Ave east of Variolite St= 522 cars
Crosswalk Width on Variolite St= 52 feet
Level of Service Rating-A  Average wait time is estimated at 4.3 seconds
Clear sight line distance to the south of 161st Ave = 1810 feet
Clear sight line distance to the north of 161st Ave =330 ft
Required stopping distance at 50 mph = 424 feet
Required stopping distance at 65 mph = 644 feet
Pedestrians crossing Variolite St in 91 hour time span -8
Accident Reports = 1  2/20/2012 car slid off the road due to slippery conditions
This crossing location has several factors that make it not suitable for a pedestrian crosswalk at this time.  The first and the most significant negative feature would be the lack of sight line distance to the north.  The sight line distance to the north is approximately 330 feet. A motorist traveling at 50 mph requires 424 feet to react to a pedestrian in the crosswalk and to begin braking to avoid a collision.  The next negative factor would be the speed on Variolite.  Through our data collection we found that the actual speed driven by 85% of the motorists on Variolite is 64.9 mph.  At that speed the the braking distance required would increase to 644 feet.  That's almost twice the the sight line distance available  to the north. The last point would be pedestrian volume at the intersection.  MnDot recommends as a minimum 20 people/ hour or 15 people /hour with an elderly or school facility near by to be considered for a  marked crosswalk. Staff installed a trail camera to capture pedestrian volumes at the intersection for our calculations.  The camera was installed the afternoon of May 4th and picked up the morning of May 8th. During that time period staff counted 8 people crossing Variolite St at 161st Ave. The City of Boulder CO has done extensive engineering studies in the area of crosswalk applications and their recommendation is  not to install a marked crosswalk at this type of location, as it is configured today.  In their studies the Variolite St/ 161st Ave intersection would be rated an E with the following recommendation for treatment "Do not install marked crosswalk at uncontrolled crossing. Determine if the speed limit can be effectively reduced to 40 mph AND a raised refuge median can be installed. If so, utilize Scenario D criteria above. If this is not possible, or if pedestrian volume falls above the RRFB limit line on Figure 2, consider HAWK beacon, pedestrian traffic signal, or grade-separated crossing.Specific Guidance : Consider HAWK beacon, pedestrian traffic signal or grade-separated crossing; application of these treatments will consider corridor signal progression, existing grades, physical constraints, and other engineering factors.  Scenario D reads: Install marked crosswalk with enhanced signs, pedestrian activated RRFBs, and geometric improvements to increase pedestrian visibility and reduce exposure Specific Guidance : Install raised median refuge island (unless it is a one-way street or one already exists) to shorten the pedestrian crossing distance and increase pedestrian visibility to motorists. [If a median refuge can not be constructed on a two-way street, Go To Scenario F]. Install marked crosswalk with "State Law - Yield to Pedestrian" signs WITH pedestrian activated RRFBs mounted on the side of the roadway and on median mounted signs; use standard (W11-2) advance pedestrian warning signs; use S1-1 signs for School Crossing locations. Consider adding neckdowns at the crossing if on-street parking exists on the roadway and storm drain considerations will allow. [Note: If pedestrian volume falls above the RRFB limit line on Figure 2, consider Hawk beacon, pedestrian traffic signal, or grade-separated crossing.] After reviewing the data and comparing it to the recommendations of MnDot and the City of Boulder CO staff recommends that a crosswalk NOT be installed at Variolite St and 161st Ave. Staff also recommends that this area be studied again in 2021 when Variolite street is scheduled for reconstruction.  At that time engineering could provide information on the possibility of lowering the grade of Variolite St some what to improve the sight line to the north.  Engineering could also provide for the feasibility and cost estimate of a raised refuge median for pedestrians at this location.

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General fund

Staff recommendation is to not install a crosswalk at this location at this time and to restudy this location for possible roadway improvements when Variolite St is scheduled for reconstruction in 2021.

Accept staff recommendation or reject the staff recommendation, and accept alternate recommendation based on committee discussion.