Willow Glen Road Diet Report Analysis

Willow Glen, San Jose, California sign 19 June 2016

This is part of my continuing series on Willow Glen‘s Lincoln Avenue Roadway Configuration Pilot Project (“Road Diet“). These are observations from a detailed review of the San Jose Department of Transportation (“SJ-DOT”) publications on the Road Diet, looking at reports from the SJ-DOT from 2015 and 2016. Thanks to John Plocher  who assisted me with this review.

Please send comments, error corrections, or additions – they are welcome!  The San Jose City Council will discuss making the Road Diet (“Lincoln Avenue Pilot Project”) permanent at their 28 June 2016 meeting. Please join me there if you want your voice to be heard on this contentious local issue.
San Jose Department of Transportation, Road Diet Project Area Location Map, 6 June 2016
SJ-DOT Road Diet Project Area Location Map, 6 June 2016

San Jose Department of Transportation, Road Diet Volume and Speed Data Collection Location Map - Detail, 6 June 2016
SJ-DOT Road Diet Volume and Speed Data Collection Location Map – Detail, 6 June 2016

Analysis of the Road Diet 2016 Report from the SJ-DOT

Observations are listed roughly in the order that the information appears in the report.

  1. The Road Diet map of the SJ-DOT above shows the Project Area under consideration.
  2. A key finding from the 2016 SJ-DOT report is on p.4: “Based on the one year of ‘after’ collision data, it is inconclusive whether the modified lane configuration has had a measurable long-term impact on traffic safety… the total number of crashes was higher than the year prior to the pilot project.” That is, there were 22 crashes during the last year, compared to 8 the year before.
  3. My observations are limited to data inside the Project Area and Transition Zones which together are 1.1 miles long (Lincoln Avenue from Nevada Avenue to Lonus Street).  The Project Area without the Transition Zones is just 0.7 miles (Lincoln Avenue from Minnesota Avenue to Coe Avenue).
  4. There were SJ-DOT sensors (or “automatic recorders”) in a variety of locations inside and outside of the Project Area during the time of measurement.  Only two of SJ-DOT sensors were actually in the Project Area or Transition Zones: one South of Meredith Avenue on Lincoln Avenue, and the other South of Glen Eyrie Avenue on Lincoln Avenue.
  5. The SJ-DOT reports are full of detailed and confusing information from outside of the Project Area (measured because the SJ-DOT is responsible for more than just the Road Diet).
  6. On p.6 under “1B Neighborhood Street Traffic Volume and Speed Findings”, the report says most streets were unchanged but two were worse (two passed the threshold into “adverse”).  On pp.6-7 under “1c. Major Street Traffic Volume and Speed Findings”, both Pine and Minnesota showed a strong increase in speeders. That is, areas outside of the Road Diet area are less safe because of the Road Diet.
  7. On p.7 of the 2016 report, Travel Times are given for “the Lincoln Avenue Corridor” which is 2.64 miles long.  By more than doubling the area measured (from 1.1 miles to 2.64 miles), significant variations in the Non-Road-Diet sections distort the data and conclusions.
  8. There are only two indications of cost in the SJ-DOT report, both in the “Policy Alternatives” section on p.14.  One says that not modifying a traffic signal will save $65,000 and the other says that removing modifications to that signal will cost $15,000.  There is no indication how much has been spent on the Road Diet so far, including the long list of additional improvements already implemented (listed on p.10).  There is also no indication of what it would cost to remove the Road Diet or make it permanent.
  9.  The San Jose City Budget Message dated 30 May 2014 includes the following: “Pedestrian Safety …The City Manager is directed to allocate $45,000 in one-time Construction Excise Tax funding for this type of minor pedestrian safety improvement on Lincoln Avenue.”  This is the only funding reference we have identified so far for the Road Diet.
  10. On p.17, “Calmer Traffic Environment” says that “motor vehicle speeds decreased on Lincoln Avenue”.  Looking at “Attachment B – Lincoln Avenue Volume & Speed Summary”, the average change in the Project Area was 7% decrease in volume, and the average percent of speeders in the Project Area went down 6.3%.
  11. The SJ-DOT data analysis does not define a margin of error, making it hard to understand if any of SJ-DOT’s reported measures are statistically significant.  Variations seen in SJ-DOT report tables for areas outside of the Road Diet are often much larger than variations inside of the Road Diet area.
    • Example of variation outside of the Project Area: “Attachment E – Lincoln Avenue Travel Time” shows a -30% to +82% change to areas outside of the Road Diet.
    • Example where margin of error matters: “Attachment B – Lincoln Avenue Volume & Speed Summary” show that volume and speed measures are down on average 4% in 2016.  This measure may very well be so small as to be within the statistical margin of error.
  12. “Attachment E – Lincoln Avenue Travel Time” shows for the Minnesota to Willow segment of Lincoln Avenue:
    • Northbound traffic was on average faster (22% less time or 35 seconds faster)
    • Southbound traffic was on average much slower (36% more time or 1 minute, 13 seconds slower)
  13. “Attachment F – Lincoln Avenue Intersection Level of Service Summary” shows that the LOS (Level of Service) is unchanged for the Lincoln/Minnesota and Lincoln/Willow intersections.  Both of these intersections are still “D” on a scale of A to F, where: A is less than ten seconds, and F is more than 80 seconds delay to get through an intersection.

Click here to see the entire Willow Glen Road Diet Series.

Willow Glen, San Jose, California sign 17 June 2016

Images Copyright 2016 by Katy Dickinson, with thanks to the SJ-DOT for their maps

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