More Bad Reports - Street Sweeping. Part 2

Dr. Jim Gardner
Dr. Jim Gardner

Last week we saw that the City’s theory of how to improve water quality through street sweeping was not supported by the empirical data. Today we’ll look at what the City did anyway.



The City claims to have received complaints from 4 areas involving 12 streets –

1. Ridge Route west of Rockfield, Gowdy, Red Robin Way, Golden Eagle

2. Anthony Drive, Debra Street, Donna Lane, and Tama Drive

3. Cherry Street north of Jeronimo to Ashbrook, 2nd Street

4. Cherry Street north of Trabuco to Darrin Drive



The City

1. Counted the number of vehicles parked

2. Visited the 12 streets and took data for 4 weeks, counting the number of cars parked to determine “whether the percentage of street blockage by vehicles meets, or exceeds 25% of the street, and potentially whether this has negatively affected water quality”

Of the 12 streets under study, only 5 achieved a level of 25% or more. In other words, on these 5 streets, the City determined that the average number of vehicles on the streets during street sweeping represented 25% or more of the parking capacity. The 5 streets were:

1. Cherry Street – 58.5%

2. Ridge Route – 53.1%

3. Gowdy Ave – 36.7%

4. 2nd Street – 34.6%

5. Anthony Drive – 30.5%

For various reasons, the staff recommended against Gowdy, Anthony, and 2nd Street, and narrowed the field to 2 – Cherry and Ridge Route.



In Part 2 of their study, the City

1.    Created “a temporary restriction with ‘no parking’ signs during the four-hour sweeping window”

2.    After a one week period, enforced the posted signs during the temporary restriction

For some reason the intervention was done on all 12 streets, rather than the 5 streets that exceeded the 25% criteria, or the 2 streets finally chosen. This makes no sense, and represents extra work that didn’t need to be done. Nor was any attempt made to analyze the differences (if any) between the 5 blocked streets and the 7 unblocked streets.

The City reported -

1.    “Over a period of 4 weeks…104 fewer vehicles parked along these streets when the temporary restrictions were in place and Police Services diligently enforced… This represents a 25% decrease in the total amount of vehicles…”

2.    “The City issued 79 violations and received 2 complaints in response to these notices.”

3.    “Generally staff received positive feedback from residents…”

On this basis, the City is recommending going ahead on the 2 targeted streets.

Now that you see the study, we can discuss some of the flaws, in addition to the main flaws already outlined – namely, both the hypothesis and the theory being tested have little if any basis in fact. Tomorrow we'll look more closely at the report.


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