Questionable Data

The ONEN Board cites data from a Colorado College analysis to assure us that lane reduction will not cause traffic congestion.  They specifically point out that, on average, Wahsatch, Weber, Cascade, and Nevada see between 2,200 and 2,500 vehicles per lane per day.  They compare this to 7,200 to 9,200 on Academy Boulevard and conclude that ONEN streets can easily handle a higher per lane average without getting congested.  But this analysis is off-base.

The per lane average for the roads near CC is poorly calculated. According to the same CC analysis, the daily vehicle totals for Wahsatch, Weber, Cascade, and Nevada are highly variable, from as low as 3,000 vehicles per day (vpd) on Weber to as high as 16,000 on Nevada.  Calculating per-lane averages across all four of these roads creates artificially low values for Cascade and Nevada.  In addition, a more recent count by City traffic engineers put Nevada at 18,000 vpd, not 16,000.

Academy Boulevard is not a valid comparison for ONEN streets. Academy is designed to handle much higher traffic levels without congestion.  It only has crosswalks at well-spaced, signaled intersections, whereas there are many unsignaled crosswalks in much closer proximity to each other in the ONEN and Patty Jewett neighborhoods. These cause more frequent and less predictable disruption to traffic.  The ONEN roads also pass many residential driveways, where traffic has to slow for exiting and entering vehicles.  And Academy Boulevard has turn lanes in addition to its four traffic lanes, allowing vehicles to turn without impeding through traffic.

It should be no surprise that Academy Boulevard (top) handles more traffic than ONEN roads (bottom).

It should be no surprise that Academy Boulevard (top) handles more traffic than ONEN roads (bottom).

The data doesn’t apply year-round. The data for the CC analysis was collected during September and doesn’t factor the detrimental effect of many months of winter weather on traffic.  Similarly there is no indication Academy Boulevard handles 9,200 vehicles per lane per day without congestion in rain, ice, or snow, or how the weather and plowing schedules vary between Academy and ONEN streets. 

The analysis considers heavy traffic “acceptable.” CC analyzed “level of service” during peak traffic periods for the roads in question and gave most a “B” grade, some a “C” or “D,” and none an “A.”  The report defined good levels of service to be when vehicles averaged 50-80% of the “free flow” speed, which was approximately 5-7 mph over the speed limit.  So for a 35 mph street (on which the free flow speed is 40-42mph) vehicles could average as low as 20mph and CC analysts would define that as good service.  For reference, 20 mph is the school zone speed restriction on Nevada for the morning and afternoon migration of Steele elementary children. This is the speed the ONEN plan considers acceptable for all hours of the day.

Proponents maintain that although traffic may feel ‘heavy’ at the Uintah intersections with Cascade and Nevada, it is acceptable.  But is “acceptable” preferable?  And if these roads warrant only “acceptable” grades under current traffic conditions, what grades will they get when road dieting increases the total vehicles per lane?

Finally, CC points to data showing traffic has decreased on ONEN streets over the last decade or so, primarily due to improvement on I-25.  But this improvement is a temporary effect.  The population of Colorado Springs has been increasing steadily for decades.  Any safety measure that primarily relies on lane reduction will have to be repeatedly revisited as traffic increases with population growth.

Larger studies conclude road dieting leads to congestion and doesn’t reduce accident rates. According to a report by the Federal Highway Administration (FHA), even with a dedicated center turn lane, road dieting is actually counterproductive on streets with 20,000 or more vpd.  And given the ONEN proposal does not include continuous center turn lanes, it seems highly likely the busiest routes (Nevada, Cascade) will see significant increases in congestion and thus accidents.  Indeed, Nevada currently handles 18,000 vpd and Uintah 30,000, which means they are already flirting with or are well over the limit for effective road dieting.  Population growth will only make matters worse.  As City Transportation Manager Kathleen Krager has stated, congestion and traffic volumes result in higher accident rates, and needless stops waste gas.

Even if road dieting didn’t increase congestion, it’s not effective at reducing accident rates.  The FHA report found that road diet sites had the same accident rates with the same severity as they had before lane reduction. And while the CC analysis was based on about a month of data from a few roads of questionable comparability, none of which had actually undergone road dieting, the FHA report is based on years of data from multiple road diet sites across multiple cities.  Additionally the FHA report was commissioned for general information, and not in an effort to get a specific policy implemented.  It’s reasonable to expect the FHA report to be the more relevant and accurate of the two.