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Finding a new way to measure cities’ bike friendliness in the United States

November 3, 2012 / / 8 Comments

A really smart person could come up with a way to measure day-to-day bike friendliness based on how well cities adhere to standards that keep roads clear of obstructions that further frustrate the commute, like construction projects that squeeze bikes and cars together. 

I work at home. There are some days when I only leave my house to get milk from the Mexican grocery store at the end of my block (which makes awesome burritos). That means I ride my bike half as much as people who commute to work. on their bikes. Today I had a bunch of errands to run: drop off stuff, buy stuff, take pictures of stuff for my blog, Grid Chicago.

It was a very frustrating experience. I don’t need to go into details about how I was harassed by people who the state so graciously awarded a license to drive. But it happened. And it happens a hundred times a day to people cycle commuting in Chicago. I got to thinking about “bike friendly” cities. Is there a way to incorporate driver attitudes in there? I tweeted:

[tweet_embed id=264575958374305792]

Later I had the idea to use some very simple but objective measurements to create a new bike friendliness metric. It would help ensure that “Silver” (a ranking the League of American Bicyclists [LAB] uses) in one city means the same as “Silver”. It can expand from here but basically it works like this:

  • The share of people going to work who go by bike is a proxy for how “friendly” a city is to biking.
  • If a city has a lot of people biking to work, it must be friendly.
  • If a city has a few people biking to work, it must be non-friendly.
  • Cities are compared to each other to determine friendly and non-friendly.
  • The metric uses standard deviation to score cities.

Stop me if this has already been done.

I created a spreadsheet that lists the top 10 populous cities in the United States. I then added 10 more cities: Austin, Boston, Davis, Madison, Minneapolis, Portland, San Francisco, Seattle, and Washington, D.C. In the next column I listed their bike commute share from the American Community Survey 2006-2010 5-year estimates. I calculated the standard deviation and mean of these shares and then in another column used Apple Numbers’s STANDARDIZE function:

The STANDARDIZE function returns a normalized value from a distribution characterized by a given mean and standard deviation.

I think that’s what I want. And the output is close to what I expected. I then found the LAB ranking for each city and found the variance of each ranking to see how far apart each city within one ranking was from another city in the same ranking. The results were interesting: the higher the ranking, the more variance there was.

Hurricane Sandy prompted a lot of New Yorkers to bike. It made headlines, even. Photo by Doug Gordon. 

I wanted to add another metric of bike friendliness, and that’s density. To me, a higher density of people would mean a higher density of places to go (shop, eat, learn, enjoy) and friends and family would be closer, too. Or the possibility of meeting new people nearby would be higher. Yeah, I’m making a lot of assumptions here. So I applied the STANDARDIZE function there as well. I added this number to the previous STANDARDIZE result and that became the city’s score.

So, in this new, weird ranking system, the most bicycle friendly cities are…drum roll please…

  1. Davis, California (Platinum)
  2. New York City (Silver) *
  3. San Francisco (Gold) *
  4. Boulder (Platinum)
  5. Boston (Silver)
  6. Philadelphia (Silver)
  7. Tie: Chicago*, Washington, D.C. (Silver)
  8. Tie: Portland* (Platinum), Minneapolis* (Gold)

Remember, I said above that any author of a list should spend at least a day cycling in each city. I’ve starred the cities where I’ve done that – I’ve cycled in 5 cities for at least a day.

I only calculated 20 cities. Ideally I’d calculate it for the top 50 most populous cities AND for every city that’s been ranked by LAB.

LAB cities list (PDF). My spreadsheet (XLS).

New Honda commercial tells people it’s okay to drive their car while sleepy

October 31, 2012 / / 10 Comments

Eff you, Honda.

Partial transcript:

We know you.

[Shows guy yawning.]

We know you have to rise early and work late.

[Shows someone drinking coffee. Shows “Lane Departure Warning” signal and an obscured person driving on a rural road driving their Honda Accord in the opposite direction lane, then swerving back into the correct lane.]

With not enough sleep in between.

[Shows hands of driver moving the steering wheel to maneuver the car back into the correct lane with driver’s shoulders moving dramatically to either show that the steering wheel had to be yanked or that he’s shrugging off the moment.]

The rest of the commercial shows different features and makes stupid comments about your needs and desires.

It’s not okay to drive in that condition.

Tell it, Sue Baker! Car crashes are not accidents

October 29, 2012 / / 0 Comments

“It was an accident!”, said the driver. Photo by Katherine Hodges. 

Because of Hurricane Sandy, the New York Times paywall is down so I’m reading every article I can, starting with “Safety Lessons from the Morgue“:

As she explains it, “To say that a car crash is an accident is to say it’s a matter of chance, a surprise, but car crashes happen all the time, and the injuries that people sustain in those crashes are usually predictable and preventable.”

Another car crash-related excerpt from the article about Sue Baker, injury prevention researcher extraordinaire:

In one of her recent projects, Baker looked at another aspect of highway deaths. The study, which Baker prepared with David Swedler, a doctoral candidate, examined more than 14,000 fatal crashes involving teenage drivers. They found that male drivers were almost twice as likely as female drivers to have had high levels of alcohol in their blood and were also more likely to have been speeding and driving recklessly. Significantly, 38 percent of 15-year-old drivers, both male and female, were found to have been speeding, but by age 19, female speeders dropped to 22 percent, while male speeders remained steady at 38 percent.

Those differences, Baker says, suggest that boys and girls should not automatically receive the same driver training — and that boys should perhaps receive their license at an older age than girls. “Males might scream foul,” Baker acknowledges, “but let them.”

Yes, let them. It’s too easy to get a driver’s license in this country.  I love her style:

In 1979, at a Department of Transportation public hearing about the dangers faced by truck drivers, Baker angrily explained, “Isn’t it time we did some crash testing with trucks and dummies, rather than with drivers themselves?” Later, according to Baker, the trucking industry hired a researcher to try to discredit her driver-safety studies. Unable to uncover problems with her work, he eventually gave up and called to tell her about his assignment. [emphasis added]

Not everything is perfect with injury prevention studies, though.

In the mid-1970s, [Sam] Peltzman did research on highway fatalities that suggested that mandatory safety features like seat belts and padded dashboards actually encouraged people to drive less cautiously.

Tom Vanderbilt talked about that in “Traffic“, which is basically my favorite transportation book, even mentioning Mr. Peltzman. Flip to page 181 to read it. Vanderbilt lists all of the different labels for that behavior:

  • the Peltzman effect
  • risk homeostasis
  • risk compensation
  • offset hypothesis

He summarizes: “What they are saying, to crudely lump all of them together, is that we change our behavior in response to perceived risk, without even being aware that we are doing so”. But Sue has a response:

Baker acknowledges that there may be some individuals in cars with anti-lock brakes, for example, who may not apply the brakes as soon as they did with the old brakes. But she insists there is no evidence that better brakes or air bags have encouraged recklessness — that they have in fact saved many thousands of lives. “What concerns me,” she says, “is that these spurious arguments are used by companies to bolster their opposition to beneficial safety regulation.

I think it’s safe to say now that she’s a personal hero of mine. But way, there’s just one more thing!

As she talked about what still needed to be done, her voice was tinged with anger: “Buildings need to be designed so it’s not so easy to fall down stairs. All new homes should have sprinklers. Traffic lights should be timed for pedestrians, not to move as many cars as possible through an intersection.

Yep. Exactly what we don’t do. We make ’em wait. And wait. Without even telling people the traffic signal’s even acknowledged their presence.

More

Links between pedestrian safety and crime

October 25, 2012 / / 4 Comments

Chicago Pedestrian Plan

Safety item 20: Analyze the relationship between pedestrian safety and crime (download the plan)

The 2011 Chicago Pedestrian Crash Analysis identified a strong correlation between community areas with high numbers of pedestrian crashes and community areas with high crime rates. Correlation does not indicate causation and further study is necessary to understand this relationship and the potential broader benefits of pedestrian safety improvements. [From page 62 in the 2012 Chicago Pedestrian Plan.]

ACTIONS

Short Term

  • Identify and obtain funding for this study.
  • Identify a location for safety improvements and obtain data for the “before” conditions.

Mid Term

  • Design and implement pedestrian safety improvements.
  • Develop a pedestrian safety enforcement plan for the area for the duration of the project.
  • Analyze the effects on pedestrian safety and crime.

MILESTONES

  1. Initiate this study by 2013 and complete by 2015.

ADDITIONAL RESOURCES

National Highway Traffic Safety Administration. Data-Driven Approaches to Crime and Traffic Safety (DDACTS). 2011. [I don’t fully see the connection, but this reference was linked to a page on NYC Department of Transportation’s website.]

Pedestrian Crash Analysis

The summary report didn’t contain the word “crime”. The technical report contained 2 mentions, with an additional chart. They are quoted in the ordered list below. Download the summary report.

  1. In an examination of various factors including crime, income, race, language spoken, and Walk Score®, the strongest correlation found was between pedestrian crashes and crime
  2. Finally, crime statistics were compared to pedestrian crashes to determine if a correlation could be identified, using data from the Chicago Police Department (CPD) annual reports for 2005 through 2009. The annual reports include incidences of crime by Chicago Community Area (CCA). The statistics for the years 2005 through 2009 were averaged and compared to the aver- age number of fatal and serious injury pedestrian crashes over the same time period in each CCA. Of these factors, crime was the only variable that correlated to pedestrian crashes. Figure 1 shows the correlation between crime and pedestrian crashes was very high. However, there may be many variables responsible for this correlation.
  3. Figure 1: Crime vs. Fatal and Serious Injury Pedestrian Crashes by Chicago Community Area

Figure 1.

I have a few criticisms of this analysis: it lacks raw data; the data tables included in the technical report are of limited length, listing only the “top” items of any metric; the summary report lists many silly factoids; the maps are low resolution and of a limited scale – their design could be modified to improve their usefulness in communicating the crash frequencies of the marked locations. The analysis is reliable.

The technical report includes the state’s guide on how police officers are trained to fill out a crash report form. It also includes relevant crash reporting laws in Illinois. Download the technical report.

Special post for S.M.