How many trips are two miles or less?

Bike advocates frequently repeat a claim that 40% of all trips are two miles or less.

Where does that 40% figure come from. A “Nationwide Personal Transportation Survey” is often cited, but it’s one of those statistics that’s endlessly repeated a bit like that bogus 85% figure frequently mentioned for bicycle helmets. Lisa Halverstadt of Voice of San Diego — a nonprofit investigative news organization — looked into the stats after San Diego’s city council president Todd Gloria repeated the 40% figure during a bike event.

Her shocking discovery — it’s true! Well, sort of. 40% of all trips reported by this national survey in 2009 showed 40% of all trips — whether by car, bus, walking or biking — are indeed two miles or less.

But then Halverstadt dinged Gloria’s statement as “misleading” because when you narrow the mode down to cars only, 69% of trips are two miles or less.

In other words, the ratio of short trips actually goes up, according to Halverstadt. Watch her video report for Voice of San Diego below, or read the text from the Voice website, where you can also see numbers for San Diego residents (37% of all trips, 32% of car trips). And if you know how to tease the data from the database, you can grab it straight from the horse’s mouth at the National Household Travel Survey.



18 Comments

  • March 26, 2013 - 10:23 am | Permalink

    Interesting….thanks.

  • Steve Piercy
    March 26, 2013 - 12:55 pm | Permalink

    I just fact-checked the writer’s fact checking, and I cannot figure out how she got her numbers. Here’s what I did. Visit:

    http://nhts.ornl.gov/det/Extraction3.aspx

    I did two searches, both of which had these values selected:
    Year = 2009
    Household Income = Combine Total
    Age = Combine Total
    Gender = Combine Total
    Worker = Combine Total
    Mode = Combine Total
    Purpose = Combine Total

    And the first search:
    Miles = Combine Total

    Person Trips (in millions) = 392,022.84

    And the second search:
    Miles = Under 1 mile AND 1-2 miles
    Person Trips (in millions) = 31,269.25 + 35,846.1
    = 67,115.35

    Thus the percentage of all trips that are 2 miles or less is:

    67,115.35 / 392,022.84 = 28.06%

    Further isolating to just Mode = POV, and repeating the searches:

    And the first:
    Miles = Combine Total

    Person Trips (in millions) = 327,117.65

    And the second:
    Miles = Under 1 mile AND 1-2 miles
    Person Trips (in millions) = 31,269.25 + 35,846.1
    = 67,115.35

    Thus the percentage of all trips that are 2 miles or less is:

    67,115.35/327,117.65 = 20.52%

    Which is lower than the 69.1% in the article.

  • March 26, 2013 - 4:34 pm | Permalink

    I participated in the survey last year, and my travels were all by bike or foot, and way under 2 miles. Not that it matters to the statistics, just thought I’d share. That’s me, ridiculous homebody!

  • Dylan
    March 26, 2013 - 6:23 pm | Permalink
  • Dylan
    March 26, 2013 - 6:33 pm | Permalink

    League of American Bicyclists sez: “Our thanks to the FHWA Office of Policy for help accessing these data.”

  • Steve Piercy
    March 26, 2013 - 6:53 pm | Permalink

    Neither these articles nor LAB provide their methodology for determining percentages, so their assumptions, calculations, and conclusions cannot be verified. That does not mean they are wrong. I merely don’t take anyone’s word—even if it sounds great—if I cannot fact check it.

    If I made an error, then please point out where I went wrong and how to correct it. I will retract my results if they are in error.

    If the article is in error, then let’s get the methodology right so we cyclists don’t come off like spin artists.

  • March 27, 2013 - 12:15 pm | Permalink

    The picture is broadly similar in the UK – see page 7 of this report from Sustrans (the country’s leading sustainable transport charity*), which shows 43% of all trips are less than 3km (~2 miles).

    *Declaration of interest: I work for Sustrans, and the lovely people in their Research & Monitoring Department are in the office next door!

  • March 27, 2013 - 12:16 pm | Permalink
  • March 27, 2013 - 10:32 pm | Permalink

    I contacted Mr. Doug Hecox from the DOT. Mr. Hecox pointed out that I was using the wrong tool, and directed me to the correct one. Here’s what I did.

    Start here.
    http://nhts.ornl.gov/tables09/ae/TableDesigner.aspx

    Enter these values.

    Statistics

    Survey = 2009 NHTS

    Analysis Variable = Annual person trips (Travel Day PT)

    Type of Table = One Way

    Statistics = [X] Sample size

    [X] Sum

    [X] Percent

    [ ] Margin of error (warning: takes a long time)

    [X] Exclude missing (e.g., appropriate skip)

    Categorize Results By

    Row Variable = Calculated Trip distance converted into miles (TRPMILES)

    [X] Use my variable categories

    0 – .99 = ‘ 2 miles’

    Options

    Title = (blank)

    Subgroup = (blank)

    Results: http://nhts.ornl.gov/tables09/ae/work/Job27794.html

    Which is exactly the same results as reported.

    Then I went crazy with the data. That is a *really* nifty tool. :)

    @Karl McCracken thanks for the link to the UK study.

  • March 27, 2013 - 10:34 pm | Permalink

    Bah, stoopid word press munged my variable categories. >:(

    Anyway, the categories I entered were:

    0 – .99 = 2 miles

    with single quote marks around the right-hand side value.

  • March 27, 2013 - 10:35 pm | Permalink

    ARGH!

    0 – .99 = less than 1 mile
    1.00 – 2.00 = 1 – 2 miles
    2.01 – 9999 = greater than 2 miles

  • Pingback: Are you logging your bike trips? | Tucson VeloTucson Velo

  • Pingback: Weekly Reading: How Good Is Biking and Walking for Your Health? « SvR Design

  • Bikee
    August 18, 2013 - 1:10 pm | Permalink

    Hi Steve Piercy,

    I tried doing what you did on http://nhts.ornl.gov/tables09/ae/TableDesigner.aspx

    But for Row Variable, I can’t select TRPMILES. The options I have available in alphabetic order go: “…TDAYDATE, TRAVDAY, URBAN…”

    I’ve also tried using the search tool for TRPMILES, and it’s not returning it as a valid variable. Any suggestions on what I am doing wrong?

    Thanks.

  • August 18, 2013 - 2:49 pm | Permalink

    @bikee

    See these screenshots.

    http://imgur.com/PlJie1B,tM43xR2#1

    http://imgur.com/PlJie1B,tM43xR2#2

    WordPress strips out the singe quote marks around the right-hand side, as previously stated here:

    http://www.cyclelicio.us/2013/40-percent-under-two-miles/#comment-40820

  • August 19, 2013 - 9:14 am | Permalink

    Steve, thanks – I was able to get the stats you grabbed.

  • Pingback: 9 Things Drivers Need to Stop Saying in the Bikes vs. Cars Debate – Wired | Car Tools Shop

  • Pingback: 9 Things Drivers Need to Stop Saying in the Bikes vs. Cars Debate – Wired | Car Washology

  • Leave a Reply