New subject: FHWA's NHTS program manager position

3 Mar 2010

Thanks to all who responded.  I've summarized, paraphrased and quoted below possible
reasons below and added a few comments as appropriate:

1.      Other modes such as bicycling, motorcycles and motor scooters. (I think these are
covered by the data in 20068 ACS table B08141 so they are not likely the source of the
problem.)

2.      Leased, not owned, autos treated not counted as vehicles "kept for use by
members of this household" (This would be a misinterpretation of the ACS question but
stranger things have happened.  Other types of respondent errors could be in play here as
well.)

3.      Problem with data imputed by the Census Bureau for non-responders.

4.      Using a company car on loan, a zip car a neighbors car, a parent's car or
another car sharing service. (ZipCar is popular in Cambridge but I doubt that would cover
too many people.  Company cars might explain some but again seems an unlikely explanation
for almost 700 commutes out of 48,600. Garaging a car not registered in Cambridge is
difficult as we require a resident permit for on street parking and off street parking
spaces are few and expensive. Over 60% of the housing stock is rentals, often with no
dedicated parking space included in the rent.)

5.      Non-standard work week such as travel to a conference.  (This might be a not
insignificant source.  I've always been surprised by the number of local residents who
JTW data shows as "commuting to work" in California.)

6.      Based on the 2009 NHTS, the ACS result seems reasonable. In the 2009 NHTS
(weighted results), 12% of persons in zero-vehicle households who travelled to work
"last week", did so in a vehicle with one person in it.  This works out to be
500k people out of 4,260k.

7.      This phenomenon shows up in NHTS as well and appears to be a very real result of
the fact that some share of folks used borrowed cars for travel.  It may be a young adult
who doesn't own a car but has one available from dad, folks renting, folks borrowing
etc. In consumer expenditure surveys non-car owning households also have non trival auto
related expenses for  travel.  It is not uncommon for non-car households to travel more
PMT in SOV than on transit.  In consumer expenditure surveys non-car owning households
also have non trival auto related expenses for  travel.

Thanks to all for your help!

Cliff Cook
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Original post:

I'm hoping someone can help me address this question from a colleague.  He put
together a table from the 2006-2008 ACS showing mode of journey to work by vehicles owned
and came up with surprisingly large numbers who do not won a car yet drive alone to work.
No doubt, there are a few people who fit this category but my guess is that this largely
is the result of either people misunderstanding the question or some sort of coding
problem. Here is an excerpt from his email ( the Cambridge here is Cambridge,
Massachusetts):

I'm looking at ACS data and specifically at cities and percent workers have no car
available.  From that I'm then looking to see how those workers get to work.

The attached worksheet shows my work.  What is strange is that it shows for Cambridge that
6.6% of people without a car available drove alone to work.  The percent is similar to
Boston. And NYC has 3.4% of workers with No vehicles available driving alone to work.

So, the question is, how can someone without a vehicle drive to work alone?  Do you have
any ideas on this?  It could be someone doesn't own a vehicle, but drives a
friend's car to work. Or has no car of their own, but uses a company car to get to
work.  But seems like a high number for this.

Can anyone shed any light on this?
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Clifford Cook
 Planning Information Manager
  Cambridge Community Development Dept.
   344 Broadway
    Cambridge, MA. 02139
     617/349-4656  FAX 617/349-4669  TTY 617/349-4621
      email => ccook(a)cambridgema.gov
       web site => <http://www.cambridgema.gov/~CDD/>

No Car but Drives to Work Alone