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?
Thanks
Cliff Cook
-----------------------------------------------------------------------------
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/>
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 (500k people out of 4,260k).
Rob Case
>>> ccook(a)cambridgema.gov 3/2/2010 3:52 PM >>>
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?
Thanks
Cliff Cook
-----------------------------------------------------------------------------
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/>
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Thanks Liang for sharing the slides, much appreciated,very interesting
presentation on a proposed metholodology for using larger area ACS
estimates (themselves with a fairly large margin of error, as we know)
to synthesize to PUMAs, which are themselves large area geography.
However no margins of error are addressed that I can see in the
presentation, though the last slide has as "next steps" an item that
proposes inquiry into census block groups and census tracts. One
potential issue is where do the controls for the small-area data come
from if we are somehow coming up with the controls themselves, and then
synthesizing cross-tabs from those controls.
Among other things, margins of errors are something to keep in mind for
NCHRP 08-79.
Thanks,
Guy
Guy Rousseau
Modeling Manager
Atlanta Regional Commission
From: ctpp-news-bounces(a)chrispy.net
[mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of Liang Long
Sent: Thursday, February 25, 2010 10:50 AM
To: ctpp-news(a)chrispy.net
Subject: [CTPP] Sakshaug's slides on CS FTP server
As many of you are requiring Joe's research materials, I asked Joe's
approval for sharing his presentation slides. Here it is:
ftp://ftp.camsys.com/temp/outgoing/CTPP/JoeSakshaug_Synthetic.pdf
<ftp://ftp.camsys.com/temp/outgoing/CTPP/JoeSakshaug_Synthetic.pdf>
Liang Long
Cambridge Systematics, Inc.
4800 Hampden Lane
Suite 800
Bethesda, MD 20814
tel 301 347 9141
fax 301 347 0101
FHWA 202-366-6971
e-mail llong(a)camsys.comwww.camsys.com
