I noticed that I used the word "workers" when talking about LEHD
OnTheMap, and it would be more precise to use the word "job".
[mailto:email@example.com] On Behalf Of
Sent: Thursday, August 27, 2009 4:25 PM
Subject: [CTPP] Documentation on using LEHD OnTheMap files
We (the royal "we") are interested in personal travel patterns, for a
variety of transportation planning applications. The CTPP program will
provide home-to-work origin-destination tables using multiple years of
surveys from the American Community Survey. But, other data sources
should be examined for their potential to augment the CTPP, for small
area origin-destination matrices. For example, many of you are aware of
my interest in using multi-day GPS. Each data source, including ACS
and the CTPP, has its own benefits and limitations. One of the datasets
of interest is the LEHD OntheMap "home-to-work" flows.
We would like to encourage more analysis and evaluation of the LEHD
OnTheMap data. While the LEHD OnTheMap interface is a user-friendly
web-based software http://lehd.did.census.gov/led/
, we believe that
transportation planners will be more interested in the potential of the
synthetic block data records (10 implicates are created in the data
synthesis process) to examine the origin/destination flow results.
These data are available for download on the Cornell University Virtual
I asked Laura McWethy at Cambridge Systematics to prepare some
documentation on the files, to make it easier for others to examine this
data. It is attached.
The files are large since they represent block-to-block pairs.
The data are synthetic. This is the first synthetic data product
approved by the Census Bureau's Disclosure Review Board. Data synthesis
is used to protect individual confidentiality.
The universe of workers (workers covered by unemployment insurance)
differs from "all workers"
You should take the time to understand the data sources and synthetic
data processes used to generate these results.
We are interested in your tests of the LEHD OnTheMap block level data.
I hope that Nathan Erlbaum and Aaron Westcott of New York State DOT will
share the results of their work on county-to-county flows.
Introductory material on LEHD OnTheMap is available through a recorded
presentation from the TRB Planning Applications conference in Houston
(go to the Sunday session and look for
DATA), and also at the LEHD OnTheMap home page
FHWA Office of Planning (Wash DC)
206-220-4460 (in Seattle)