[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 Data Center. 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. Caveats: 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 http://teachamerica.com/APP09/ (go to the Sunday session and look for DATA), and also at the LEHD OnTheMap home page http://lehd.did.census.gov/led/ . Elaine Murakami FHWA Office of Planning (Wash DC) 206-220-4460 (in Seattle)