Re: [CTPP] ACS Data on Commuting

Andy: I'll respond to CTPP-News since this is a good question and a tough answer. Yes, you can derive Group Quarters workers by Means of transportation by subtracting TOTAL workers by means, say, taking CTPP Table 1-20 (workers by means of transportation (11) by length of US residence) LESS CTPP Table 1-35 (workers in HHs by means of transportation to work (11) by vehicles available in HH). This should work, UNLESS you need detailed transit-sub-modes, or bike vs walk splits. No, you can't get average travel time, or GQ workers by travel time distribution (or even HH workers by travel time distribution) from the CTPP. The only method I'm aware of to obtain AVERAGE TRAVEL TIME for HOUSEHOLD WORKERS is from Census 2000 PUMS. Of course, with PUMS, you can estimate the average travel time, and the travel time distributions, for GQ workers as well as household workers. For our region, there is no difference in the average travel time for total workers compared to household workers, so for Average Travel Time it may not be worth the effort to do the calculation in PUMS. It's probably region-specific: how different are your GQ workers compared to HH workers? We would be in big trouble with our non-motorized lobby if we didn't separately report bicycle from walk commuters. So, what I did was use the bike/walk split for TOTAL commuters (say, CTPP Table 1-2, by 18 means of transportaiton), and applied the bike/walk split to the Household Workers shown in CTPP Table 1-35. Or, you could always use PUMS, but it's easier just to use the bike/walk split from CTPP Table 1-2. One thing you may want to try is to "age" the Census 2000 GQ data up to 2005, using the GQ population estimates that are available, at a county-level, from the FSCPE web site. It's an educated WAG, but it might be useful when you want to make comparisons to independent data, like the employed resident data from the BLS' LAUS estimates. Chuck ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ ************************************************************** Very helpful post. Had a question for you. Do you know if there is a way to find out the number of group quarters workers, and their travel time and mode from 2000 Census? Just trying to get an idea of who we are missing in the 2005 ACS. Thanks for any assistance. Andy Pickard, P.E. Senior Transportation Engineer Hampton Roads Planning District Commission 723 Woodlake Drive Chesapeake, VA. 23320 Phone: 757.420.8300 Fax: 757.523.4881 apickard(a)hrpdc.org www.hrpdc.org