[CTPP] CTPP

At Ed Christopher's suggestion I am posting this to the list server. The following are some observations on the E-mail traffic I have been observing with respect to the CTPP summarization issues that I have raised with Ed at and since his sub-committee meeting at TRB last January. I must note that more recent e-mail is now starting to mention non-TAZ needs Phil Salopek in a recent e-mail says if you want Census geography instead of TAZ you don't have to participate in the TAZ up program....well at NYSDOT we want the statewide element of the CTPP to be detailed to CDP or lower and all the urban area elements for our use to be detailed to Census geography....tract and block group as the lowest level in the urban area. NYSDOT is interested in Census geography at the block group level especially in urban areas. Since each of the MPOs will be responding separately to the CTPP TAZ questionnaire, in addition to NYSDOT, then MPOs will indicate their need for TAZs or census geography. This way the MPOs can get what they want and the state can get what it needs. The glitch is if Census or Phil Salopek says the state has to have it the MPO way. Frankly I don't see the problem....the CTPP is part of the STF3. As part of STF3 it is summarized for CTPP parts A and 1 to the block / block group level and everything above from the get go. All that is required is the production of STF3 for the work place. County work flow is produced very early on in Census processing prior to the CTPP. These data are historically available on the REIS CD. So for the most part Census provides CTPP part C or 3 at the county level outside of CTPP. Clearly they have the routines in place to do it by specifying lower geography with selected focus (such as state or metro area). So its not just a CTPP processing software issue. The real issue is getting Census to recognize several things: 1 Census geography should always be available as a summarization level for all locations 2 If you are not an urbanized area 50,000+ then you likely do not have an MPO, and you do not have TAZs even though you may be a small urban area 3 TAZs are unique to "MPOs with models" and they don't define TAZs them the same way 4 If you are not now an urban area now and eventually become one in say 2002 then you are out of luck if TAZ is the only summarization level. This may be especially painful when we move to the ACS. 5 If you need to add TAZs , combine or subdivide them later you can't 6 This is not just an MPO product 7 This is really a summarization level issue like congressional boundaries 8 The problem that Census really needs to address is how to aggregate data up from lower geography for values such as mean and median; where summarization is really not possible ( median income or median travel time for example). Resolving this problem then enables Census or the end user to create the data at the lowest possible geographic unit and provide a summary level routine for computational values. All the MPOs need then is a simple lookup table to relate TAZs to Census geography and a routine to fix the computational values 9 From a purely economic product perspective Census geography means you can sell the product to third parties and recover the cost. TAZ is a summarization level unique to MPOs. There are lots of value added resellers of STF3 data now in addition to Census. The CTPP creates the workplace version of STF3 for a number of measures that are important to not only transportation planners but also to anyone interested in who, how and/or what arrives at work place locations. 10 Remember to make sure that the CTPP coding uses Census FIPS codes and not Census Place codes that Caliper used in 1990, otherwise it will not directly match common tiger based coverages. 11 The CTPP software that extracts the data table components from the CD rom needs to be improved on the data extraction part. Often one wants some range of Fips or town county, state codes for either the residence , work place or JTW and for selected fields (e.g. total trips, transit). As the 1990 CTPP software works you get all geography that you can point to on the map, not bad on the statewide side except if you want trips from selected origins outside the state. If you are using the urban element then selection is much more difficult because of the level of detail. In either case JTW from selected to selected geography is not easily do-able except in a database product. Some accommodation on the direct data selection side rather than through the visual graphical user interface would be helpful. Something like "extract" the Census routine for use with the Census STF CDs would be helpful. Otherwise you really need a database product like SAS, Paradox, dBASE or Access to get at the data the way you want. 12 What would really help would be Census creating STF3 for the workplace and the present county work flow data for lower summarization levels 13 Lastly it might be useful to note that at NYSDOT many of the information requests I receive come from the economic development interests. These requests reflect transportation or government concerns for attracting businesses into NYS. They come from within our agency or from our State Economic Development agency. These questions typically ask about workers first and then where they live. NYS can't be that different from the rest of the states that compete for the location of new jobs. Many of these requests are for areas just outside of the urban boundary. The fact that these type of informational questions are being asked illustrates the value of detailed Census geography and summarization levels beyond what has been provided for at the metropolitan planning through TAZs. As always I am available to discuss some of the more mechanical technical aspects of using the CTPP data in non TAZ analyses with anyone who wants to discuss why one size does not fit all.