Re: [CTPP] CTPP

Nathan and the CTPP newsgroup: A few comments on Nathan's 12/9/98 posting. First, we hear what you are saying, Nathan, regarding your interest in NYSDOT in getting block group data, over and above what the MPOs receive. We are trying to see how we might accomodate this; we'll keep everyone posted through this newsgroup on the progress. Secondly, however, I have to point out that a number of the assumptions you have regarding the production of the CTPP and its relation to STF3 are just plain wrong. The CTPP is --NOT--repeat NOT-- part of STF3. The CTPP is programmed by a different group of people, at a different time, independently of anything done for STF3. The only thing they have in common is that they both use the same source file, our internal sample edited detail file. We formatted the CTPP to look like STF3 to make it easier for people who were accustomed to using Bureau summary tape files. But the whole idea behind the CTPP is that it is CUSTOM (read non-standard) content for CUSTOM geography. The content is tailored to transportation planning uses and consists of much more detailed cross-tabulations than the single variable distributions found on STF3. Even if the Bureau produced a workplace-based STF3 as you suggest (an idea which has been rejected in the past), my understanding is that the content would still be lacking for transportation planning uses. So while this is a legitimate issue for people interested in place of work data generally, it's not really a CTPP issue. On the other hand, although we make the CTPP content available for standard Census geographic units like tracts or block groups, most MPOs choose to have the data created for TAZs, a non-standard or custom geographic unit. So even if the content of STF3 was more detailed (which for 2000, it will not be) the geography wouldn't be as useful for transportation planners and there would still be a need for a CTPP. So it seems to me that there's really little point in talking about STF3 in relation to CTPP. They aren't related. Similarly, there is no standard census product that provides county-to-county work flows. The file produced in December of 1992 that Chuck mentioned (STF-S-5) was again a special tabulation done out of this office for a number of customers, one of which was BEA whom I believe produces the REIS CD you mentioned. (In other words, if we don't produce the special tab, there is no data for them to put on their CD.) This product lacks the means of transportation, travel time, and peak/off peak information provided in CTPP Parts 3 and C, which I assume transportation planners generally find to be valuable. This product was produced by the CTPP programmers (again having nothing to do with STF3) and would have been done considerably later, IF AT ALL, had it relied on non-CTPP staff. Yes, it probably delayed the first releases of CTPP by a few months, but as Chuck indicated, it was a product that was used by the transportation planning community as well as others like BEA, BLS, etc. For 2000, I assume that as in the past, there will not be a county commuter flow product created as a standard product. If sponsors are found for such a product, then the likelihood that it will be created is increased. My own opinion is that if such a tabulation is going to be produced, we should try to broaden its scope and include characteristics of the commuters between counties, not just counts. I think this would make the product more marketable to a larger audience. However, it would also likely increase the size and complexity of the dataset. We might also consider producing commuting flows for lower-level geography (say, places above a certain size), as part of such a product, but I haven't really seen the demand for this. I'd be inclined to say that what we do in the statewide CTPP for place-level flows is sufficient. You also mention that Census geographic units should always be available as a summary level. Well, this is your opinion and you're entitled to it, BUT, I think it's a rather narrow view. First, I think the evidence indicates that this is a minority view in the transportation planning community. In 1980 we produced something called Part V of the UTPP which was data by block group of work, even where the rest of the package was tabulated for TAZs. I know of very few people who used these data. In 1990 we did something similar, producing Part 7 of the CTPP in all urban packages which was data by tract of work. Use of Part 7 has been isolated at best. So it is clear to me that TAZs are of primary importance and there is little demand for standard census geography summaries as you suggest. I have comments on some of the other points you made, but this is too long already, so I'll end here. But I encourage you and others to continue to voice your sentiments and concerns. We may not always agree, nor be able to implement your suggestions, but we will listen and try to make improvements. --Phil