Ed, Since I am not on the CTPP maillist, your message was forwarded to me by Bill Upton. Hence, I do not think that this response will be broadcast to the ctpp maillist. If you are so inclined, you are welcome to post it to the maillist. The Oregon Department of Transportation is currently building a second-generation statewide model integrating land use, transportation, and the economy. Descriptions of our modeling efforts can be found at http://www.odot.state.or.us/tdb/planning/modeling/modeling.html. As far as the construction of our statewide TAZs was concerned, we basically use aggregations of census tracts. In the MPO areas, this works out well because they have created TAZ districts that respect census geography. We did not create any statewide TAZs that were larger than a county, and in only two cases did we create TAZs that cross county lines (due to the effects of physical features). As long as CTPP continues to report transportation-related responses at the census tract level, we are relatively happy. In a fairly rural state like Oregon with its strict urban growth limits, many trips that might be considered of an intra-urban distance are actually inter-urban, and thus the CTPP data are quite useful for comparison against our modeling efforts. Your suggestion, "... that in non urban areas they should be counties. In urban areas they would, of course, represent the TAZs developed by the MPOs...", might be difficult to operationalize for MPOs that do not use census geography as a basis for their TAZs. And some non-urban areas that are experiencing rapid growth may find data reported only at the county level to be too gross for their planning objectives. Ed Arabas Associate Transportation Planner Transportation Planning Analysis Unit Oregon Department of Transportation 555 13th Street NE, Suite 2 Salem, OR 97301-4178 * Ph: 503-986-4398 * Fax: 503-986-4174 * Email: edward.p.arabas(a)state.or.us > -----Original Message----- > From: Ed Christopher [SMTP:berwyned@mcs.com] > Sent: Thursday, April 29, 1999 11:08 AM > To: ctpp maillist > Subject: [CTPP] statewide TAZs > > This post has two purposes. First to welcome 20 folks to the list serve > from states where we have ctpp contacts who have email addresses. There > are about 20 states we still need to track down. To the new folks let > me formally say" welcome to the CTPP listserve". We created this > listserve as a mechanism to keep the flow of information relative to the > CTPP moving. If you ever want to get off the listserve or change your > address the best thing is to drop me an email. You can also do this > through an automatic procedure which I will not bore you with now. > > The second and CTPP related reason for this post is to inquire about > statewide TAZs. Although the voice of one or two is not a > representative sample, the folks working on the CTPP are discussing the > issue of statewide TAZs and their construction, and could use some > input. One of the central questions that keeps coming up is, do we need > statewide TAZs? and, will they be useful for states? > > one could argue that the CTPP is journey to work data and it represents > short trips, mostly intraurban travel, when one considers statewide > travel in some of the larger (spatially big) states. On the other hand, > there are smaller states where the opposite is true. The bottom line of > all this would be the type of planning underway and the zonal structure > behind it. Ultimately it may take a state-to-state poll to identify who > needs what. But for now we could use some thoughts on this. Anyone > care to comment on the issue of statewide TAZs and more importantly what > they should be? > > To get things moving let me suggest that in non urban areas they should > be counties. in urban areas they would, of course, represent the TAZs > developed by the MPOs. > > (although i welcome your replies, i would hope that we keep this > discussion on the listserve by making sure you reply to listserve > address) > > thanks > ed christopher