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Today's Topics:

  1. CTPP Flows and Traffic Assignments (Cervenka, Kenneth (FTA))
  2. Re: CTPP Flows and Traffic Assignments (Don Cooper)


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Message: 1
Date: Fri, 12 Aug 2016 12:09:18 +0000
From: "Cervenka, Kenneth (FTA)" <Kenneth.Cervenka@dot.gov>
Subject: [CTPP] CTPP Flows and Traffic Assignments
To: "ctpp-news@chrispy.net" <ctpp-news@chrispy.net>
Message-ID:
    <BY2PR09MB06755A9DDB4002F1586ECCD08F1F0@BY2PR09MB0675.namprd09.prod.outlook.com>
   
Content-Type: text/plain; charset="us-ascii"

Hello,
I sent the following to the TMIP (Travel Model Improvement Program) listserv earlier this morning, but since this is focused on CTPP, I would be happy to get comments from the CTPP group as well.

It is somewhat common practice to compare district-to-district flows consisting of aggregations of TAZ-to-TAZ travel model outputs for Home-to-Work person trips to similar home-to-work aggregations based on CTPP flows.  Since most AM peak period auto travel consists of home-to-work movements, what successes or failures have forecasters had in the use of TAZ-to-TAZ CTPP data in an AM peak period UE traffic assignment?  Or some variation that might include enhancements to the commuter flow data to represent the (relatively small)  non-commuter AM Peak vehicle travel and/or other adjustments to the CTPP's representation of home-to-work travel?  I am aware of one test that notes the "lumpiness" of working directly with the TAZ-to-TAZ level CTPP data (with the end result being the %RMSE statistics do not look stellar), but am also aware of many forecasters who manage to squeeze good value out of whatever ground truth-based data is available.  I am reluctant to bring up the "origi!
n-destination matrix estimation" approach that can start with even a seed matrix of 1's in every TAZ to TAZ cell, but would be happy to hear of any CTPP-based efforts where the study has summarized how the "raw" CTPP trip table matrix compares to the final adjusted "seems to assign well" matrix.
I am not expecting to see many responses that focus on use of CTPP in this type of exercise, and suggest that you reply directly to this listerv rather than just to me, since whatever info you might offer might inspire others to comment.  But if there is some reason why that may be a problem, I am happy to get your comments directly to the email noted below (and can send to the full listserv without attribution to you).
Thanks in advance,
Ken Cervenka
Ken.Cervenka@dot.gov<mailto:Ken.Cervenka@dot.gov>


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Message: 2
Date: Fri, 12 Aug 2016 11:02:42 -0400
From: Don Cooper <donc@bactsmpo.org>
Subject: Re: [CTPP] CTPP Flows and Traffic Assignments
To: ctpp-news@chrispy.net
Message-ID: <7ab516405a9f7170691b40a63b919f80@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

AM peak trips are not predominantly home to work. NHTS shows that non work
trips comprise over 50% of am peak trips. Suggestion:  Talk to Nancy
McGuckin.



*From:* ctpp-news-bounces@chrispy.net [mailto:ctpp-news-bounces@chrispy.net]
*On Behalf Of *Cervenka, Kenneth (FTA)
*Sent:* Friday, August 12, 2016 8:09 AM
*To:* ctpp-news@chrispy.net
*Subject:* [CTPP] CTPP Flows and Traffic Assignments



Hello,

I sent the following to the TMIP (Travel Model Improvement Program)
listserv earlier this morning, but since this is focused on CTPP, I would
be happy to get comments from the CTPP group as well.



It is somewhat common practice to compare district-to-district flows
consisting of aggregations of TAZ-to-TAZ travel model outputs for
Home-to-Work person trips to similar home-to-work aggregations based on
CTPP flows.  Since most AM peak period auto travel consists of home-to-work
movements, what successes or failures have forecasters had in the use of
TAZ-to-TAZ CTPP data in an AM peak period UE traffic assignment?  Or some
variation that might include enhancements to the commuter flow data to
represent the (relatively small)  non-commuter AM Peak vehicle travel
and/or other adjustments to the CTPP?s representation of home-to-work
travel?  I am aware of one test that notes the ?lumpiness? of working
directly with the TAZ-to-TAZ level CTPP data (with the end result being the
%RMSE statistics do not look stellar), but am also aware of many
forecasters who manage to squeeze good value out of whatever ground
truth-based data is available.  I am reluctant to bring up the
?origin-destination matrix estimation? approach that can start with even a
seed matrix of 1?s in every TAZ to TAZ cell, but would be happy to hear of
any CTPP-based efforts where the study has summarized how the ?raw? CTPP
trip table matrix compares to the final adjusted ?seems to assign well?
matrix.

I am not expecting to see many responses that focus on use of CTPP in this
type of exercise, and suggest that you reply directly to this listerv
rather than just to me, since whatever info you might offer might inspire
others to comment.  But if there is some reason why that may be a problem,
I am happy to get your comments directly to the email noted below (and can
send to the full listserv without attribution to you).

Thanks in advance,

Ken Cervenka

Ken.Cervenka@dot.gov






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