Re: [UrbanSim-Users] travel_data

Essentially, you just need to put into the table travel_data, a
from_zone, to_zone, and whatever travel model skim variables you want to
use. We use travel times in the am peak by drive alone, transit walk,
and walk modes, in some applications, to compute the number of jobs
reachable within 30 minutes, for example. We also use generalized
costs, if available. Numerous variables are already defined that use
these times and generalized costs, in the psrc and semcog applications,
for example.

I'll look into putting these applications into the installer we are
going to release shortly.

Paul

Jen Duthie wrote:
> Hi,
>
> Can someone please help me figure out how to alter the code to use
> travel times instead of logsums? Exactly which files need to be
> altered, and how should they be altered?
>
> Thanks,
> Jen
>
>
> Paul Waddell wrote:
>
>> UrbanSim is generally connected to an existing regional travel model,
>> from which either composite utilities from the mode choice model (aka
>> logsums) or more generally, congested travel times by mode for the
>> home-based-work purpose in the a.m. peak period (or other similar
>> measures) are extracted for each travel model year. The connections can
>> be automated - we have done this with emme/2 and transcad most recently,
>> and previously with TP+ and Minutp. It essentially requires an
>> interface to be written for whichever travel model you are using, to
>> summarize UrbanSim output and generate the inputs required for the
>> travel model; and in the other direction, to extract travel model
>> outputs and generate the travel_data table -- with whatever travel
>> measures you want to use. Logsums are by no means required, and we have
>> found them to be somewhat unstable in practice (though they look good in
>> theory) - with small changes in the travel model causing large shifts in
>> the logsum measures and therefore precipitating a recalibration of UrbanSim.
>>
>>
>>
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Received on Tue Aug 14 2007 - 08:33:12 PDT