Fw: [TMIP] Re[2]: [TMIP] Static assignment vs. DTA in freeway capacity planning

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Fw: [TMIP] Re[2]: [TMIP] Static assignment vs. DTA in freeway capacity planning

________________________________
From: paul balmacund
Sent: Monday, April 1, 2019 4:45 PM
To: jchoi
Subject: Re: [TMIP] Re[2]: [TMIP] Static assignment vs. DTA in freeway capacity planning

Dan, Maricopa MAG:

I would like to humbly comment on the SPINE Study, referenced in the following study and resulting paper:

"REGIONAL MICROSIMULATION AS A TOOL FOR IMPROVING PROJECT EVALUATION AND CUTTING THE COSTS OF MICROSIMULATION STUDIES"

I agree that the use of corridor subarea trip-tables from the regional microsimulation is the general way to start. In general, these “seed” trip-tables are then validated to the detailed counts (via ODME etc), speeds, queues, etc in the corridor subarea microsim network. However, there is generally an issue with the process of trip-table matrices validation, especially when the focus is on highway operations on an extended length of freeway, and where most of the trips in the entire subarea microsim use the freeway (get on/off). I would wager that more than 75% of the total 4-hour AM period trips in the SPINE study’s traffic microsim network would have used the freeway. So therefore, I think that it would be necessary for the freeway ramp-to-ramp O-Ds to be validated based on vehicle class O-D survey data. Remember, the O-D extracted from the regional microsim model is “modeled” data and is not “real” O-D data.

Real ramp-to-ramp data is necessary for freeway ramp-to-ramp O-D validation in the corridor microsim model. When vehicles get on the freeway at an on-ramp, they know their destination off-ramp, and as such “at most times” get into the best lane(s) and then follow exit ramp signs to change lanes to get to the desired off-ramp. However, this is the probable behavior for the defensive driver, and not the aggressive driver who changes lanes frequently, and jockeys for position, etc. Now, if the freeway ramp-to-ramp O-D vehicle volumes are validated, then the simulation would be more accurate than by just validating ramp and mainline volumes alone. These latter volumes may be “validated” adequately (assn vols versus counts), RMSEs, etc, but the ramp-to-ramp ODs may be incorrect, leading to incorrect weaving, merging, and diverging traffic operations. Literally, this means that the vehicles would not have had the correct ramp-to-ramp O-D intelligence, and as such may have exhibited incorrect car-following and lane-changing behavior, and possibly resulting in a less-than-correct base-year simulation validation.

Paul Balmacund

Unemployed consultant

"Sunlight is the best disinfectant" - Justice Louis Brandeis (1856-1941)

________________________________
From: janet=caliper.com@mg.tmip.org on behalf of jchoi
Sent: Monday, April 1, 2019 11:16 AM
To: TMIP
Subject: Re: [TMIP] Re[2]: [TMIP] Static assignment vs. DTA in freeway capacity planning

To follow up on Dan Morgan's posting, here is an article from this year's TRB that discusses recent developments in regional microsimulation and DTA in the Phoenix, AZ area.

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Janet Choi | Senior Transportation Planner
Caliper Corporation • 1172 Beacon Street, Suite 300 • Newton MA 02461 • USA
Phone: 617-527-4700 • Fax: 617-527-5113
www.caliper.com

Attached files:
MAG_Regional_Microsimulation.pdf
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