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Travel Demand Modeling


The Alamo Area Metropolitan Planning Organization (AAMP) develops and maintains a full set of Travel Demand Models (TDMs) for the region. The TDB efforts cover Bexar, Comal, Guadalupe, Kendall and Wilson Counties. These counties are the AAMPO Modeled Counties. The TDMs provide the primary means for identifying existing and future transportation system deficiencies and for assessing proposed regional mobility improvements. The models are suitable for the following applications:

  • Analysis of Transportation Systems for Short and Long Range Planning
  • Evaluation of Regional Transportation System Improvements
  • Identification of Transportation System Deficiencies
  • Conducting Alternatives Analyses, Corridor Studies or Subarea Studies
  • Providing Traffic Statistics for estimating Highway Performance Metrics
  • Interfacing with US EPA Emissions Software (MOVES-Motor Vehicle Emissions Simulator) to Estimate On-road Mobile Source Emissions for Urban Airshed Modeling and AQ Conformity Analyses

The current TDM, known as San Antonio Multimodal Model, version 5.0 (SAMM5.0) is being updated (to SAMM5.1) for improved ease of operation. The models also incorporate a new Master Network System that improves project tracking and project annotations required for Air Quality Conformity analyses as well as a new network editing process. SAMM5.0 continues to be used for evaluating alternative demographic scenarios as well as alternative highway and transit systems as part of the Transportation Improvement Process (TIP) and the Metropolitan Transportation Plan (MTP).

AAMPO’s TDM is a traditional 4-step model including Trip Generation (Tripcal6), Trip Distribution (Destination Choice), Mode Choice (Nested Logit) and Traffic Assignment (TransCAD MMMC User Equilibrium). The SAMM 5.0 assignment model runs individual traffic assignments for each time period, which are then combined to produce 24-hr daily traffic volumes. The model features Speed Feedback and produces time-of-day directional forecasts for 4 daily time periods: AM-Peak, Midday, PM-Peak, and Overnight.

The SAMM5.0 TDM is calibrated and validated to new travel data (including 2020 pre-Covid-19 traffic counts and transit ridership, as well as 2018-2019 travel surveys: Workplace, Commercial Truck, External, Airport, and Special Traffic Generators), with a Short-Range Forecast for 2030, a Mid-Range Forecast for 2040 and a Long-Range (MTP) Forecast for 2050. Intermediate forecasts are also available for 2025, 2035, and 2045. The AAMPO Transportation Policy Board voted to approve the Mobility 2050 Plan in June 2022.

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Traffic Analysis Zone - with MPO-related layers

The demographic databases are composed of population, households, household income, and employment inventories for each traffic analysis zone (TAZ) comprising the AAMPO Modeled Counties. TAZs are the geographic units used to inventory existing and future demographic data required for modeling purposes. Typically, a TAZ structure is developed consistent with the defined roadway structure. This is accomplished by allowing network roadways to be the primary definition of TAZ boundaries and attempting to minimize roadways that traverse individual TAZs. The rationale for such a structure definition is the model will perform better by providing trips comparable access opportunities to adjacent streets and transit lines.

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Highway Network - with MPO related layers

Updated on 03/03/2023

In 2023, AAMPO regional models were re-calibrated and re-validated to base year 2020. The 2020 base year network, along with 2025, 2035, 2045 and 2050 Transportation Improvement Program (TIP) and Metropolitan Transportation Plan (MTP) forecast networks, are available for downloading in TransCAD or ArcGIS formats.

The region’s highway networks, which are coded for use by the Travel Demand Model SAMM 5.0 covers AAMPO’s Modeled Counties. These counties include Bexar, Comal, Guadalupe, Kendall, and Wilson. The highway networks are generally considered to represent all roadways classified as collector and above within the Functional Classification system. Specific roadway attributes for the coded networks include Functional Classification (FUNCL), Facility Type (FTYPE), Direction (one or two-way), Area Type (AT), Lanes, Street Name, County, Traffic Analysis Zone (TAZ), Speeds, Capacity, Counts, Modeled or Projected Volumes, Travel Times, and HOV/Toll designations where applicable. For modeling purposes, the roadway networks are used to estimate travel time skims (Daily or by four Time-of-Day Periods) for each TAZ to all other TAZs (1359x1359). Travel time skims are indicative of accessibility, thus affecting travel orientation and traffic patterns.

Disclaimer: Locally adopted TIP/MTP networks, but not officially conforming to AQ standards, pending FHWA approval

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Transit Network – with MPO related layers

Updated on 03/03/2023

Transit Networks for 2020, 2025, 2035, 2045, and 2050 have been developed and are available for download. The 2020 transit system, which operates almost exclusively along mixed flow highway links, consists of 60+ bus routes for various bus modes including Metro, Frequent, Express, Skip, and Primo. Future year transit networks may contain additional premium modes of transit.

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