Products, Services, and Data

Regional Travel Demand Modeling

COMPASS uses a travel demand forecast model to estimate average weekday and peak hour demand for the transportation system in the Treasure Valley. The model can show where congestion may occur in the future, as well as other measurements such as travel time and congested speed. The model outputs are used to test and help plan future transportation projects, support the Ada County Highway District's impact fee program and Capital Improvement Plan, conduct air quality conformity demonstrations, review the potential impacts of proposed developments and traffic impact studies, and respond to various other special member requests. 

The information below summarizes the geography covered by the model, model characteristics, and a history of use of travel demand modeling in Ada and Canyon Counties.

A major update to the regional travel demand model was completed in January 2015. 

Model Geography

  • Ada and Canyon Counties, Idaho
  • Population: 581,288 people (2010 Census)
  • 1,800 centerline miles represented in the model network
  • 2,062 Traffic Analysis Zones (TAZs)
    • 1,308 in Ada County
    • 754 in Canyon County

Model Characteristics 

  • Four-step trip-based model 
  • Mode choice step added in 2005, updated in 2010
  • Forecast three time periods - daily, 4 pm to 5 pm, and 5 pm to 6 pm
    • Additional time period – 7 am to 8 am – is underway
  • Major update (calibration and validation) to 2011/12 conditions was completed January 2015.

Model History (1975 – 2012)

2010s
In 2012, COMPASS began another update of the regional model brought on by rapid growth and the need to update local data. The update process and model inputs were reviewed and accepted by TMAC in June 2004. Some characteristics of this model are as follows:

  • Ada and Canyon Counties
  • Estimated population: 581,288 (2010 Census)
  • Average number of person  trips per household: 10.55
  • Six trip types (work, shop, social/recreation, school, other, and non-home)
  • 2,062 traffic analysis zones
  • Included interstates, highways, principal and minor arterials, collectors, and a few local roads for connectivity purposes
  • Forecasts available for average weekday, peak hours:5 pm to 6 pm; 4 pm to 5pm

A household travel survey was conducted in fall 2002 to provide data for this model. Over 3,600 households participated in this survey. 

Documentation of the 2012 calibration of the regional travel demand model is available in the following report:

2000s
In 2002, COMPASS began another update of the regional model brought on by rapid growth and the need for more local data. The update process and model inputs were reviewed and accepted by TMAC in June 2004. Some characteristics of this model are as follows:

  • Ada and Canyon Counties
  • Estimated population: 480,000 (2002)
  • Average number of person  trips per household: 11.1
  • Six trip types (work, shop, social/recreation, school, other, and non-home)
  • 534 traffic analysis zones
  • Included interstates, highways, principal and minor arterials, collectors, and a few local roads for connectivity purposes
  • Forecasts available for daily and peak hour (5 pm to 6 pm)

A household travel survey was conducted in fall 2002 to provide data for this model. Over 2,500 households participated in this survey. 

Documentation of the  2002 calibration of the regional travel demand model is available in the following report and appendices:

Late 1990s
After review of the 1995 model and the tremendous growth occurring to the west, the Ada Planning Association chose to develop a two-county traditional three-step model.
In 1998, the Ada Planning Association completed the first household travel characteristics survey for both counties. Over 1,800 households participated. Detailed travel logs were kept for household members over 15 years of age and a general one was kept for members under 15 years of age. The first two-county three-step model was developed using these data. Some characteristics of this model are as follows:

  • Ada and Canyon Counties
  • Estimated population: 378,013 (1997, Ada Planning Association)
  • Average number of trips per household: 10.0
  • Four trip types (work, shop, other, and non-home)
  • 463 traffic analysis zones
  • Included interstates, highways, principal and minor arterials, and collectors

(Documented in 1997 Travel Model Calibration Report, COMPASS, September 2001)

This was the first two-county model accepted by TMAC, and was used from June 1999 and until 2004. Also in 1999, the Ada Planning Association became the Community Planning Association of Southwest Idaho (COMPASS), when it began to serve as the metropolitan planning organization for both the Boise and Nampa urbanized areas.

Early 1990s
In 1995 Ada County became a “beta test site” for a tour base model and it was one of the first applied by a metropolitan planning organization. Some of the characteristics of this model are as follows:

  • Ada County
  • Estimated population: 241,201 (1994, Intermountain Demographics )
  • 285 traffic analysis zones
  • Included interstates, highways, principal and minor arterials, and collectors
  • Incremental Model-Destination Choice Model
  • Planning application: Bench/Valley Study commissioned by Ada County Highway District

1980s
Sometime in the early 1980s, the model and demographic responsibilities were given to Ada Planning Association, the metropolitan planning organization for Ada County. The 1975 model was refined and recalibrated using 1980 census data and updated traffic counts. Some characteristics of the 1980 model and area are as follows:

  • Ada County
  • Estimated population:  173,036 ( 1980 Census)
  • Estimated vehicle miles of travel: 2,786,450
  • 265 traffic analysis zones
  • Included interstates, highways, and principal and minor arterials
  • Used a gravity based method

The 1980 model was used for about 10 years. This model was developed using UTPS software and converted to TranPlan in the early 1990s.

(Documented in Transportation Model Recalibration Report 1980, Ada Planning Association, March 1985)

1970s
Travel demand forecast models are not new to the State of Idaho, especially in Ada County. The earliest record of a travel demand model for Ada County is 1975. At this time, the model and demographics were developed and managed by Idaho Transportation Department. Some characteristics of the 1975 model and area are as follows:

  • Boise Urbanized Area
  • Estimated population:  108,000
  • Estimated vehicle miles of travel: 1,021,760
  • Average number of trips per household:  6.3
  • 240 traffic analysis zones
  • Included interstates, highways, and principal and minor arterials
  • Used a gravity based method
  • Included modal choice and time of day estimates

(Documented in Boise Urban Area Transportation Planning Model, COMSIS Corporation, December 1978)