Short description
The Travel Survey was completed in 2003 and was used to support transportation model improvements for the 2004 and 2008 Regional Transportation Plans and other transportation studies.  It was a survey of the daily travel habits of households within six counties of Southern California (Imperial, Los Angeles, Orange, Riverside, San Bernardino and Ventura.  Surveys of this magnitude are conducted about every ten years.  The previous survey was conducted in 1991.  The next travel survey was conducted in  the year 2011.  The Southern California Association of Governments (SCAG) contracted Nustats, a nationally recognized research firm, to conduct the travel survey.  The survey was funded by SCAG,  LACMTA, Caltrans, RCTC, SANBAG and the California Air Resources Board.
The survey provides valuable travel characteristics to agencies responsible for planning and improving roads, carpool lanes, trains, buses and other features of our transportation system.  It sheds light on how that system is being used and by whom. For example, electronic sensors can tell you the condition of your favorite freeway; but only through travel surveys do we get a sense of how many freeway trips are destined to nearby supermarkets, or perhaps to distant places of work. Transit agencies, likewise, use travel surveys to plan bus service between popular places.  The Survey provides critical travel behavioral information and demographic data needed by SCAG to update the Travel Demand Model.
Caltrans and MPOs in the State conduct travel surveys every ten (10) years to obtain detailed information about the household socioeconomic characteristics and travel behavior of households statewide.  The purpose of the 2010 California Household Travel Survey (2010 CHTS) is to update the statewide database of household travel behavior that is used to estimate, model and forecast travel throughout the State.  The 2010 CHTS will provide short and long-distance trip information that will be used for the development of travel demand and land use models.  The 2010 CHTS data is essential to the development and calibration of regional travel demand models for transportation planning and to assist in the forecasting of greenhouse gas (GHG) and criteria pollutant emissions.
A primary goal of the 2010 CHTS program is to coordinate and/or combine the travel survey efforts by the State, MPOs, and Regional Transportation Planning Agencies (RTPAs) so as to benefit all.  This coordinated/combined effort will help ensure data consistency throughout the State and will better guarantee an efficient use of the pooled funds. The State, Caltrans, and regional agencies have organized a Steering Committee to guide the implementation of the 2010 CHTS.  A Steering Committee representing MPOs, RTPA’s, the California Association of Council of Governments (CALCOG), and various state agencies was organized to create the Scope of Work and Request for Proposal to retain a consultant to perform the technical aspects and implementation of the survey for the 2010 CHTS program.  To implement the survey, Caltrans engaged a competitive procurement process to acquire consultant services. As a result of this procurement, NuStats, LLC (NuStats) was selected to conduct the 2010 CHTS. SCAG also selected a Consultant (Abt-SRBI) to conduct additional surveys and gather additional detailed demographic and travel behavior data within the SCAG Region. 
As the improvement of air quality has become increasingly critical to the SCAG region, the ability of SCAG to accurately predict the impacts of transportation improvements and air quality mitigation measures has become more important. Accurate air quality analysis requires accurate predictions of both traffic volumes and traffic speeds. Travel demand models, like the one employed by SCAG, have typically focused on predicting demand accurately, not speed. Speed has traditionally been an input that demand modelers adjusted as necessary to improve the accuracy of the volumes forecasted by the model. Consequently federal and state regulatory agencies have shown an increasing interest in the validation of both the volume estimates and the speed estimates produced by demand models. The project objectives of the Arterial Speed Studies are listed below:
1)     The primary objective of the first Speed Study was to test various low cost data collection techniques for measuring speeds against the “floating cars” method.  By collecting speed and other data simultaneously at a pilot test location, different methods of speed estimation can be compared and calibrated to determine the most accurate and cost effective methods available for more widespread use across the SCAG region.
2)     Building the comprehensive database of measured speeds and volumes needed for developing new volume delay functions, validating model speeds, and tracking speed changes over time.
3)     Develop and test new volume delay functions for both arterials and freeways.

SCAG hired Rea & Parker Research to provide consultative assistance to this endeavor and to develop a survey database of cross-border travel on weekdays and weekends by pedestrians, passenger vehicles, and commercial trucks. This database included the following cross-border characteristics, among others: 

  • Trip origin/destination (including geocoded SCAG region locations);
  • Trip purpose;
  • Travel Route;
  • Vehicle Type;
  • Trip Frequency; and
  • Traveler Characteristics. 
Also to be gathered were traffic counts that were conducted concurrently with the survey, including transportation mode classifications by quarter-hour and direction. The surveys and counts were performed at all Imperial County border crossings—Mexicali/Calexico Downtown, Calexico East, and Algodones (Andrade) … near Yuma, Arizona.
Surveys and counts were performed on selected weekdays and weekend days between February 5, 2007 and March 11, 2007. Counts were made for passenger vehicles, pedestrians, trucks, and buses northbound and southbound. Pedestrian surveys were administered northbound and southbound at Mexicali/Calexico Downtown and Algodones by interviewers who interviewed stopped vehicles passengers and pedestrians as they approached or just completed crossing the border. There were separate personnel assigned to count and to survey at each site. Truck surveys were administered northbound and southbound at Calexico East. Surveys were administered to passenger vehicles northbound and southbound at Mexicali/Calexico Downtown and northbound only at Calexico East and Algodones. The southbound surveys at Mexicali/Calexico Downtown were limited to rush hour periods and times when CALTRANS personnel could otherwise stop traffic. For other times at Mexicali/Calexico Downtown and at the other two crossings, southbound traffic moves unimpeded, making it impossible to conduct intercept surveys.



This Peer Review focuses on SCAG’s model development program and the validation of the 2008 Regional Travel Demand Model for Southern California. The Model is being updated for use in preparing the 2012 Regional Transportation Plan (RTP). This was the fourth in a series of peer reviews conducted for the Southern California Association of Governments (SCAG) Regional Travel Demand Model. The meetings for the fourth Peer Review were held on June 27-28, 2011 in the Los Angeles offices of SCAG. An introductory teleconference among Peer Review panel members was conducted on May 26, 2011.

The Peer Review panel’s primary objective was to review the model development program, validation tests and results, expert panel discussions, and overall model enhancement effort for validity with regard to state of the practice so that the model can be applied with sufficient reliability in the regional transportation planning process. The panel’s recommendations for: 1) short-term enhancements related to the use of the model in developing the 2012 RTP and 2) longer-term model enhancements for the next RTP in 2016 are summarized in the Peer Review #4 Report.  The Model is managed and operated by SCAG with development assistance from private consulting firms and academic institutions.  Expert panels have overseen the development and enhancement of specific modeling components. The Peer Review panel was assembled to review SCAG’s overall model enhancements and validation process.

In preparation for the Year 2008 validation of the regional travel demand model of the Southern California Association of Governments (SCAG), a Regional Screenline Traffic Count Program was conducted to establish the validation traffic count dataset. This effort entailed obtaining and reviewing existing traffic counts taken by SCAG’s member governments and stakeholder agencies, prioritizing and collecting traffic count data needs, developing a regional traffic count database, and conducting an analysis of count data to apply annual, seasonal, and other factoring to prepare the counts for the validation effort. The Regional Screenline Traffic Count Program was conducted in 2009.

The final traffic count database prepared through this effort includes traffic counts by time-of-day, vehicle classification, and in some cases, occupancy for freeways and high occupancy vehicle (HOV) lanes in the six-county SCAG region. The focus of this effort was to establish validation counts for roadways that cross screenlines, although counts for non-screenline locations are included as well where data was available and resources provided. The final data includes adjusted 2008 average annual April/May/June traffic for all screenline locations by vehicle type and time period. For the Coachella Valley, peak season winter counts are also established.

The 2010-2012 California Household Travel Survey (CHTS) was a unique statewide, collaborative effort to gather travel information needed for regional and statewide travel and environmental models using the same instrument and methods across the state. Led by the California Department of Transportation (Caltrans), the survey was jointly funded by the California Strategic Growth Council, the California Energy Commission (Energy Commission), and eight transportation planning agencies across the state. Guidance and direction for the survey effort was provided by an Administrative Committee, composed of representatives from the funding agencies, and a Steering Committee composed of all stakeholders, including the California Air Resources Board, the California Department of Public Health, the California Department of Housing and Community Development, and all transportation planning agencies.