In the first TMIP-sponsored peer review, ADOT sought feedback and recommendations from a panel of experts on several facets of ADOT's statewide model and model development plan. The following topics were covered, with panel members providing guidance:
The discussion and panel's recommendations on these topics are documented in Arizona Department of Transportation (ADOT) Travel Model Peer Review Report (FHWA-HEP-12-024).
During the second peer review, ADOT provided the following summary of the progress made to date on the recommendations from the first peer review.
First Review Panel Recommendation
The panel recommended applying a local bus abstraction method in AZTDM3. The panel commented that the use of an abstraction method to estimate local transit in a statewide model was acceptable practice since the model would be used to test regional transit demand and not to estimate local ridership or local transit route choice. Employing a transit abstraction method would reduce network coding at a statewide scale. The panel also recommended following a pre-established structure when developing the local transit abstraction methods. The panel concurred with the practice of only using similar transit service types in an abstraction set when doing transit abstraction. Transit services with different characteristics (e.g., local bus vs. express bus) should not be combined in the same abstraction.
ADOT Response
The third generation statewide model (AZTDM3) has implemented the local transit service abstraction method.
First Review Panel Recommendation
The panel recommended that ADOT stop vehicles-if they are allowed to do so-in reference to conducting a statewide cordon study. For low-volume roadways, ADOT could stop traffic in the lane. For interstate or higher-volume facilities, ADOT could stop a sample at a designated area, such as a rest stop. If ADOT is not allowed to stop vehicles, then the panel recommended conducting a license plate survey. However, when conducting a license plate survey, the panel strongly recommended that ADOT not conduct a mail-in follow-up survey due to the panel's previous experience with inconsistent data and negative public reaction. The panel also recommended that ADOT review potential new technologies, such as cell phone or Bluetooth, as these may provide an alternative method to collect important data if vehicles cannot be stopped.
The panel also recommended that ADOT collect better household data in the rural areas of the state and better data for long-distance trips. The panel recommended stratifying the sampling plan by geography (e.g., by county) and by hard-to-reach groups (e.g., minorities or long-distance travelers). The panel suggested that ADOT could conduct a preliminary sample design study as a low-cost method for determining the number of samples needed.
The panel also recommended that ADOT explore opportunities to partner with local MPOs to pool data collection efforts. Partnering with the MPOs would facilitate more efficient data collection and greater consistency between data sources.
ADOT Response
ADOT partners with the MPOs to incorporate MPO model data into the statewide model. For instance, ADOT is using the latest network and socioeconomic data provided by the MPOs in the AZTDM3.
ADOT is planning to participate in the 2015 National Household Travel Survey (NHTS). An add-on of 2,000 samples is being considered to collect travel behavior data for the greater Arizona area residents belonging to smaller MPOs and urbanized areas outside the larger MPOs as well as rural and tribal areas. Consideration will be given to equipping all recruited households with GPS devices. ADOT is also considering conducting a long-distance survey as part of this effort. The add-on to the survey sample will also consider market-augment sampling.
ADOT reported that long-distance travel survey data has been elusive. Trips in existing databases, such as the 1995 American Travel Survey, are higher than counts and needed adjustments have been difficult. Some states do not have data and the 2002 NHTS data has not been good enough for application. ADOT is still searching for a viable, cost-effective approach to collect long-distance travel data. ADOT is considering purchasing cell phone data and is looking for recommendations, especially since much of the long-distance travel is from non-Arizona residents.
ADOT researched whether they would be able to stop vehicles for a state-sponsored cordon survey and were informed that this practice was unlawful. The cordon survey was canceled due to complexity of collecting the data. ADOT will look at the border survey data they have obtained to determine to what degree it may be useful in identifying long-distance trips.
First Review Panel Recommendation
The panel liked that the AZTDM2 borrowed MAG's short-distance freight model and recommended that ADOT use MAG's freight data to complement the FAF3 data in recalibrating their freight models.
The panel commented that commodity-based mode choice modeling for freight can be difficult. The panel recommended that ADOT begin by defining the questions they would like to answer with a freight model, such as:
The panel recommended scaling the complexity of the truck mode choice model to meet their needs based on the questions being asked of the model. The panel also commented that ADOT should be able to take advantage of the TRANSEARCH commodity database purchased regardless of the complexities chosen for the development of the freight mode choice model.
ADOT Response
ADOT reported that the short-distance truck model from MAG was used to recalibrate portions of the statewide freight model. ADOT also reported that the effect of trucks on the highways is addressed by passenger-car equivalents and terrain variables in the statewide truck model.
ADOT is using TRANSEARCH data in place of FHWA FAF3 commodity flow data in the AZTDM3. As of the AZTDM2, the question of which dataset to use had not been decided. FHWA is proposing to release the next FAF dataset version at the county-to-county level (probably in late 2015). ADOT will reassess the FAF/TRANSEARCH issue after the new FAF dataset release. ADOT is also looking at video tracking of trucks (or other technology) to obtain a better estimate of truck flows.
First Review Panel Recommendation
The panel thought that building a hybrid statewide/local model was a good idea and strongly recommended that ADOT pursue this development. The panel concurred with ADOT's recommended approach of maintaining data at a more disaggregate level. The panel also recommended that ADOT look at creating a "window out" tool that could be used to perform the sub-area extraction from the statewide model.
ADOT Response
The AZTDM3 has about 6,100 zones. For the sub-area model development, ADOT has developed a regional analysis zone system that aggregates the AZTDM TAZ to 482 regional analysis zones and 37 super districts to aid in sub-area modeling. Focus area model development is also underway for Central Yavapai MPO (CYMPO) and Central Arizona Governments (CAG).
First Review Panel Recommendation
The panel recommended that ADOT link the development of advanced modeling techniques to specific needs. They recommended that ADOT consider links to both state and national economic models when looking at connections between the statewide and economic models. The panel also recommended looking into dynamic traffic assignment (DTA) due to the long distances in state travel. However, the panel commented that ADOT needed to specify the functions that would be performed by a DTA and that they would need to be clear on the functional specifications. A statewide DTA application would require development of a simplified approach that extracts the salient portions, such as time of day. The panel also recommended that ADOT consider collecting more detailed highway network data, such as signal locations and timing plans, in anticipation of implementing a DTA.
The panel recommended that ADOT consider an open architecture to implement any activity-based (AB) model platform if ADOT decides to use an AB model. The panel also commented that an AB model approach would most likely also entail an investment in resources and acceptance of longer runtimes.
ADOT Response
As a whole, ADOT seeks to evaluate transportation project impacts with the statewide model with the following quantitative performance measures:
ADOT also wishes to use the statewide model for modernization projects affecting traffic flow, including:
ADOT is exploring applying for Strategic Highway Research Program (SHRP2) C10 to help determine which policy options would be inadequately addressed by a traditional 4-step model and that might be better addressed by an AB model or DTA model. MAG's Inner Loop Traffic Operations model and AB model efforts or the FHWA exploratory advanced research in SimTravel may also provide helpful insights.
ADOT is also looking at using the state's REMI TranSight model to quantify the economic contributions of transportation investments.
Regarding collecting more data for DTA, ADOT is planning to collect more detailed network data in the next phase of the AZTDM model improvement.
