- Annual Traffic Count Program
- Traffic Volume Forecasts
- Commuting and Travel Characteristics
- Transportation System Performance Measures
- 2005 Travel Demand Model Development Documentation
- Current and Historical Traffic Volume Forecasts
Annual Traffic Count Program
Pima Association of Governments, along with some of its member jurisdictions, regularly collect traffic counts on major roads and intersections throughout the region. In addition to being a vital input to PAG’s transportation planning and travel forecasting, traffic count information is used by:
- Transportation engineers and planners throughout the region to identify existing traffic problems and solutions
- The Arizona State Legislature and U.S. Congress to make decisions regarding the need for and allocation of state and federal funds
- Regional, state and federal air quality experts to monitor traffic related pollutants and conformance with air quality standards
- Private sector marketing specialists as measures of accessibility and exposure
To maximize the value of this data, PAG annually compiles and distributes all of the traffic counts collected throughout eastern Pima County. These data are available in a number of formats:
Additional traffic count data are available from:
PAG collects weekday traffic count data for selected regionally significant roadway segments and signalized intersections within the Tucson metropolitan area. PAG’s traffic count data is collected by a consultant firm, usually on a Tuesday, Wednesday or Thursday in the Spring or Fall. Typical traffic data collection methods involve the placement of pneumatic tubes connected to recording devices at selected locations along roadway segments for a period of at least 48 contiguous hours, and specialized video camera setups at intersections to capture turning movements of traffic for two hours in the morning and two hours in the afternoon when traffic peaks.
PAG’s goal is to collect a representative traffic count for each roadway segment. However, counting devices can and sometimes do malfunction, resulting in erroneous results. Nearby roadway construction, traffic accidents and other unknown incidents can significantly affect traffic and result in non-typical counts. Even without specific incidents, traffic counts can vary significantly at different locations within a given segment and from day-to-day, month-to-month and throughout the year.
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Traffic Volume Forecasts
Pima Association of Governments (PAG) maintains the regional travel demand models and databases to forecast the future travel, in support of the annual Transportation Improvement Program (TIP), Long Range Transportation Plan (RTP) development and a wide spectrum of other regional planning studies in the Tucson region.
Use of Information
- Although PAG’s regional travel demand model has been calibrated and validated using many traffic counts, much of the census and household survey data, and other available transportation data available in the PAG area, the forecasted traffic volume maps produced by PAG’s travel demand model are largely based on the best estimate of the population and employment in Tucson region at the time when the model was used, which are often subject to change. Therefore, please check back often for updated data and information.
- Information included in the maps may be downloaded from the links provided below and should be used for planning purposes only. If you have more recent data, it is strongly suggested that you make appropriate adjustments to the information based on your data as necessary.
- The download maps are in both ESRI's shapefile format, viewable with most GIS software and Google KML file format, viewable in Google Maps and Google Earth.
- Users are cautioned that the forecasts below are prepared for varying purposes and contain demographic and roadway network assumptions which may not be suitable for other purposes. The assumptions inherent in the forecasts can lead to significant differences in the forecast results. The user should understand those assumptions and exercise due caution before using the forecasts for other purposes.
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Commuting and Travel Characteristics
1990, 2000 (and coming soon 2006-2010 Five-Year) Pima County Journey-To-Work Data – the 1990 and 2000 Census and 2006-2010 American Community Survey ACS) collected and reported data on the commuting patterns and characteristics of workers 16 years and older.
PAG 2000 and 2010 Household Travel Survey – The objective of PAG’s 2000 and 2010 Household Travel Survey wereto obtain data about activity behavior and travel patterns of Tucson area households. The survey collected data on the activities and travel over a 24-hour period for all members of more than 2,000 households, a representative sample of the households in the Tucson area.
Tucson Transit 2004 Onboard Survey-- In October 2004, the City of Tucson conducted an On Board Origin and Destination Survey of the passengers on the fixed route transit services in Tucson, Arizona. The survey included the City of Tucson transit system (SunTran); the University of Arizona campus transit system (CatTran); and City of Tucson Inner City Express Transit (TICET) downtown transit service. The purpose of the survey was to collect data on the regional travel patterns and demographics of transit riders.
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Transportation System Performance Measures
Transportation System Performance Measures are important for assessing the effectiveness and efficiency of the transportation system as a whole so as to identify the proper multi modal solutions to the traffic congestion problems.
Pima Association of Governments (PAG) sets the programs to collect the traffic and travel data to develop performance measures for monitoring the current traffic congestion; employs the modeling and other techniques to forecast the travel pattern change and traffic congestion evolution; and, works with member jurisdictions to develop the transportation plans to mitigate traffic congestion in the region.
- Historical Urban Mobility Reports
- Volume-to-Capacity Ratios
- Travel Time & Speed
- Emergency Evacuation
1. Historical Urban Mobility Reports
The Texas Transportation Institute's Urban Mobility Reports use data from federal, state, and local agencies to develop estimates of congestion and mobility within urban area throughout the United States, including Tucson. The methodology developed by several previous research studies yields a quantitative estimate of urbanized area mobility levels, using generally available data, while minimizing the need for extensive data collection.
2. Volume-to-Capacity Ratios
Congestion also can be measured by a volume-to-capacity ratio (V/C Ratio). For the purposes of congestion calculations in this regional analysis, congestion levels are defined as:
- V/C Ratio greater than 1.0 = Severe Congestion
- V/C Ratio of 0.75 to 1.0 = Heavy Congestion
- V/C Ratio of 0.5 to 0.74 = Moderate Congestion
- V/C Ratio of less than 0.5 = Low or No Congestion
3. Travel Time and Speed
In 2003, Pima Association of Governments contracted with Carter & Burgess to collect data on roadway characteristics and field measured travel time and speed. Travel speed data was collected using the floating car method from April 2003 through June 2003 on Tuesdays, Wednesdays and Thursdays, during the morning and afternoon peak, and during the midday off-peak period. Intersection delay for through vehicles was recorded at signalized intersections to determine level of service. The study results are documented in the report titled 2002-2003 PAG Regional Travel Time & Travel Speed Study.
Currently, PAG is parterning with Metropia, Inc. to update the regional travel time and speed data.
4. Emergency Evacuation
The recent report titled Emergency Evacuation Report Card 2006 evaluates the 37 largest U.S. urban areas to identify the evacuation challenges facing planners and residents in each area. The report uses a computed “Evacuation Index” to score, grade and rank each urban area based on automobile accessibility, internal traffic congestion and the highway capacity of major exit routes. The report finds that 25 of the 37 “could face greater challenges than New Orleans experienced after Hurricane Katrina.” Tucson was not one of the 37 urban areas included in the report. However, the evacuation index for Tucson has been computed by Pima Association of Governments (PAG) using the report’s methodology, resulting in the following scores, grades and rankings:
- With the highest and best evacuation index score of 90.0, Kansas City is ranked No. 1 of the 38 urban areas, which earns it a grade of “A”
- New Orleans has an evacuation index score of 67.3, which earns it a grade of “D” and rank of No. 12
- Tucson has an evacuation index score of 63.5, which earns it a grade of “D” and rank of No. 16
Phoenix has an evacuation index score of 43.6, which earns it a grade of “F” and rank of No. 31 The methodology used for the Emergency Evacuation Report Card 2006 is relatively simplistic. And it can be argued that Tucson’s score, grade and rank should be worse than computed above because the report’s methodology does not take into account the distribution of Tucson’s population relative to the location and orientation of the Tucson’s major exit routes, and the physical constraints associated with getting Tucson’s population onto the major exit routes. Even so, the results of this study are useful because they highlight the very real issues and challenges facing many U.S. cities, including Tucson, in planning and preparing for a mass evacuation. Like the 25 urban areas identified in the report, Tucson too could face greater challenges than New Orleans experienced after Hurricane Katrina.
The following approach and data was used to compute the evacuation index for Tucson:
- Automobile Accessibility (AA) is an estimate of the percentage of the population that would be evacuated by car. Based upon the Katrina experience, it is assumed that all households that own a car (which includes 91 percent of Tucson households) will evacuate by car. In addition, it is assumed that one half of the households without a car (4.5 percent of Tucson households) will evacuate with relatives and friends who do have a car. Tucson’s Auto Accessibility score is 91 percent + 4.5 percent, or 95.5 percent (an “A”). In comparison, New Orleans’ score is 91 percent (an “A”) and Phoenix’s score is 96.4 percent (also an “A”).
- Internal Traffic Flow (ITF) is an estimate of the ability of the roadway system within the urban area to deliver traffic to the exit routes. The Texas Transportation Institute’s “travel time index,” a nationally recognized indicator of traffic congestion in U.S. urban areas, is used to measure and score internal traffic congestion for this study. Using this measure, Tucson has a score of 69 out of 100 (a “D”), compared to New Orleans’ score of 81 (a “B”) and Phoenix’s score of 65 (a “D”).
- Exit Capacity (EC) is a measure of the ability of major routes leading out of an urban area to accommodate the evacuating population. The standard for evaluation is 50% of the theoretical capacity of the roadways at the exit points over a 12-hour period, assuming use of contra-flow on the exit routes. Using this measure, New Orleans scored 67 out of 100 (a “D”), while Phoenix scored 25 (an “F”). The comparable score for Tucson is 64 (a “D”), which assumes I-10 EB, I-10 WB, I-19 SB, SR-77 NB and SR-86 WB can all be used as exit routes. However, Tucson’s score could be as low as 16 (an “F”) if, for example, only I-10 EB could be used as the primary exit route. Evacuation Index (EI) is used to score and rank each urban area, and is computed by averaging the Internal Traffic Flow (ITF) score and the Exit Capacity (EC) score, and factoring the result by the Auto Accessibility (AA) score: EI = ((ITF +EC) / 2) * AA. Tucson’s computed evacuation index score is 63.5.
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PAG Travel Demand Model Development Documentation (2005)
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