Travel Time & 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.
Urban Mobility
Traffic congestion continues to worsen in American cities of all sizes, creating a $78 billion annual drain on the U.S. economy in the form of 4.2 billion lost hours and 2.9 billion gallons of wasted fuel—that's 105 million weeks of vacation and 58 fully loaded supertankers. These are among the key findings of the Texas Transportation Institute's 2007 Urban Mobility Report. The current report is based on 2005 figures, the most recent year for which complete data was available.
The 2007 mobility report notes that congestion causes the average peak period traveler to spend an extra 38 hours of travel time and consume an additional 26 gallons of fuel, amounting to a cost of $710 per traveler. Along with expanding the estimates of the effect of congestion to all 437 U.S. urban areas, the study provides detailed information for 85 specific urban areas, including Tucson. The report also focuses on the problems presented by "irregular events"—crashes, stalled vehicles, work zones, weather problems and special events—that cause unreliable travel times and contribute significantly to the overall congestion problem. Worsening congestion, the study notes, is reflected in several ways:
· Trips take longer
· Congestion affects more of the day
· Congestion affects weekend travel and rural areas
· Congestion affects more personal trips and freight shipments
· Trip travel times increasingly are unreliable
The report identifies multiple solutions to the congestion problem that, researchers say, must be used together to be effective. These include:
· Get as much service as possible from existing infrastructure
· Add road and transit system capacity in critical corridors
· Relieve chokepoints
· Change usage patterns
· Provide choices
· Diversify the development patterns
· Keep expectations realistic
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. |