For More Information
- Can I download the report from the internet?
Yes. Link to: http://mobility.tamu.edu/ums/report/.
- What does “cost of congestion” mean?
Value of extra travel time (which we call delay) and the extra fuel consumed by vehicles traveling at slower speeds. Travel time has a value of $17.67 per person-hour and $94.04 per truck-hour in 2014. Fuel cost per gallon is the average price for each state.
- Why are some of the measure values different in this report compared to last year’s report?
The calculation procedures used for the 2015 report are different than in the 2012 report. The new procedures were used to re-calculate all of the historical values such that the delay and fuel amount and cost trend information is correct.
- What is the Travel Time Index?
The ratio of the travel time during the peak period to the time required to make the same trip at free-flow speeds. A value of 1.30, for example, indicates a 20-minute free-flow trip requires 26 minutes during the peak period (20 minutes × 1.30 = 26 minutes). The Commuter Stress Index is the same as the Travel Time Index but is based only on peak direction travel only.
- What is the Planning Time Index?
A travel time reliability measure that represents the total travel time that should be planned for a trip. Computed as a ratio of the 95th percentile travel time during the peak period to the time required to make the same trip at free-flow speeds. Computed with the 95th percentile travel time, it represents the amount of time that should be planned for a trip to be late for only 1 day a month. Computed with the 80th percentile travel time (PTI80), it represents the amount of time that should be planned for a trip to be late for only 1 day a week. A PTI of 3.00 means that for a 20-minute trip in light traffic, 60 minutes should be planned (20 minutes × 3.00 = 60 minutes).
- Where should I look for national data and trends?
Look at the Summary Tables – Congestion Levels and Trends.
- Where is the information about MY city?
Here’s the link: http://mobility.tamu.edu/ums/congestion-data/. There are multiple pages of trend data about your city.
- How did you pick the 101 intensively studied urban areas?
We have all of the urban areas with more than 500,000 people. We have several smaller cities, mostly chosen by the previous report sponsors. This is not a representative list.
- Which one of these tables has the information that I need to know?
We strongly suggest that you examine all the measures. The Delay per Auto Commuter, Cost per Auto Commuter, Travel Time Index and Planning Time Index are estimates of the congestion effects on individuals. Total Delay or Total Cost identifies the size of the congestion problem in the urban area. The change in values over time indicates the rate of growth or decline.
- Where does my city rank?
The city data tables show performance measure trends for several measures. Readers should compare ranking changes and performance measure values. In some performance measures a small change in the value may cause a significant change in rank from one year to the next. This is the case when there are several regions with nearly the same value (i.e., 15 hours is only 1 hour more than 14 hours). It is also important to look at trends. The multi-year performance measures are better indicators, in most cases, than any single year.
- What do you mean “There are several different rankings?”
There are several congestion measures and each has a use and a significance. There is no single, best measure. There are rankings for each measure.
- Do you have an answer to any of the criticism of the methodologies and results?
We have posted a response to criticisms at http://tti.tamu.edu/documents/TTI-2016-14.pdf.
- What are the titles of the researchers?
Tim Lomax: TTI Research Fellow
David Schrank: Research Scientist
Bill Eisele: Senior Research Engineer