- What does TVT mean?
TVT is the abbreviation for Traffic Volume Trends. It is a monthly publication by the Federal Highway Administration (FHWA) Office of Highway Policy Information.
- What type of information does TVT have?
TVT reports vehicle miles traveled (VMT) on all U.S. public roads on a monthly basis. VMT change rates are also reported. The geography is done by individual State.
- When is the monthly TVT report published?
The TVT report is published within 60 days after the close of the given month. You can get a copy of the report by visiting the web link at http://www.fhwa.dot.gov/ohim/tvtw/tvtpage.cfm.
- Can you notify me when a new TVT report is posted on your website?
Yes. You need to sign up at http://www.fhwa.dot.gov/policyinformation/travel_monitoring/tvt.cfm. Click on the eSubscribe button that is near the top of that page.
- Where did the FHWA get the traffic data used in TVT?
The TVT report is based on traffic data from the Highway Performance Monitoring System and on data submitted to the FHWA by State highway agencies throughout the entire U.S. The State highway agencies collect the data through permanent automatic traffic recorders (ATR) on public roadways.
- When should State highway agencies submit their permanent ATR data to FHWA?
Monthly permanent traffic recorder data should be submitted to the FHWA within 20 days after the closing of the month. For example, the January 2008 data should be submitted to FHWA no later than February 20, 2008.
- How does the FHWA compute VMT for a missing State in the TVT report?
In the event that a State does not have a traffic counter on a given functional classification of roadway, the TVT procedure is to estimate the missing value(s) from other functional classes from the same State. If the State does not have any valid values, the average value from the surrounding States for the same roadway functional class is used. If no surrounding State/States data are available, National average(s) are used.
- What is TMAS and how do I get access to it?
TMAS stands for Travel Monitoring Analysis System. TMAS provides online data submitting capabilities to State traffic offices to submit data to FHWA. Access to TMAS is obtained through the FHWA Division office in the individual State. This link provides contact information to all the Division offices: http://www.fhwa.dot.gov/field.html#fieldsites.
- How many permanent and portable traffic counting sites should a given State have?
At a minimum, a State should have 6 permanent sites for each grouping of functional classified roadway. For detailed information, please visit the Traffic Monitoring Guide at http://www.fhwa.dot.gov/ohim/tmguide/index.htm and the Highway Performance Monitoring System (HPMS) Appendix C and K at http://www.fhwa.dot.gov/ohim/hpmsmanl/hpms.cfm. For definitions of roadway functional classification, Please visit http://www.fhwa.dot.gov/planning/fctoc.htm.
- How is TVT done each month?
The Traffic Volume Trends (TVT) report is published monthly by the Federal Highway Administration (FHWA). The report estimates the vehicle miles traveled (VMT) by state and several functional classes of roads. The estimates are based on two sources of data:
- The Highway Performance Monitoring System (HPMS), and
- Monthly traffic counts from automatic traffic recorders (ATRs).
The HPMS compiles data from the states annually concerning the condition and performance of all roads in the United States. HPMS includes the annual average daily traffic (AADT) by road segment. When these AADTs are multiplied by the length of each road segment and summed for all road segments and days of the year, they yield the annual VMT.
The states submit to FHWA traffic counts from their ATRs each month. These ATRs are permanent traffic counting devices such as inductive loops in the roadway. There are about 4000 ATRs that are reported to FHWA each month.
ATR data are submitted and processed using the Travel Monitoring Analysis System (TMAS). The FHWA runs quality control checks on all data received. Only data passing the checks are used for the TVT report.
Monthly average daily traffic (MADT) is computed from the ATR traffic counts. Each MADT is compared with the MADT for the same month the previous year to yield a change rate. The change rates are averaged by functional class of road. If a state does not provide traffic data in time, their change rates are estimated from the surrounding states.
TVT estimates monthly VMT by combining the change rates for each month with the most recent annual VMT from HPMS. The TVT report is available to the public within 60 days after the close of the month. Data that covers a minimum of 30 states and 70% of the VMT is required for publication. The next month's TVT report will include an update which covers more data.
The December TVT provides the first estimate of annual VMT for performance measures such as crash rates. When the annual HPMS data are available, they will supersede the total VMT from TVT.
- What are seasonally-adjusted vehicle miles traveled (VMT)?
Seasonally adjusted VMT are monthly VMT adjusted to eliminate day of week, weekday and weekend, and holiday effects. Monthly shifts in data as well as short and long-term trends can be best seen through seasonally-adjusted data.
- How can I use the seasonally-adjusted VMT data?
Seasonally-adjusted VMT data enables comparisons with any other month in any other year. Analysis of seasonally-adjusted VMT is an alternative to analysis of unadjusted VMT, which traditionally uses comparisons of a month to the same month in previous years to determine trends. Seasonally adjusted VMT data enables not only same monthly travel pattern comparisons from different years, but comparisons with any other month.
- What is the process used to gain the seasonally-adjusted VMT?
Seasonal adjustment is a process of estimating and removing movement in a time series caused by regular seasonal variations in activity, e.g. an increase in VMT during summer months or when a major holiday like Thanksgiving occurs at the end of a month with travel spilling-over into December. The Bureau of Transportation Statistics uses Census X12-ARIMA Seasonal Adjustment Program to seasonally adjust VMT. For more information on seasonal adjustment, please visit the Bureau of Transportation Statistics weblink at http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/subject-areas/economics_and_finance/deseasonalized_data
