Seasonal adjustment is the process of estimating and removing movement in a time series caused by regular seasonal variation in activity, e.g., an increase in air travel during summer months. Seasonal movement makes it difficult to see underlying changes in the data. Monthly shifts in data as well as short and long-term trends can be best seen through seasonally-adjusted data.

Seasonally-Adjusted Airline Data

• Airline Traffic Data Press releases
• Seasonally-adjusted data
  • Scheduled Airline
    • Available Seat Miles (Domestic and International)
    • Available Seat Miles (Domestic)
    • Available Seat Miles (International)
    • Enplanements (Domestic and International)
    • Enplanements (Domestic)
    • Enplanements (International)
    • Load Factor (Domestic and International)
    • Load Factor (Domestic)
    • Load Factor (International)
    • Revenue Passenger Miles (Domestic and International)
    • Revenue Passenger Miles (Domestic)
    • Revenue Passenger Miles (International)
  • All Airline Services
    • Revenue Passenger Miles
    • Revenue Ton-Miles
• Source data
  • U.S. Department of Transportation, Bureau of Transportation Statistics (BTS), U.S. Air Carrier Traffic Statistics (unadjusted)

Seasonally-Adjusted Vehicle Miles Traveled

• Seasonally-adjusted data
• Source data
  • U.S. Department of Transportation, Bureau of Transportation Statistics (BTS) calculation from U.S. Department of Transportation, Federal Highway Administration, Traffic Volumes and Trends
  • U.S. Department of Transportation, U.S. Department of Transportation, Federal Highway Administration, Traffic Volumes and Trends (unadjusted)
• Documentation
  • Seasonally Adjusting Vehicle Miles Traveled

Seasonally-Adjusted Modal Data for the Transportation Services Index (TSI)

The monthly data used to create the TSI are highly seasonal. In order to portray real growth in the modal data, BTS uses a method called X12-ARIMA to seasonally-adjust the data.  Whereas the Total, Passenger and Freight TSI indicate the trends of the combined modes, the seasonally-adjusted modal data allow the user to understand which modes are experiencing the changes in trend over time.

Seasonally-adjusted Freight and Passenger TSI Modal Data

• Seasonally-adjusted data
  • Truck tonnage
  • Rail Freight Carloads
  • Rail Freight Intermodal Traffic
  • Rail Passenger Miles
  • Public Transit Ridership
  • Pipeline Movement
  • Natural Gas Consumption
  • U.S. Waterways Tonnage
• Documentation
  • Methodology: Seasonal Adjustment of the Transportation Services Index Time Series Data
  • ARIMA model specifications
• Data Source
  • Transportation Services Index

Documentation

• Seasonally-Adjusted Data: What it Really Means