How important is transportation to the economy? The U.S. Department of Transportation hopes that a new economic index that tracks the movement of freight and passengers will provide important insight into the overall economy's health.

The new indicator, called the Transportation Services Index, will focus on the movement of freight and passenger traffic by land, water and air. The DOT says it expects the TSI to become an important economic benchmark—much like the employment index or consumer confidence index.

The TSI will use monthly data on freight movement and passenger travel in the for-hire transportation sector, weighted and seasonally adjusted by DOT analysts. The freight measures in the TSI will cover for-hire trucking and parcel services, freight railroad services (including intermodal shipments), inland waterway traffic, pipeline movements and air freight. The passenger transportation measures will be drawn from local transit, intercity passenger rail and air passenger transportation data. The first TSI numbers were to be released this month.