When U.S. Secretary of Transportation Norman Mineta rang the bell at the New York Stock Exchange last month, it signaled the beginning of the trading day and the introduction of a new tool for weighing transportation's overall importance to the U.S. economy.

The Feb. 29 event launched the U.S. Department of Transportation's (DOT) Transportation Services Index (TSI). Created by DOT's Bureau of Transportation Statistics, the TSI will measure the movement of freight and passenger traffic by land, water, and air.

Mineta said he expects the index to provide a reliable benchmark of the overall strength of the economy. "Wall Street understands how important numbers are for gauging financial health," he said. "The new Transportation Services Index will fill a crucial void by finally giving us a single number to measure how much transportation means to the American economy."

On the freight side, the new index measures the volumes of for-hire trucking and parcel services, railroad shipments, inland waterway traffic, pipeline movements, and air freight. It will not include international or coastal steamship movements, private trucking, courier services, or the U.S. Postal Service.

The seasonally adjusted index combines data on freight ton-miles and passenger miles traveled, which have been weighted to yield a consistent monthly measure. Although the index is still under development, shippers can expect the first release of TSI figures sometime this month.