Publication Number: FHWA-SA-96-012
Date: January 1996

Traffic Data Now Available from LTPP Database

The National Information Management System (NIMS) managed under FHWA's long-term pavement performance (LTPP) studies now includes actual traffic data collected at monitored general pavement studies (GPS) sites. The data have been collected by State and provincial highway departments since 1990, but accessibility to the data was delayed until standardized processing procedures could be developed. Until now, the only traffic information available from NIMS consisted of historical estimates based on truck weight and volume information collected from roadways similar to the GPS sites.

The newly available traffic data covers the 1990-1993 period and contains information on

• traffic and truck volumes,
• weight distributions of axle groups by vehicle type, and
• equivalent single-axle load estimates.

The information is based on vehicle counts collected at more than 470 GPS sites and vehicle weights measured at nearly 400 GPS sites in 48 States and provinces. The raw data are stored in the Central Traffic Database (CTDB), which includes hourly vehicle counts, individual vehicle weight records, daily vehicle totals,and axle group distributions. The information is then evaluated, filtered, and summarized for inclusion in NIMS.

LTPP data are available as ASCII, Microsoft Excel, or SAS files furnished on 90-mm (3.5-inch) diskettes, QIC-80 tapes, or hard-copy printouts.

For more information or to obtain a copy of the data request form, contact Barbara Ostrom at FHWA.

New Address for LTPP Data Requests

Until recently, the National Information Management System (NIMS) and the Central Traffic Database (CTDB) were housed and maintained at the Transportation Research Board (TRB), which was also responsible for responding to data requests. TRB's responsibilities are shifting to more of an oversight role, and FHWA has assumed responsibility for the daily operation of NIMS and CTDB.

To request data from NIMS or CTDB, complete the LTPP data request form included in FHWA's LTPP Data Sampler and Data Request Program (see April 1995 Focus) and submit it to:

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