During the past 10 years the U.S. Department of Transportation has spent $3.9 billion on bicycle and pedestrian facilities through the Transportation Enhancements Program. These funds have been distributed to 11,456 projects. Of these funds $2.53 billion has been spent on off-road trails, for 6,537 projects. Many of these projects have been built, and the question of the degree to which these trails are being used for transportation can be asked. The term transportation trip means that a person riding a bicycle on a trail is headed for a destination, such as work, shopping, or school. To explore the question, a geographic information system-based analysis using the block-group level of journey-to-work data from the 2000 census was performed on 13 trails in urban areas. The research explores the overall bike-to-work rate for households in the county in which the trail is located and compares that rate with that of the subset of households that are within 0.5 mi of the trail. The hypothesis that households closer to the trail would have a greater bike-to-work rate is supported by the data in 9 of the 13 analyzed trails. For those 9 trails, households within 0.5 mi of the trail show an average bike-to-work rate of 1.55% as compared with the average of the whole county of 0.52% and a national average of 0.4%. Additionally, fully 25% of bike commuters in those counties live within 0.5 mi of the trail. Factors that influence bicycle commute rates on trails are also reviewed.