Hey Tulip - I heard that they were having a problem w/a jerk or jerks putting tacks down on the trail near National Airport again. Apparently, someone over there hates cyclists and these carpet tacks flatten tires on a regular basis. Just a word to the wise if you use that part of the trail on your way to Old Town. Apparently, the park service have a special magnetized machine that they roll along the trail to get rid of the tacks.