sentences:  US 281 travels through small towns and sparsely-populated areas, alternating between a divided highway and a main street and passing through a Border Patrol checkpoint south of Falfurrias, until joining I-37 north of Three Rivers.The two routes split south of Pleasanton and separately travel northward to San Antonio.In San Antonio, US 281 overlaps I-410 on the south side of the city until another interchange with I-37.