Recent decades have seen an explosion of interest in cycling, both street-type and off-road type. A common term for these facilities is simply "bike trail". These trails may be built to a different set of standards than foot trails, requiring more stable, harder surfaces, less strenuous grades, longer sight visibility, and less sharp changes in direction. On the other hand, the cross-slope of a bike trail may be significantly greater than a foot trail, and the actual treadway may be narrower in some cases.