On campus, walking is affected by safety concerns at intersections, when pedestrians must cross roadways used by motor traffic and bicycles, or walk along improperly built or maintained corridors. Comfort is a characteristic that can encourage more walking. Examples range from protection from the weather and good illumination, to visual appearance and amenities (litter containers, benches, etc.). Despite the Americans with disabilities act (ADA) of 1990, which requires transportation systems to offer equal access to disabled people, the disabled still have problems with stairs, narrow passageways, long distances, slippery surfaces and poor-illuminated areas. The need to provide parking lots in close proximity to buildings also contributes to unfriendly land use development and long walking distance between locations, which can increase the fear of assault, especially after dark or when there are few others around.