University of California Institute of Transportation Studies

Limited-access freeways physically divide urban neighborhoods, creating “severance” or “barrier effects.” In these cases, streets that would otherwise be continuous dead-end at a freeway. Unless the freeway is elevated or in a tunnel, crossings are limited to dedicated bridges or underpasses, often creating lengthy detours for pedestrians and cyclists and making walking and cycling less feasible for many trips. Previous research shows that high school students in Davis, California, are less likely to bicycle if they have to cross the freeway, partly because the available routes are indirect. Pedestrians and cyclists may find their access to transit impeded by freeways as well. Even at freeway crossings that do exist, physical severance can be exacerbated by poor or missing sidewalks, lighting, or bicycle lanes, and by fast-moving traffic entering or exiting the freeway. In the case of pedestrian bridges over the freeway, steps or circuitous ramps may hinder mobility as well.