However, the recent integration of campus and community has not been without problems. For one thing, an urban university can generate major traffic and exacerbate parking problems in adjacent neighbourhoods. The quality of neighbourhoods near a university may deteriorate. Certain industries requiring highly educated workers, such as biotechnology, may be drawn to college communities. The growth of these knowledge economies, and additional upwardly mobile residents, may increase the competition for community space or drive up land costs. The expansion of campuses has led to the razing of some neighbourhoods and the displacement of large numbers of city residents. These factors create continuing tensions between town and gown, but in some scenarios, the university and the local community work together in revitalisation projects.