 Wayne D. Cottrell of the University of Utah conducted a critical review of PRT academic literature since the 1960s.He concluded that there are several issues that would benefit from more research, including urban integration, risks of PRT investment, bad publicity, technical problems, and competing interests from other transport modes.He suggests that these issues, "while not unsolvable, are formidable," and that the literature might be improved by better introspection and criticism of PRT.