Rail transit is rapid transit. Rail is high-capacity transit. Only the most heavily used heavy rail trunk lines have greater capacity than busways, and these have significantly higher costs. Rail will decongest roads by converting automobile drivers into mass transit riders. Support for rail voiced by drivers is based on a hope that others will use rail transit and open up the road, and in fact rail riders are taken out of buses, not cars.
Rail transit is cost-effective.
Rail is economically inferior to conventional bus service. Rail promotes superior urban form. In any event, rail cannot overcome the forces pushing for decentralization. Rail transit benefits low-income people. Rail construction provides jobs.