The Bay Area's rapid population growth and urban expansion in the early 20th century produced several problems in transportation and water supply. Encroachment of seawater into the North Bay and the San Joaquin Delta was a cause for concern, while the ever-increasing volume of automobile traffic challenged the capacities of the new bridges. The various bold schemes and grandiose designs for solving these problems may raise eyebrows today and, indeed, were controversial in their own time. Consensus proved elusive and the projects were not put into effect. Meanwhile, the development of the Bay Area Rapid Transit (BART) system provided transbay commuters with an alternative to bridges and the great age of bridge building on the Bay came (at least temporarily) to an end.