The railroad was highly successful, carrying commuters into Boston and the Boston urban population to the seaside resorts. By 1914 over seven million passengers were carried annually, making it one of the most heavily traveled stretches of railroad in North America. With such a traffic density, the expense of electrification could be easily recouped. By 1928, all existing cars were fitted with electric motors, trolley poles, and control stands and the steam locomotives were disposed of. However, the number of riders decreased during the Great Depression and completion of the Sumner Tunnel between East Boston and downtown Boston in 1934 allowed automobiles to compete with the ferries.