How are M-3 cars powered?

Answer: B — Third rail

M-3 cars are powered by the third rail, which is a crucial component of the electric train system used by the Long Island Rail Road and many other commuter rail systems. The third rail runs alongside the tracks and provides a continuous supply of electric power to the trains through a contact shoe that connects with the rail. This system allows for efficient energy transfer, enabling the M-3 cars to operate at relatively high speeds while maintaining a good range of service without the need for onboard fuel sources or complex engine systems found in diesel-powered trains. Utilizing the third rail also helps in minimizing emissions and reducing noise compared to diesel engines, aligning with modern trends towards more environmentally friendly modes of transportation. In contrast, the other options represent different powering systems used in railroads but are not applicable to the M-3 cars specifically. Diesel engines are typically used for freight and some passenger services that do not have electrified tracks. Overhead electric lines are common in light rail systems and certain urban transit systems but are not utilized by M-3 cars. Battery power could theoretically be used in some contexts, but M-3 cars rely on the third rail for their operational power.