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Commuter rail systems occupy a niche distinct from subways or intercity trains, connecting suburban residents to urban job centers along fixed schedules that peak sharply during morning and evening rush hours. Unlike subways, which run frequently throughout the day, many commuter lines operate with long gaps between trains outside peak times, reflecting lower off-peak demand. This scheduling pattern creates a paradox: infrastructure built to handle enormous rush-hour crowds sits comparatively empty for much of the day, raising questions about cost efficiency. Some transit agencies have responded by extending service frequency into midday hours, hoping to attract non-commuting riders and better justify the fixed costs of track and rolling stock that would otherwise remain underused.