The Chicago "L" is the rapid transit system serving the city of Chicago and some of its surrounding suburbs in the U

l train elevated transit rapid transit system chicago aerial cta metra subway elevated perspective cityscape commuter railway metropolitan chill weather urbanite movement vapor trails crisp atmosphere seasonal frost skyscrapers public transport downtown infrastructure highrise structures rooftops glass facades rail tracks street grid congested roads pedestrian activity ventilation plumes cold climate concrete jungle commuting flow city living industrial steam locomotion building clusters traffic arteries office towers residential blocks energy consumption environmental dynamics vehicle congestion structural design urban transit metropolitan hub climate response thoroughfares heating systems midday urbanity towering edifices