Heavy weight of traffic travelling on freeway lanes, outskirts of Washington DC, USA

air pollution american freeway automobiles backviews busy road busy roads carbon emissions carbon footprint city living city outskirts conditions congested congestion district of columbia environmental damage exhaust emissions flowing traffic freeways fumes global warming going away highway highways homeward bound leaving town major routes many vehicles motorway normal traffic overpopulated polluting environment population explosion population growth rush hour rush hour saloon cars traffic flow transport transportation trip vehicles volume of traffic back view cars daytime driving heading home heading off horizontal journey journeys motorways outdoors outside rear view stock image stock photo stock photograph the road ahead the way forward travel travel photo travel photograph travel photography travel stock travels travel destinations travel destination color image color colour tourism destination