Baltimore City is home to many green spaces, parks, and waterways. Some of the more widely recognized locations include the Inner Harbor, Middle Branch, Druid Hill , Gwynns Falls and Herring Run Parks. City residents in particular value access to green spaces as a place to recreate, exercise and congregate, but the City's green spaces serve a vital role in ensuring clean air and water for long term urban sustainability. Baltimore neighborhoods actively participate in increasing access to green spaces through tree planting and other watershed protection activities such as stream clean-ups. Urban living also enables residents the option to choose alternative means of transportation to reduce vehicle miles traveled by car. The City is already served by numerous modes of mass transit including MARC, metro, light rail, the Charm City Circulator, and bus lines. BNIA-JFI tracks eight indicators to measure the City's urban environment and transit. These indicators are categorized into the following categories: air quality and hazardous waste; tree canopy, alternative transportation mode use; and travel time to work.