Complex sentence: Transportation Alternatives is a non-profit organization in New York City which seeks to change New York City's transportation priorities to encourage and increase non-polluting, quiet, city-friendly travel and decrease private car use.
Split into simpler sentences: Transportation Alternatives is a non-profit organization in New York City. T.A. seeks to change New York City's transportation priorities to encourage and increase non-polluting, quiet, city-friendly travel and decrease private car use.