jats:p Changes in travel behavior near the Sheppard Subway Line in Toronto, Ontario, Canada, and the associated greenhouse gas impacts were examined. A study looked at initial changes in mode share after the line opened in 2002 and examined ongoing mode share trends through 2012. The initial mode shift was assessed through an analysis of bus boardings, subway platform counts, and traffic counts made between 2000 and 2012. Longitudinal changes in mode share were assessed with the use of transit survey data. For the first 6 years of operation, the Sheppard Subway Line produced more greenhouse gas (GHG) per passenger kilometer traveled (PKT) than the bus that it had replaced. A net GHG reduction of 66.4 kilotons of COjats:sub2</jats:sub> equivalent was calculated but was wholly dependent on avoided car PKTs that may have been offset in their entirety by induced travel on Sheppard Avenue. </jats:p>