Ralph Gakenheimer, MIT professor emeritus of urban planning, passed away on June 17 in Concord, Massachusetts. He was 89 years old.A faculty member in the Department of Urban Studies and Planning (DUSP), Gakenheimer focused his research on the dynamic relationship between how we classify and use land with the mobility choices individuals make in cities. He was particularly interested in the intentions and choices behind the selection of a particular mode of mobility and how those choices intersect with sustainability and accessibility in developing nations.During his 40-year tenure at MIT,…