Lower income people walk or bike if the density and layout of a neighborhood or district makes that possible. In the case of higher income folks--not so much.  These are the conclusions of a University of Washington (UW) research project based on responses to random surveys of two income groups--one between $40,000 and $60,000 per year and the other above $140,000--in several Seattle area neighborhoods. The higher income people tend to walk or bike only if they find their neighborhood attractive and do so for more discretionary or recreational trips. A summary of the research effort led by Xi Zhu, who graduated with a master's degree in civil and environmental engineering from the UW in 2015, is available here.