From treehugger.com:
Laneway housing is a terrific option to deal with aging boomers and their children.
After years, no, decades of opposition, laneway housing is finally legal in many cities, thanks to the cost of housing and the aging of the baby boomer generation, who are often owners of lovely houses with generous backyards. These new, small laneway houses can become a place for them to downsize, or to provide living space for their kids.