Trying to find a relationship between "quality of life" and light rail transit development, one must first define the term "quality of life" in respect to transit. The Economist's Quality-of-life Index measures Health, Family Life, Community Life, Material Well-being, Political Stability, Climate, Job Security, Political Freedom, and Gender Equality, most of which are not aspects that one would expect to be affected by the advent of a light rail transit system.
Instead, for my uses, "quality of life" is more importantly determined by more definitively "transit-oriented" factors. Factors such as affected mobility, real estate values, change in transit times, and attracting development. These factors, given quantitative value, can be entered into a "quality of life" matrix, which, factoring in the relative values of each, could give one a "quality of life" score for several different light rail systems, along with comparative bus transit systems, and freeway-only systems.