CityLab, the Atlantic's blog about urban issues, has a nice set of visualizations about income along fixed-route transit lines inspired by The New Yorker's New York City Subway Project. Portland is one of the cities featured and here is a look at the line that represents perhaps the most income inequality - mostly because of the Washington Park stop that 'serves' the West Hills (ave. income $146,779) shortly after serving the Old Town neighborhood (ave. income $18,540).
Go there and click on the others for comparison as well as comparing across Atlanta, Chicago and Washington, DC.
Wonder how the installation of fixed-route transit affects gentrification of the neighborhoods served? Well here is another CityLab article looking at a study that argues that gentrification is a small causal effect.