[AStonesThrow]

Rail-based transit also provides major side-benefits to its routes: development and improvement.

The principle is that bus routes can change, bus stops can move. Rail right-of-way and train stations are quite permanent and immobile.

Therefore, if a city invests in rail, the developers will follow, and redevelop, revitalize, or gentrify neighborhoods along that route. Conversely, folks in the neighborhood may fight the rail expansion, because "there goes the neighborhood" usually in a more upscale fashion.

It was smart for cities to build out streetcar lines in their early expansions, enticing developers into areas that promised long-term access. Of course, rail lines don't last forever, but the point is being more permanent and staying put, more reliably, than rubber-tire-based transit.