@gemini The D, after all, is the lightest of light rail and goes further than your proposal. Now if you were proposing overlaying rail service along 128... that would absolutely be heavy rail. And also something we should do because JFC get the cars off that damn road. :)
(We also should extend the red on either end to hit the ring line, and the green D to do the same, and run more cars just from 128 in along the pike to North or South station...)