"Nobody goes there anymore, it's too crowded."
the Minuteman Commuter Bikeway between Bedford and Cambridge, MA is, despite the name, a really good MUP. There are stretches where there are lots of pedestrians and you have to slow down, but there are also long segments where you can ride in the mid-20s without any problems. And if you go early in the morning, there won't be much in the way of any traffic. You really can't expect any more than that in a thickly settled urban area.