The main problem with parkways in the Boston area is that the DCR refuses to put any kind of bike accommodation on the roadway, and squeezes as many lanes of traffic on them as they can. If they eliminated some general lanes and put in some bike lanes, it would slow the traffic and make them much more pleasant. The DCR's position has typically been that bikes should be accommodated off the roadway, which is fine for some people, but you can't make all the connections you need that way, nor do all bicyclists want to ride on the paths all the time.