I'm in a bit of a quandary. MGL 90-1b states in part that all moped drivers:

...shall be subject to the traffic laws and regulations of the commonwealth and the regulations contained in this section, except that: (1) the motorized bicycle operator may keep to the right when passing a motor vehicle which is moving in the travel lane of the way...

Critical Mass bicyclists like to block, or "cork," intersections so all the participants can get through, traffic signals be damned. Chan reports on a similar moped ride yesterday:

... about 30 of us on mopeds swarming through the streets of Boston...blocking intersections, blowing through red lights and pedestrian filled crosswalks...for once, as a mass unit, taking over the streets usually very unfriendly to moped riders (although we have every right to be on the street...just as much as cars, trucks, busses and taxicbs)...

You might wonder after reading Heather Parker's complaint about trying (and so far failing) to get some idea where and how she can park her moped:

... i called and spoke to a traffic officer at the police station who said they don't really have an answer and to look it up in the law books. i pleasantly explained that there should be some sort of policy and people knowledgable on this policy - the response i got was i don't give a fuck. i wish i had written down their name. it really wasn't my goal to get anybody angry because i knew it wouldn't benefit anybody, i was simply looking to see if everyone was on the same page and what is acceptable and what is going to earn me a parking violation, or impoundment! ...