The main issue you will confront if you get into a dispute with police over bicycle prohibitions is whether the prohibition is supported by law. Often it is not. Example: the ramp from Commonwealth Avenue to Route 128 northbound and Norumbega Road in Weston. The No Bicycles etc. sign is placed at its entrance (well, actually slightly past the entrance so you don’t see it till too late) but also too early because it applies only to the entrance to Route 128. Note the limitations expressed in CMR 9.08 and MGL 85 11B — limited-access or express state highway where signs have been posted. If there is no sign where you entered, you shouldn’t be cited. I recall years ago having an official document listing what actually are state highways — they are all numbered highways, but actually only a few of them. If you went to the State House Library or inquired of MassDOT, you could get that info.
700 CMR 7.02 and 7.06 establish that bicycles are not permitted on specific Ways that are part of state highways:
Way is defined as the Turnpike, the Metropolitan Highway System, tunnels, a service or rest area, that is located on property owned or controlled and under the jurisdiction of the Department, and includes the areas appurtenant to said way that are necessary for the operation, construction and maintenance of the way
(4) Prohibited Entry to or Use of a Way. The Department prohibits the following vehicles from entering or using a way:
(d) Propelled by Muscle Power. A vehicle propelled by muscle power, including without limitation a bicycle or a vehicle drawn by a horse or other animal, or a motorized bicycle or moped
