Section 4A. When any way has been divided into lanes, the driver of a vehicle shall so drive that the vehicle shall be entirely within a single lane, and he shall not move from the lane in which he is driving until he has first ascertained if such movement can be made with safety. The operators of motorcycles shall not ride abreast of more than one other motorcycle, shall ride single file when passing, and shall not pass any other motor vehicle within the same lane, except another motorcycle.
Structure Massachusetts General Laws
Part I - Administration of the Government
Title XIV - Public Ways and Works
Section 2 - Passing Vehicle Traveling in Same Direction
Section 3 - Sleigh or Sled; Bells
Section 4 - Keeping to Right While View Obstructed
Section 4a - Driving Vehicles in a Single Lane; Motorcycles, Riding and Passing
Section 4b - Driving in Lane Nearest Right Side of Way
Section 4c - Heavy Trucks; Driving in Right-Hand Lane on Multi-Lane Highways
Section 4d - Standing or Parking of Motor Vehicle in a Designated Bike Lane
Section 5 - Penalty; Exceptions
Section 6 - Applicability of Rules of Road to Street Railway Cars
Section 6a - Stopping of Street Railway Cars for Passage of Fire Apparatus
Section 7 - Right of Way of Fire Engines, Patrol Vehicles and Ambulances; Obstruction; Penalties
Section 7a - Restrictions on Use of Ways Upon Approach of Emergency Vehicles
Section 7b - Operation of Emergency Vehicles
Section 7d - Moving of Vehicle Involved in a Crash From a Travel Lane
Section 8 - Right-of-Way at Intersecting Ways; Turning on Red Signals
Section 9 - Designation of Highways as Through Ways; Traffic Control Signs and Devices
Section 10 - Violation of One-Way Traffic; Civil Liability
Section 11 - Marked Crosswalks; Yielding Right of Way to Pedestrians; Penalty