Massachusetts Traffic Laws and Rules of the Road
Right-of-way and intersections
Massachusetts uses first-to-stop, first-to-go at four-way stops; if two vehicles arrive together, the driver on the left yields. At uncontrolled intersections, yield to the vehicle on your right. Left-turning traffic yields to oncoming through traffic. In a roundabout, entering traffic yields to traffic already circulating. A school bus with red lights flashing requires a stop from both directions unless a divided highway separates you.
Speed and turning
Default limits are 30 mph in thickly settled or business districts, 40 mph on other roads, and 50 mph on divided highways unless posted otherwise; school zones drop to 20 mph when posted and children are present. Right on red after a full stop is legal unless signed otherwise, and Massachusetts also permits a left on red from a one-way onto a one-way unless posted.
Protecting others
Pass cyclists with at least 3 feet of clearance. The Move Over Law requires slowing and shifting away from stopped emergency, tow, and maintenance vehicles. Seat belts are required for all occupants, and children under 8 and under 57 inches need a child seat or booster. Handheld phone use is prohibited for all drivers; junior operators may not use any phone, hands-free included.
Traps and rule of thumb
Questions love the exceptions: right on red is default-permitted, not default-prohibited; the rear-seat belt mandate attaches to passengers under 13; and a flashing yellow school-bus signal does not require a stop. Rule of thumb: if the limit is not posted and you can see buildings, driveways, and pedestrians, treat it as 30 mph.