Massachusetts's primary keep-right rule is found in Massachusetts General Laws Chapter 89, §4B.
On Massachusetts roadways, a driver generally must use the lane nearest the right side of the roadway when that lane is available for ordinary travel.
A driver may use another lane when overtaking and passing another vehicle or when preparing for a lawful left turn.
If the right lane has been constructed or designated for a purpose other than ordinary travel, drivers generally must use the lane immediately adjacent to it instead, unless signs specifically permit use of that right lane.
Massachusetts passing law also requires a driver overtaking another vehicle to pass at a safe distance on the left and not return to the right until safely clear. The driver being overtaken must generally give way to the right and may not unnecessarily obstruct the passing vehicle.
Heavy commercial vehicles are subject to an additional rule on highways with more than one passing lane in the same direction. Those vehicles generally must use the right-hand travel lane and may use only the next adjacent lane when overtaking and passing, except in an emergency.
Exceptions
- Overtaking and passing another vehicle traveling in the same direction.
- Preparing for a lawful left turn.
- Using the lane adjacent to the right lane when the right lane is designated for a purpose other than ordinary travel.
- Following signs that specifically permit use of an otherwise restricted right lane.
- Following the direction of a police officer.
- Highway construction, repair or maintenance conditions that require departure from normal lane use.
Penalties
A violation of Massachusetts General Laws Chapter 89, §§1 through 4C, including the keep-right rule in §4B, may result in a forfeiture of up to $100 unless another penalty specifically applies.
The same maximum applies to improperly using a right lane that has been designated for a purpose other than ordinary travel under §4B.
Official Source
Massachusetts General Laws Chapter 89, §§4B and 4C - Keep Right and Heavy Vehicle Lane Rules
Last verified: October 11, 2026