Fault in a Massachusetts crash is rarely all or nothing. If an adjuster says the wreck was partly your doing, your claim is not over. It becomes a math problem, set by one statute: M.G.L. c. 231, section 85.1 Massachusetts uses modified comparative negligence, so sharing some of the blame lowers what you can collect without automatically wiping out your case.
The stakes are common. Massachusetts recorded 128,769 crashes statewide in 2025,2 and Boston alone logged 451 in April 2026.3 Most of those claims involve at least some argument over who did what: who had the green, who was following too closely. How that argument resolves decides how much money changes hands.
The 51 percent bar
The rule has a hard edge. You can recover as long as your share of the fault is "not greater than the total amount of negligence" of the people you are suing.1 Carry 50 percent of the blame or less and you still recover. Cross to 51 percent and you collect nothing. A tie goes to you: at exactly 50/50 you can still recover, because 50 is not greater than 50.
That structure is the modified version of comparative negligence. It is more forgiving than the old contributory-negligence rule, which once barred any plaintiff who was even slightly at fault, and stricter than the pure comparative approach some states use, where a driver 90 percent at fault still collects 10 percent. Massachusetts draws its line at 50 percent.
When you do recover, the award drops by your percentage. Section 85 says damages "shall be diminished in proportion to the amount of negligence attributable" to you.1 Value a case at $100,000 and assign you 30 percent of the fault, and you take home $70,000. Push your share to 60 percent and you take home nothing, even if the other driver was also careless.
Who has to prove you were careless
The insurer cannot simply announce that you share the blame and let it stick. Under section 85, "the burden of alleging and proving" your negligence rests on the party trying to establish it.1 That is the defense, not you. Comparative fault is something the other side has to raise and back up with evidence, not a discount the adjuster gets to assume.
When more than one driver is at fault
Section 85 compares your negligence to "the total negligence of all persons against whom recovery is sought," combined.1 In a three-car pileup you are measured against the other drivers as a group, not one at a time. So if you are 40 percent at fault and two other drivers split the remaining 60 percent, you stay under the 51 percent bar and recover, reduced by your 40 percent.
Among those other drivers, Massachusetts allows contribution. Chapter 231B, section 1 provides that "where two or more persons become jointly liable in tort for the same injury ... there shall be a right of contribution among them," with no tortfeasor forced to pay beyond "his own pro rata share."4 For the injured person, the practical upshot is that you usually do not have to divide the defendants' shares yourself; they reimburse each other after paying you.
Comparative negligence is the second gate
Here is the part that surprises people. Massachusetts is a no-fault state. Before comparative negligence enters the picture at all, your own Personal Injury Protection (PIP) coverage pays the first $8,000 of medical bills and related losses regardless of who caused the crash.5
To step outside no-fault and sue the other driver for pain and suffering, you first have to clear the tort threshold in M.G.L. c. 231, section 6D: more than $2,000 in reasonable and necessary medical expenses, or an injury that "causes death," "consists of a fracture," involves "loss of a body member" or "permanent and serious disfigurement," or causes loss of sight or hearing.6 So the section 6D threshold comes first, and only once you are through that door does the section 85 fault comparison decide how much you keep.
How the percentage actually gets assigned
No one stamps a fault percentage on a crash at the scene. It comes from evidence, and both sides build it. The officer's narrative and diagram, the physical damage on each vehicle, any citations issued, and witness statements all feed the number an adjuster or jury settles on. Because the point of impact and a repair estimate can support or sink a fault theory, the details in your Massachusetts crash report and any diminished value claim can matter well beyond the repair bill.
Weather is not an excuse
Massachusetts winters are real. Boston averages roughly 49 inches of snow a year.7 Snow and ice do not lower the standard of care; drivers are expected to slow down and leave more room when the roads turn bad. Insurers use that expectation in reverse, arguing that a driver who lost control on a slick road was going too fast for conditions and so owns part of the fault. Since even a modest percentage assigned to you shrinks the payout, winter crashes are a frequent place for comparative-fault fights.
Deadlines and thin coverage raise the stakes
You have three years from the date of the crash to file a personal injury lawsuit in Massachusetts, under M.G.L. c. 260, section 2A, and the same three-year clock covers property damage.8 Insurers start shaping the comparative-fault story long before that, often on the first recorded call, so what you say in the days after a crash can echo through the claim for years.
Coverage limits sharpen the problem. Massachusetts minimum liability coverage rose to 25/50/30, meaning $25,000 per person and $50,000 per accident for bodily injury plus $30,000 for property damage, for policies issued or renewed on or after July 1, 2025.9 Uninsured motorist coverage must be carried at those same bodily injury limits.10 If a jury trims your award for comparative fault and the at-fault driver carries only the minimum, a large percentage reduction can leave you well short of your actual losses. That is a real reason the fault split is worth contesting rather than accepting.
If your crash involves shared blame, thin policy limits, or an injury serious enough to clear the section 6D threshold, the percentage someone hangs on you can decide whether you are made whole. You can start by finding a Massachusetts attorney through the legal directory.
This article is general information, not legal advice.
Sources
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Mass. Gen. Laws ch. 231, § 85 (comparative negligence). https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleII/Chapter231/Section85
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thatcarhitme.com, Massachusetts Year-over-Year Crash Report, 2025. https://thatcarhitme.com/crash-data/massachusetts/statewide/2025-annual-report
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thatcarhitme.com, Boston, MA Crash Report, April 2026. https://thatcarhitme.com/crash-data/massachusetts/boston/april-2026-report
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Mass. Gen. Laws ch. 231B, § 1 (contribution among joint tortfeasors). https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleII/Chapter231B/Section1
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Mass. Gen. Laws ch. 90, § 34M (Personal Injury Protection). https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXIV/Chapter90/Section34M
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Mass. Gen. Laws ch. 231, § 6D (tort threshold for pain and suffering). https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleII/Chapter231/Section6D
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National Weather Service, Boston/Norton MA climatological normals (1991-2020). https://forecast.weather.gov/product.php?site=NWS&product=CLM&issuedby=BOS
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Mass. Gen. Laws ch. 260, § 2A (three-year statute of limitations). https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleV/Chapter260/Section2A
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Acts of 2024, ch. 275 (amending Mass. Gen. Laws ch. 90, § 34A; minimum coverage effective July 1, 2025). https://malegislature.gov/Laws/SessionLaws/Acts/2024/Chapter275
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Mass. Gen. Laws ch. 175, § 113L (uninsured motorist coverage). https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXXII/Chapter175/Section113L