Most American cities were laid out by someone with a plan. Boston was laid out by accumulation, and the road network still reflects a period when the shoreline was somewhere else entirely and the routes were determined by what was already there.

The result is a driving environment that produces a specific category of collision. Not the high-speed interstate crash, but the low-to-moderate-speed impact in a geometry where two drivers each had a defensible reason to believe they had the right of way.

Those are the crashes where fault gets argued, and Massachusetts has a legal structure that makes the argument matter more than people expect.

The Rotary Problem Is a Rules Problem

Rotaries survive around Boston in numbers that surprise visitors, and they are a reliable generator of disputed liability.

The yield rule is clear and widely ignored

Massachusetts law directs any operator entering a rotary to yield the right of way to a vehicle already in the intersection, unless directed otherwise by an officer or a traffic device. Stated that way it sounds unambiguous.

In practice, rotaries around Boston vary in size, lane count, signage quality and sightlines. A multi-lane rotary where an entering driver and a circulating driver collide in the outer lane produces two plausible accounts, and physical damage patterns often support both.

Lane discipline is the hidden variable

The circulating driver’s own conduct comes into play. A driver in the inner lane exiting across the outer lane is doing something the geometry does not really permit, which shifts the analysis substantially.

Storrow Drive Is a Different Failure Mode

Storrow is a parkway built to a 1950s standard carrying modern volumes, and its problems are structural rather than behavioral.

Short merges and no shoulder

Entrances and exits arrive with very little warning and minimal merge distance. There is often nowhere to go when something slows suddenly, which produces chain rear-end collisions where the middle vehicles are struck from both directions.

The clearance signs exist for a reason

The low overpasses are famous enough to have generated their own verb locally. Box trucks and rental moving vans strike them regularly, and the resulting sudden stops and debris cause secondary collisions involving drivers who did nothing wrong at all.

Sorting a chain collision

In a multi-vehicle rear-end sequence, the order of impacts determines everything and is rarely obvious from the damage. This is the scenario where independent evidence matters most and is least likely to be gathered.

Massachusetts Delays the Fault Question

Here is the structural piece that makes Boston crash disputes behave differently from those in most states.

No-fault pays first

Massachusetts requires Personal Injury Protection coverage, which pays medical expenses and some lost wages up to $8,000 per person regardless of who caused the crash. Because the first round of bills gets handled without a fault determination, drivers frequently assume fault has been resolved or does not matter.

It has not been, and it does.

The threshold decides whether fault ever gets litigated

To claim pain and suffering after a motor vehicle crash, a plaintiff generally must exceed a statutory threshold: more than $2,000 in reasonable medical expenses, or an injury causing death, loss of a body member, permanent and serious disfigurement, or loss of sight or hearing.

Why Percentages Get Fought Over

When a case does proceed, Massachusetts divides responsibility rather than assigning it wholesale.

Modified comparative negligence

Under the comparative negligence statute, contributory negligence does not bar recovery as long as the claimant’s negligence is not greater than the total negligence of the parties they are claiming against. Damages are then reduced in proportion to the claimant’s own share.

The practical effect is a hard edge. At 50 percent, a claim survives and pays half. Above that it pays nothing. In an ambiguous rotary collision, the entire dispute can compress into the difference between 49 and 51.

This is why insurers ask what they ask

Early questions about speed, familiarity with the route, phone use and whether you saw the other vehicle are not idle. Each answer moves a percentage in a negotiation that has not been announced as one.

According to Matthew A. Rabin, Partner and Managing Attorney at RTRLAW, disputed-geometry collisions are decided less by the police narrative than by physical evidence of approach angle and impact sequence, because those are the facts that survive cross-examination when both drivers genuinely believe they had the right of way. Drivers facing a contested fault finding frequently consult a Boston counsel for auto accident victims before giving a recorded statement, since the percentage assigned early tends to anchor everything afterward.

What Actually Helps at a Boston Crash Scene

Photograph the final rest positions before anything moves, because in a rotary or a chain collision the geometry is the case. Capture the signage and lane markings from a driver’s approach view, which establishes what you could actually see.

Get a police report even for a minor impact, and note the responding department, since a rotary can sit on the boundary between jurisdictions. Identify witnesses immediately, because traffic disperses fast on Storrow and nobody stops.

And avoid narrating fault at the scene. In a geometry that confuses everyone, a generous word at the curb becomes a fixed percentage three months later.