The numbers on a Massachusetts motor vehicle crash report codes grid are not random. Each field on the police report translates one detail of the collision — what was struck, how the vehicles met, what each driver was doing, the road and light conditions, injuries, and restraints — into a numeric code drawn from the state’s Law Enforcement Crash Report Manual. Once you know which field is which, the grid reads as a short, standardized description of the crash.
What follows walks through the coded fields you are most likely to see, in roughly the order they appear on the report.
First Harmful Event
This field identifies the very first thing in the sequence of the crash that caused damage or injury. The most commonly seen entries:
- 1 — Collision with a motor vehicle in transport (another vehicle that was moving or on the roadway)
- 2 — Collision with a parked motor vehicle
- 3 — Collision with a pedestrian
- 4 — Collision with a cyclist
- 5 — Collision with a deer
- 6 — Collision with another animal
- 7 — Collision with a moped
- 8 — Collision with work zone maintenance equipment
The list continues past code 8 to cover fixed objects like trees, utility poles, and guardrails, as well as non-collision events such as rollovers and fires.1Mass Crash Report Manual. First Harmful Event
Each vehicle also gets a separate “Most Harmful Event” code, which identifies the single event that caused the worst damage or injury for that vehicle. When a car hits a guardrail, bounces into another lane, and then collides head-on with a truck, the first harmful event and the most harmful event can be two different numbers.
Manner of Collision
Where the first harmful event tells you what was struck, this field describes how the vehicles met:
- 1 — Single vehicle crash
- 2 — Rear-end
- 3 — Angle (the front of one vehicle hits the side of another)
- 4 — Sideswipe, same direction
- 5 — Sideswipe, opposite direction
- 6 — Head-on
- 7 — Rear to rear (both vehicles were backing up)
Insurance adjusters read this field first because it immediately narrows down what likely happened. A rear-end code almost always places initial fault on the trailing driver. An angle collision at an intersection raises right-of-way questions.2UMassSafe. Massachusetts Law Enforcement Crash Report Manual
Vehicle Action Prior to Crash
This field records what each vehicle was doing in the moments before impact:
- 1 — Travelling straight ahead
- 2 — Slowing or stopped
- 3 — Turning right
- 4 — Turning left
- 5 — Changing lanes
- 6 — Entering a traffic lane (merging from a ramp, pulling away from the shoulder, leaving a curbside parking spot)
- 7 — Leaving a traffic lane
- 8 — Making a U-turn
- 9 — Overtaking or passing
- 10 — Backing
- 11 — Parked
Read side by side with the manner of collision, this field tells most of the story. When one driver is coded “turning left” and the other “travelling straight ahead,” the liability picture takes shape before anyone reads the narrative.3Mass Crash Report Manual. Vehicle Action Prior to Crash
Driver Contributing Code
This is the field where the officer records what the driver did wrong, if anything. For insurance and legal purposes it is arguably the most consequential entry on the report.
- 1 — No improper driving
- 2 — Exceeded authorized speed limit
- 3 — Disregarded traffic signs, signals, or road markings
- 4 — Failed to yield right of way
- 5 — Followed too closely
- 6 — Made an improper turn
- 7 — Driving too fast for conditions
- 8 — Wrong side or wrong way
- 9 — Failure to keep in proper lane or running off road
- 10 — Operating in an erratic, reckless, or aggressive manner
- 11 — Swerving or avoiding due to wind, slippery surface, or an object in the roadway
- 12 — Over-correcting or over-steering
- 13 — Glare
- 14 — Physical impairment
- 15 — Emotional
- 16 — Illness
- 17 — History of heart condition, epilepsy, or fainting
- 18 — Visibility obstructed
- 19 — Inattention
- 20 — Distracted
- 21 — Fatigued or asleep
- 22 — Operating defective equipment
A coding of “no improper driving” versus “failed to yield” can be the difference between an insurer paying your claim and fighting it.4Mass Crash Report Manual. Driver Contributing Code
Alcohol Use and Test Status
Suspected substance involvement is split across two fields. The first captures the officer’s opinion about whether alcohol was present:
- 1 — Yes, alcohol used
- 2 — No, alcohol not used
- 99 — Unknown
The manual states this reflects the officer’s judgment about the presence of alcohol, not a conclusion about how much was consumed.5Mass Crash Report Manual. Suspected Alcohol Use
A separate “Test Status” field records whether a chemical test was actually administered:
- 1 — Test not given
- 2 — Test refused
- 3 — Test given
- 4 — Unknown if tested
When code 3 appears, the officer must also complete the “Type of Test” and “BAC Test Result” fields.6Mass Crash Report Manual. Test Status
Light Conditions
Scene conditions are captured in three independent fields: light, road surface, and weather. They don’t always correlate the way you would expect, which is why each is coded on its own.
- 1 — Daylight
- 2 — Dawn
- 3 — Dusk
- 4 — Dark, lighted roadway
- 5 — Dark, roadway not lighted
- 6 — Dark, unknown roadway lighting
The distinction between codes 4 and 5 can matter for municipal liability questions when a streetlight was out.7Mass Crash Report Manual. Light Conditions
Road Surface
- 1 — Dry
- 2 — Wet
- 3 — Snow
- 4 — Ice (including ice from freezing rain)
- 5 — Sand, mud, dirt, oil, or gravel
- 6 — Standing or moving water (flooding)
- 7 — Slush
A contributing code of “driving too fast for conditions” alongside a road surface code of “ice” tells a fairly complete story on its own.2UMassSafe. Massachusetts Law Enforcement Crash Report Manual
Weather is captured in an additional field covering clear skies, rain, snow, fog, and other atmospheric conditions. A “Road Contributing Circumstances” field separately records hazards like potholes, worn surfaces, or construction zones.
Injury Severity (KABCO)
Every person involved in the crash receives an injury classification on the KABCO scale. Unlike the numeric fields above, these are letter codes used nationally, so they read the same way across state lines:
- K (Fatal) — Any injury resulting in death within 30 days of the crash. If someone initially coded at a lower severity later dies, the code is changed to K.
- A (Incapacitating) — Serious injuries like broken bones, severe lacerations exposing underlying tissue, significant burns, crush injuries, loss of consciousness, or paralysis.
- B (Non-Incapacitating) — Injuries visible at the scene but less severe, such as bruises, minor cuts, or a lump on the head.
- C (Possible) — The person reports pain, nausea, or momentary loss of consciousness, but no wounds are visible.
- O (No Injury) — No reason to believe the person was physically harmed.
The officer makes this call at the scene based on what they can see, which is why the rating doesn’t always match the final medical diagnosis. Traumatic brain injuries, for example, are difficult to detect in the field and are frequently undercoded.8UMassSafe. Massachusetts Law Enforcement Crash Report Data Dictionary If you were coded “O” or “C” at the scene but later received a serious diagnosis, your medical records carry more weight than the police code in any insurance or legal proceeding.
Safety Equipment
Each person gets a code reflecting the restraint or protective equipment in use at impact:
- 0 — None used (no restraint where one was available, or no helmet for a motorcycle rider)
- 1 — Shoulder and lap belt
- 2 — Lap belt only
- 3 — Shoulder belt only
- 4 — Child safety seat
- 5 — Helmet (motorcycle riders only)
- 6 — Helmet (non-motorists like bicyclists or skateboarders)
- 7 — Protective pads (elbows, knees)
- 8 — Reflective clothing
- 9 — Lighting (lights worn or carried by a non-motorist)
Massachusetts follows a modified comparative negligence system, and an insurer can point to a code 0 to argue that the lack of a seatbelt contributed to the severity of the injuries.9Mass Crash Report Manual. Safety System Used
Citation Fields Are Statute Numbers, Not Codes
The report includes up to four citation fields where the officer records traffic violations issued at the scene. These don’t use a separate numbering system; they reference the actual chapter and section of Massachusetts law. If you see entries there, look up the cited statute to see exactly what was charged.
Other Coded Fields
Beyond the major categories above, the form carries dozens of smaller coded entries. The crash-level section captures location (by intersection, address, or mile marker), date, number of vehicles, and whether the crash was school-bus related. Each vehicle entry records make, year, registration, insurance company, and damaged areas. The driver section includes license information, seating position, airbag deployment status, ejection status, and whether the driver was responding to an emergency. Crashes involving trucks or buses add fields for cargo body type, trailer length, gross vehicle weight rating, and whether hazardous materials were released.2UMassSafe. Massachusetts Law Enforcement Crash Report Manual Each of these smaller fields follows the same pattern: a short numbered list in the manual, one of which the officer selects.
If a Code on Your Report Is Wrong
Contact the police department that produced the report and ask to speak with the reporting officer or the records division. If the officer agrees the code is incorrect, they can issue an amended report. Officers generally correct objective errors — a wrong vehicle color, a mismarked road condition — more readily than judgment calls like the driver contributing code.
When the department won’t amend, the Motor Vehicle Crash Operator Report that drivers file under M.G.L. chapter 90, section 26 becomes your own account on the record. It sits alongside the police version in state files.10General Court of Massachusetts. Massachusetts Code Chapter 90 Section 26 – Accident Reports; Supplemental Report; Penalty for Violation If your version contradicts a police code and you have evidence to back it up — photos, witness contact information, dashcam footage — the operator report gives that evidence an official home.
One caveat on the codes generally: insurance adjusters treat the police report as a starting point, not the final word on fault. They compare it against physical evidence, witness statements, surveillance footage, and event data recorder information from the vehicles. A favorable report helps your claim; an unfavorable one doesn’t end it.