The rules work like a lookup table, not a verdict on who drove worse
The rules live in Regulation 668 under Ontario’s Insurance Act, and anyone can read them free on the province’s e-Laws site. They are short and mechanical. Each section describes a situation, such as two vehicles in the same lane or one turning left across another, and states each driver’s share. Many sections come with small drawings of cars and arrows, which is where the word diagrams comes from.
Your adjuster’s job is to pick the section that matches the facts on file. Nobody weighs whose driving was more careless in general, and nobody gives credit for being polite at the scene. If the facts fit a section, the share printed in it is the answer.
That share then drives three things you will feel: whether your deductible applies, how much of the repair runs under direct compensation and how much under your collision coverage, and whether the crash is rated against you at renewal.
Black ice on the Don Valley Parkway does not change your share
The section people find hardest to accept says fault is decided without reference to the circumstances: weather, road conditions, visibility and the actions of pedestrians are all set aside. A February freeze on the DVP, a white-out squall on the 401 near Kennedy, low sun on Sheppard at rush hour, or a pedestrian stepping out at Don Mills, none of it moves the percentage.
So a driver who slid into the car ahead on a sheet of ice is treated the same as one who was looking at a phone. That feels harsh, and it is deliberate. The rules are built to be applied quickly and identically across thousands of claims, which means excluding the arguments that would make every file a debate.
Rear-ends, lane changes and left turns each have a usual reading in the rules
The outcomes below are the usual readings of the relevant sections. The exact wording turns on details, such as whether a vehicle was stopped, moving forward, or in the middle of a manoeuvre, so treat these as orientation rather than a ruling on your file.
- Rear-end in the same lane: the car in front was stopped or moving forward, and the driver who hit it from behind usually carries all of the fault.
- Chain reactions in stop-and-go traffic: the rules have their own diagrams, and the middle car’s share depends on whether it struck the car ahead before or after being pushed.
- Lane change: the driver moving into an occupied lane usually takes all of it; two drivers moving into the same lane at once are usually split evenly.
- Left turn across oncoming traffic: the turning driver usually carries the fault, unless the oncoming car entered against a red light.
- Leaving a driveway, plaza exit or parking lot onto the road: the vehicle entering the roadway usually carries the fault for hitting traffic already on it.
When no diagram fits, the adjuster has to leave the table
Plenty of crashes do not match any section neatly: a three-way tangle in a mall exit, a reversing truck at a loading dock, two cars meeting head-on in a narrow condo ramp. The regulation itself says that where an incident is not described in any section, fault is determined under the ordinary rules of law. That is a negligence analysis, and it can land anywhere, including on a 50/50 split.
More often the trouble is not a missing diagram but the wrong one. The adjuster can only choose from the facts reported. If the file says you were changing lanes when you were holding your lane at the 404 merge at Highway 7, the lane-change section gets applied and you take the fault. The point of impact on each car is one of the strongest clues to which section is right: a rear-bumper hit is hard to square with a lane-change story, while a scrape along a front door fits one easily.
Your percentage shows up twice: on the repair invoice and at renewal
On the repair, the share splits one approved estimate into two payments from your own insurance company. The part you were not responsible for is paid under direct compensation, often with no deductible. The part you were responsible for runs under your collision coverage, with the collision deductible generally scaled to match. A driver who dropped collision coverage on an older car pays that slice personally, which is why a 25 percent finding can still sting.
At renewal, any share above zero can be recorded as an at-fault accident, and how much it moves the premium is the insurance company’s own rating decision. The two effects are linked but separate. Paying your share of a repair out of pocket does not undo a finding that has already been made on a reported crash.
Asking for the decision to be looked at again starts with one question
Ask in writing which section of the rules was applied and what facts it was based on. Then open Regulation 668, find that section, and read the drawing against what happened. A review request is strongest when it shows that a different section describes the crash, backed by something checkable: dashcam footage, an independent witness, the police or Collision Reporting Centre report, or dated photos of where the cars came to rest.
If the adjuster keeps the decision, the route continues to a claims supervisor, then the company’s complaints officer, and after that the General Insurance OmbudService. Our part is narrow. We do not decide fault or argue it, but the damage photos we take for the estimate record the height, direction and spread of the impact, and you are welcome to send them with your request.
Questions people ask
Where can I read the Fault Determination Rules for myself?
On Ontario’s e-Laws site, under Regulation 668 made under the Insurance Act. The sections are short, and the diagrams make them easier to follow than most legislation. Reading the one your adjuster cites takes a few minutes and tells you whether the facts on file match it.
I braked hard for an animal and got rear-ended on Don Mills Road. Am I partly at fault?
Usually not. The rear-end sections look at the positions and movement of the cars, not at the reason the front car slowed. The following driver typically carries the whole share. That can change if the facts put you in a different section, such as having just cut into that lane.
Does a ticket issued at the scene decide which section applies?
Not directly. A Highway Traffic Act charge and a fault finding are separate processes. The ticket is useful evidence of what happened, and you should send it in, but the adjuster still picks the section from the facts of the crash itself.
Do the rules still apply if police never came and nobody went to a reporting centre?
Yes. The rules apply to the facts the insurance company has, however they were gathered. Without a report, though, those facts come down to two drivers’ statements and the damage, which makes your own photos and any witness far more important.