Quick answer: The fault determination rules Ontario insurers must follow are a regulation under the Insurance Act. Your insurer uses them to decide how much of a collision was your fault, from 0% to 100%. The rules ignore weather, road conditions and visibility, so sliding on black ice does not reduce your share. If you rear-end a car, change lanes into another vehicle, or back up into someone, you are usually 100% at fault.
Winter is when these rules catch drivers off guard. It’s easy to assume an icy road will count in your favour. It won’t. Below is how the rules work, the scenarios that come up most in winter, and what your fault percentage means for your claim and your premium.
What are the Fault Determination Rules in Ontario?
The Fault Determination Rules are Regulation 668 (R.R.O. 1990) under Ontario’s Insurance Act. The regulation says an insurer “shall determine the degree of fault of its insured” using these rules. They were last amended in 2018.
According to the Financial Services Regulatory Authority of Ontario (FSRA), the rules use diagrams covering “more than 40 accident situations.” Fault can be shared, and each driver can be found anywhere from 0% to 100% at fault. The diagrams are illustrations only. Your insurer matches your collision to the scenario it most closely resembles.
Three general rules shape every decision:
- Conditions don’t count. Fault is decided without regard to weather, road conditions, visibility or the actions of pedestrians (section 3).
- Where the cars touched doesn’t count either. The location of the damage on each vehicle is not used to decide fault (section 3).
- The rule most favourable to you wins. If more than one rule applies, your insurer must use the one that gives you the lowest fault. If one rule makes you 100% at fault and another makes you 0% at fault in a two-car collision, you are deemed 50% at fault (section 4).
Does snow or ice change fault under Ontario’s fault determination rules?
No. Section 3 of the rules says fault is assessed without regard to weather, road conditions or visibility. FSRA’s claims guide repeats this. Fault applies “regardless of road or weather conditions, visibility, point of impact on the vehicles or the actions of pedestrians.”
In practice, the rules treat a winter crash exactly like the same crash on a dry July afternoon. If you couldn’t stop on ice and hit the car ahead, the rear-end rule applies. If you lost traction while changing lanes, the lane-change rule applies. This is why winter tires, extra following distance and slower speeds matter so much in winter. They protect your driving record as well as your car.
Common winter collisions and how fault is usually assigned
| Winter scenario | Rule that usually applies | Typical fault split |
|---|---|---|
| You slide on ice and rear-end a stopped car | Rear-end, section 6 | You 100%, other driver 0% |
| You slide while changing lanes and sideswipe a car | Same direction, adjacent lanes, section 10 | Lane-changer 100% |
| Lane markings are buried in snow and no one can show who left their lane | Section 10 | 50% / 50% |
| Traffic lights are out after an ice storm | Signals treated as an all-way stop, sections 14–15 | First to arrive and stop has priority |
| You back out of a snowy driveway or parking space into a passing car | Backing up, section 19; parking lots, section 16 | Reversing driver usually 100% |
| Someone hits your legally parked car | Parked vehicles, section 17 | Moving driver 100% |
Who is at fault in a rear-end collision under Ontario’s fault determination rules?
The driver behind is 100% at fault, and the car that was hit is 0% at fault. Section 6 applies when both cars are travelling in the same direction and lane, and the lead car is stopped or moving forward. It also applies when the lead car is turning into a side road or driveway, or pulling into a parking spot.
This rule is why the Insurance Bureau of Canada (IBC) warns about the “swoop and squat” staged collision. One car cuts in front of you and brakes hard so that you rear-end it. Under section 6, you would normally carry 100% of the fault. IBC’s advice is simple: “Always keep plenty of distance between you and the car ahead.” On snow and ice, that distance needs to be far greater than usual.
Chain reactions. When three or more cars collide in the same lane, section 9 assesses each collision between two cars separately. If only the last car was moving, that driver is generally 100% at fault for hitting the car ahead.
Who is at fault when changing lanes or sideswiping?
If one driver was changing lanes, that driver is 100% at fault (section 10). If neither car changed lanes and both were on or over the centre line, or if no one can establish where the cars were, fault is split 50/50.
That 50/50 outcome is common in winter, when snow hides lane markings. Photos of the road, the vehicles’ final positions and any dashcam footage can make the difference between 50% and 0%.
Section 10 also covers left turns. If you are turning left at an intersection and a car tries to pass you, the rules usually split fault 25% to you and 75% to the passing driver.
Who is at fault at an intersection under the fault determination rules in Ontario?
It depends on what controls the intersection:
- No signs or signals (section 13): The car that entered first has the right of way. If both entered at the same time, the car on the right has it. If the order can’t be established, fault is split 50/50.
- Stop or yield signs (section 14): A driver who fails to obey the sign is 100% at fault. At an all-way stop, the first car to arrive and stop has priority.
- Traffic signals (section 15): A driver who runs the signal is 100% at fault. If the signals aren’t working, the intersection is treated as an all-way stop.
- Left turns across oncoming traffic (section 12): A driver who turns left into the path of an oncoming car is usually 100% at fault.
Who is at fault in a parking lot collision?
Section 16 treats a parking lot’s main lanes in and out, called thoroughfares, like roads. Smaller lanes between rows are feeder lanes. A driver leaving a feeder lane or a parking space who fails to yield to traffic on a thoroughfare is 100% at fault.
Other rules apply everywhere, including parking lots. Under section 19, a driver who is backing up or making a U-turn is generally 100% at fault. Under section 17, a driver who hits a legally parked car is 100% at fault.
What happens if no rule fits, or someone was charged?
Not every crash fits the fault determination rules Ontario insurers apply. If a collision isn’t described in any rule, or there isn’t enough information to apply one, section 5 says fault is decided under “the ordinary rules of law.” The rules also make an exception when a driver is charged with certain serious offences, such as impaired driving. In those cases, fault can be decided under ordinary law instead.
Don’t assume a police charge settles the question, though. FSRA says that being charged with an offence “does not necessarily mean you will be found at-fault for insurance purposes.” Not being charged doesn’t mean you’re fault-free either.
What does your fault percentage mean for your claim and premium?
Your fault percentage decides two things: what your insurer pays for your car, and whether the collision counts against you at renewal.
Your vehicle damage. Direct Compensation – Property Damage (DC-PD) pays for damage to your car, its contents and loss of use, to the extent you weren’t at fault. FSRA’s example: if you were 75% at fault, your insurer pays 25% of your loss, less any deductible. If the other driver is identified, insured and fully at fault, DC-PD can pay the whole repair when your DC-PD deductible is zero. Since January 2024 you can elect not to claim DC-PD. FSRA cautions that opting out “may not be the best option for you.” For the share that was your fault, you need collision coverage.
Your driving record. FSRA says that if you are found 50% or more at fault, the accident goes on your insurance record and “there is a good chance your premium will go up” at renewal. The same applies if someone you lend your car to is found 50% or more at fault. Our guide to car insurance renewal in Ontario explains how claims history feeds into your renewal rate.
How do you dispute a fault decision in Ontario?
- Ask which rule was applied. Under the fault determination rules Ontario insurers must use, every decision should point to a specific scenario. FSRA tells drivers to ask their claims adjuster which Fault Determination Rule was used. Compare it with what happened.
- Send your evidence. Give the adjuster photos, witness details, dashcam footage and the police or collision reporting centre report.
- Escalate. If the insurer won’t revise its decision, FSRA says to contact your insurer’s complaints officer. Our step-by-step guide to disputing a denied insurance claim in Ontario covers the complaint process and free external review.
The best evidence is gathered at the scene. IBC advises drivers never to admit fault, sign anything about fault, or promise to pay for damage. Record the names, plate numbers and insurance details of every driver, passenger and witness, and photograph the damage. For the full sequence, from calling police to reporting within seven days, see how to file a car insurance claim in Ontario.
How a broker helps after a winter collision
A broker can’t change the Fault Determination Rules, and the insurer makes the fault decision. A broker can check which rule was applied, help you put your evidence in front of the adjuster, and explain how the result affects your renewal.
It also pays to review your coverage before the worst of winter. Check your collision coverage and deductibles against what auto coverage you really need in Ontario. If you’ve installed winter tires, make sure you’re getting the winter tire insurance discount. To talk it through, request a call back from an AAXEL broker, or see our auto insurance page.
Information current as of November 2, 2026.
Frequently asked questions
What are the Fault Determination Rules in Ontario?
They are Regulation 668 under Ontario’s Insurance Act. Insurers must use them to decide how much of a collision each of their insured drivers caused, from 0% to 100%. FSRA says the rules include diagrams for more than 40 accident situations.
Is the driver who rear-ends another car always at fault in Ontario?
Almost always. Under section 6, if the car ahead was stopped or moving forward in the same lane, the driver behind is 100% at fault. This also applies when the car ahead was turning into a driveway or parking spot.
Do the fault determination rules in Ontario change when roads are icy?
No. Section 3 says fault is assessed without regard to weather, road conditions or visibility. A winter crash is assessed the same way as the same crash on a dry road.
Who is at fault when both drivers change lanes at the same time?
If neither driver can be shown to have changed lanes, or no one can establish where the cars were, fault is usually split 50/50 under section 10. If only one driver was changing lanes, that driver is 100% at fault.
How do Ontario’s fault determination rules treat parking lot accidents?
A driver leaving a parking space or a feeder lane who fails to yield to traffic on a main thoroughfare is 100% at fault under section 16. A driver who is backing up is generally 100% at fault under section 19.
Does a police ticket decide who is at fault for insurance?
No. FSRA says being charged with an offence does not necessarily mean you will be found at fault for insurance purposes. Your insurer applies the Fault Determination Rules separately.
How much does being at fault raise my insurance in Ontario?
FSRA doesn’t publish a set percentage. It says that if you are found 50% or more at fault, the accident goes on your record and your premium will likely go up at renewal. The amount depends on your insurer’s approved rating rules.
Can fault be shared in an Ontario car accident?
Yes. FSRA says fault can be shared, and each driver can be found anywhere from 0% to 100% at fault. Common shared outcomes under the rules are 50/50 and 25/75.
Do I pay a deductible if I’m only partly at fault?
FSRA says you can expect to pay your full deductible unless the accident was not your fault or was only partly your fault. DC-PD pays for the share of your loss that wasn’t your fault, less any deductible.
How do I dispute an at-fault decision?
Ask your adjuster which rule was applied and send any evidence that supports a different scenario. If the insurer won’t change its decision, FSRA says to contact the insurer’s complaints officer.
Sources
- Ontario e-Laws: R.R.O. 1990, Reg. 668, Fault Determination Rules: sections 2–6 (insurer duty, conditions ignored, most favourable rule, ordinary rules of law, rear-end) and the rule scenarios referenced above
- FSRA: After an Accident: Understanding the Claims Process: 40+ diagrams, shared fault 0–100%, conditions ignored, police charges, 50% at-fault on your record, lent vehicles, asking which rule applied, complaints officer, DC-PD and deductibles
- FSRA brochure: After an Auto Accident: Understanding the Claims Process: DC-PD example (75% at fault, insurer pays 25%) and zero DC-PD deductible
- FSRA: What is in a standard auto insurance policy?: DC-PD coverage, electing not to claim DC-PD since January 2024, collision coverage
- Insurance Bureau of Canada: Collision Resources: never admit fault, information to record, swoop-and-squat staged collisions
Disclaimer
This article is general information about how Ontario’s Fault Determination Rules work as of November 2, 2026. It is not legal advice. Fault in a specific collision depends on the facts and on how your insurer applies Regulation 668, and coverage depends on your policy and the Ontario Automobile Policy (OAP 1). For advice about your situation, speak to a licensed insurance broker. For an injury claim or lawsuit, consider speaking to a lawyer.
