Fault determination rules: How Ontario insurers decide who’s at fault in car crashes

Assigning fault after a car crash can be done under Ontario's fault determination rules. These rules decide who pays and by how much, using standardized accident diagrams rather than whoever points the fingers first or shouts the loudest. This article discusses the fault determination rules and how they can help lawyers, clients, and insurers who find themselves in the middle of a crash.

What are Ontario's fault determination rules?

The Fault Determination Rules (FDR) are a set of regulations enacted under Ontario's Insurance Act, which define who is responsible in case of a car accident. These Rules are important, because:

• the FDR help determine who is ultimately at fault for motor vehicle accidents and how that liability is allocated between drivers and insurers
• the FDR require insurance companies to match the accident's facts and degree of fault to one of the scenarios set out in the rules
• the Insurance Act allows injured persons to contest the determination made by the insurance company using the FDR

Here's an example of how the FDR applies in a case, using the scenarios shown in the rules:

We'll discuss these rules in more detail below. You can also bookmark our Personal Injury practice area page for more news and updates for legal professionals in Ontario.

What are the scenarios under Ontario's fault determination rules?

Below are some of the common scenarios in the FDR, with a simplified look at who is at fault, by what percentage, and who is not liable.

Rear‑end or side collisions

Whether one vehicle is parked or both are moving, rear-end or side collisions are common vehicular accidents. Here's how the fault determination rules treat these collisions:

If both cars are travelling in the same direction and in the same lane

• With car A in front and car B behind, car A is not at fault and car B is 100% at fault in any of these situations:
  • car A is stopped or is in forward motion
  • car A is turning to the right or to the left to enter either a side road, private road, or driveway
  • car A is in forward motion and is entering a parking space either on the right or left side of the road
• When car A collides with car B while car B is entering a road from a parking place, private road, or driveway, car B is 100% at fault in the following cases:
  • car B is leaving a parking and car A is passing the parking area
  • there are no traffic signs, and car B is entering a road from a private road or a driveway, while car A is passing the same road or driveway
  • car A collides with car B on a controlled access road, while car B is entering the road from an entrance lane

Here's a video that shows rear-end collisions where car B is 100% at fault:

Head over to our News page, which posts articles that can help Ontario lawyers be up to date with the latest in the provincial legal scene.

Sideswipes

Another common accident covered by the fault determination rules is the sideswipe. Here are the key rules when it comes to sideswipes:

If the two vehicles are traveling in the same direction and in adjacent lanes

• if car B is changing lanes: car A is not at fault, and car B is 100% at fault
• if car A is turning left at an intersection, and car B is overtaking car A: car A is 25% at fault, while car B is 75% at fault
• if car A is turning left at a private road or a driveway, and:
• if car B is overtaking car A: each car is 50% at fault
• if car B is passing one or more automobiles stopped behind car A: car A is not at fault, while car B is 100% at fault

If the two cars are travelling in opposite directions and in adjacent lanes

In all instances, car A is not at fault, while car B is 100% at fault:

• if car B is over the road's center line
• if car B moves left into the path of car A
• if car B is leaving a parking, or is entering the road from a private road or driveway, and car A is overtaking another car

Common rules in sideswipes

Each car is 50% at fault in these two situations, whether the cars are travelling in the same direction and in adjacent lanes or opposite directions and in adjacent lanes:

• if neither vehicle changes lanes, and both cars are on, or over, the center line when the sideswipe occurs
• if the location of the cars is undetermined at the time of the accident

Chain reactions and pile-ups

A chain reaction or a pile-up may happen when three or more cars are involved in a collision. Here's what the fault determination rules say if three or more cars are travelling in the same direction and in the same lane, with car A in front, car B in the middle, and car C at the back:

• if all cars are in motion:
  • the collision between cars A and B: A is not at fault, while B is 50% at fault
  • the collision between cars B and C: B is not at fault, while C is 100% at fault
• if only car C is in motion:
  • the collision between cars A and B: both A and B are not at fault
  • the collision between cars B and C: B is not at fault, while C is 100% at fault

In a pile-up, each car is 50% at fault under the fault determination rules.

Crashes at intersections

Accidents that occur at intersections are divided into two broad categories in the fault determination rules:

If the intersection does not have traffic signs

• if car A enters the intersection before car B: car A is not at fault, and car B is 100% at fault
• if both cars enter the intersection at the same time: if car A is to the right of car B in the intersection, car A is not at fault, while car B is still 100% at fault
• if cannot be determined which car entered the intersection first: each car is 50% at fault

If the intersection has traffic signs

• at a traffic sign:
  • if car B fails to obey a traffic sign: car A is not at fault, and car B is 100% at fault
  • if both cars fail to obey a traffic sign, or it is undetermined who failed to obey a traffic sign: each car is 50% at fault
  • if traffic signals are inoperative: the rules applicable for an all-way stop intersection shall apply
• at an all-way stop intersection:
  • if car A arrives first and stops: car A is still not at fault, while car B is 100% at fault
  • if both cars arrive at the same time and stop: when this occurs and car A is to the right of car B, car A is not at fault and car B is 100% at fault
  • if it cannot be determined which car arrived first: each car is 50% at fault

Parking lot crashes

Motor vehicle accidents also frequently happen in parking lots, mostly due to the limited visibility of drivers, especially when getting in or out of these parking spaces. In these situations, the fault determination rules provide for the following scenarios:

• when two cars are driving in the same direction and in the same lane:
  • car B at the back is 100% at fault, if car A at the front is in forward motion, and is entering a parking on either the right or the left side of the road
  • if car B is entering a road from a parking place, car B is 100% at fault where it leaves a parking space and car A is passing the same parking area
• if car A is leaving a feeder lane or a parking space and fails to yield the right of way to car B on a thoroughfare: car A is 100% at fault, while car B is not

In addition, the fault determination rules state that the same rules for parking lot crashes apply when an accident occurs in a thoroughfare, treating it as a road.

What happens when Ontario's fault determination rules do not apply?

The fault determination rules are limited to the above-listed scenarios. However, if a particular car accident does not fit any of those scenarios, the rules provide a fallback. It states that the degree of fault of the insured shall be determined in accordance with the ordinary rules of law if:

• an incident is not described in any of the scenarios
• there is insufficient information to determine the insured's degree of fault
• one of the cars is charged with a driving offence, and the other car is wholly or partly at fault under the FDR

When two rules may be applied

The fault determination rules also address situations where two or more rules could apply:

• if one or more rules apply: the rule that attributes the least degree of fault to the insured shall be applied
• if two rules apply and one makes the insured is 100% at fault, but the other rule says that the insured is not at fault: the insured shall be deemed to be 50% at fault

Fault determination rules: A guide when cars and claims collide

After a collision, clients often arrive with a stack of letters, a diagram, and a strong sense of unfairness. Clear advice using Ontario's fault determination rules can calm that reaction and turn that confusion into a plan. These rules also help explain how the insurer reached its view, and how that view can be challenged or used to the client's advantage. Using these rules gives lawyers a structured way to test who should pay, and in what proportion.

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