Ontario Fault Determination Rules

ontario fault deteremination rules

The Ontario Fault Determination Rules are legislated in regulation R.R.O, Reg 668 of the Insurance Act of Ontario.   Car insurance companies in Ontario use the Fault Determination Rules to assign fault to drivers in motor vehicle accidents.  The FDR rules depict various accident scenarios and set out regulations for apportioning liability. Auto claims in Ontario are settled according to these rules.  

How do insurance companies determine who is at fault for a car accident?

Insurance companies use the Fault Determination Rules to determine who’s at fault in an accident.  The FDR rules depict common accident scenarios from which the claims adjuster references to designate fault or liability to the driver and vehicle. As mentioned previously, the fault is expressed as a ratio, between 0% and 100% for both at-fault and not-at-fault accidents. 

The type of auto insurance coverage applied to your auto claim depends on the fault determination assigned by your adjuster.  For example, if you are deemed 100% at fault for an accident, optional loss coverage such as collision or all perils coverage would be used to cover your claim.  If you were 100% not at fault, your DCPD, or Direct Compensation Property Damage coverage would be used instead of Collision or All Perils.

What happens if I disagree with the fault determination rule?

If you disagree with the fault determination that your insurance company has designated for your accident, you can always dispute the decision. The Ontario Insurance Act stipulates a dispute resolution when you and the insurance company cannot agree on fault or liability.  The dispute resolution clause states that if you’re not satisfied with the degree of fault assigned to you by your insurance company, or the fault designation does not accurately reflect the circumstances around your accident, you can sue your insurance company! The courts will then review the details of the accident by the ordinary rules of law (tort law).    

section 263 of insurance act of ontario fault dispute resolution

Ontario Fault Determination Rules Chart

The fault determination chart is a series of common, accident scenarios, where liability or fault is expressed as a percentage for each vehicle. 

Rear-end collision Fault 

There are three rear-end collision scenarios in the Ontario Fault Determination Rules:

All vehicles are driving in the same lane and direction. 

  1. the vehicle rear-ended was stopped or in forward motion  
Rear End Collision – Fault Determination Rules Ontario – 6 (2)
  1. the vehicle rear-ended was turning left or right into a private road, driveway or side road.
Rear End Collision – Fault Determination Rules Ontario 6 (3)
  1. The vehicle rear-ended was in forward motion and entering a parking place on either the right or left side of the road
Rear End Collision – Fault Determination Rules Ontario 6 (4)

In all three rear-end accident scenarios the vehicle that was rear-ended is 100% not at fault.  

Who is at fault in a rear-end collision involving 3 cars?

A collision involving three vehicles travelling in the same direction and the same lane is called a chain reaction collision.  There are two different fault determinations for chain reaction accidents.

1. If vehicles A, B, and C are in forward motion when the accident occurs, vehicle A is 0% at fault; vehicle B is 50% at fault, and vehicle C is 100% at fault for the accident.  In the collision between Vehicle B and C, the driver of Vehicle B is not at fault and the driver of Vehicle C is 100% at fault. 

Chain Reaction Car Accident – Fault Determination Rules – Ontario – 9 (1-3)

2. If only vehicle C was in motion, vehicles B and A are not at fault and vehicle C is 100% at fault for the accident. 

Chain Reaction – Fault Determination Rules – Ontario – 9 (4)

Is the middle car at fault in a three-car accident? 

In a three-vehicle chain collision, the middle vehicle can either be at fault or not.  This depends on whether the middle vehicle was in motion or not. If the middle vehicle was in motion the fault determination would be 50% at fault. If the middle vehicle was completely stopped and pushed into the vehicle ahead, the fault would be 0% at fault.

Who is at fault in a rear-end collision involving 3 cars chain collision
When all three vehicles are in motion

OR

three vehicle in motion last vehicle 100% at fault
The first two vehicles stopped when the third vehicle rear-ended vehicle B

Please see FDR rule 9 (1-3)

Who is at fault in a rear-end collision involving four cars?

A four-vehicle rear-end collision is very similar to a three-vehicle car accident. If the two, middle vehicles were in motion they would be 50% at fault each, while the vehicle in front of the chain would be 100% not at fault and the last vehicle 100% at fault for the accident. If all three vehicles were stopped before the last vehicle in the chain, the last vehicle is 100% at fault, while the other three vehicles are not liable.  

Please see FDR rule 9 (1-3)

Ontario Fault Determination Rules for Pileup Accidents

A pileup is when three or more vehicles drive in the same direction and adjacent lanes. For each collision between two vehicles involved in the pile-up, the driver of each vehicle is 50% at fault for the accident. 

Pile Up Car Accident- Fault Determination Rules – Ontario – 11 (1-2)

Ontario Fault Determination Rules for Sideswipe Accidents

A sideswipe happens when vehicles travelling in the same direction and adjacent lanes collide. If the location on the road of the sideswipe cannot be determined each driver is held 50% at fault for the accident. 

Sideswipe – 10 (3) – Fault Determination Rules Ontario

Ontario Fault Determination Rules for Parking Lot Accidents

Section 16 of the Ontario Fault Determination Rules outlines rules for accidents that happen in a parking lot

The main takeaway is that vehicles driving on the main thoroughfare have the right of way over cars driving in the feeder lanes.  Also, vehicles leaving a parking space need to give vehicles in feeder lanes the right of way.  

What happens if more than one FDR rule applies in your accident scenario? 

Section 4 (1) of the Ontario Fault Determination Rules states that the rule which attributes the least degree of fault is the only rule that should be used in that circumstance.

However, section 4 (2) states that if two rules apply where the fault is designated 100% at-fault for one, and 100% Not-at-fault for the other, the insured would be deemed 50% responsible. 

if more than one fault determination rules apply

Ontario Fault Determination Rules for Accidents on Private Property

There is no provision in the Ontario Fault Determination Rules, which specifically addresses accidents which happen on private property.  However, the regulation does have specific rules for accidents in parking lots, which always tend to be on private property.  Also, private roadways are treated like any other roadway, as per the regulation. 

Ontario Fault Determination Rules for Accidents with Cyclists or Pedestrians 

A fault determination rule does not specifically exist for accidents involving a vehicle and a cyclist or pedestrian.  However, section 5 (1) states that if an incident is not described in any of the FDR rules, the incident shall be determined by the ordinary rule of law (tort-baed).  Also, the Ontario Faut Determination is meant for accidents involving two or more automobiles, not pedestrians or cyclists! 

when accident scenario not in the fdr rules ontario

Ontario Fault Determination Rules for Single Vehicle Accidents

The Ontario Fault Determination Rules are designed for adjudicating fault or liability for accidents involving two or more motor vehicles and do not specify single-vehicle accidents.  However, all single-vehicle accidents in Ontario are considered to be 100% at-fault, regardless of the weather conditions or if not charged with an offence by the Police. 

Ontario Fault Determination Rules when Turning Left

There are four, left-turn collision scenarios in the Ontario Fault Determination Rules:

All vehicles are driving in the same direction and adjacent lanes:

  1. Turning left at an intersection.
Turning Left – 10 (5) Fault Determination Rules Ontario
  1. Turning left into a private road or driveway.
Turning Left – Fault Determination Rules Ontario – 10 (6)
  1. Turning left into the path of another vehicle 
Turning Left in Opposite Directions – Fault Determination Rules Ontario
  1. Turning left into a private road or driveway while another vehicle tries to pass on the adjacent lane
Turning Left – Fault Determination Rules Ontario – 10 (7)

In all four left turn accident scenarios, the fault ranges from 0% to 100% liability.

Ontario Fault Determination Rules when Someone is Charged with a Driving Offence 

There is a provision in the Ontario Fault Determination Rules that deals with situations when one or more than one driver gets charged for an offence. 

A driver is considered to be charged with a driving offence if one of the following occurs:

  • Impairment by alcohol or drugs
  • Charged with an indictable offence related to the operation of the vehicle
  • Driver refuses breathalyzer or drug test
  • Speeding 16 kilometres over the speed limit

The degree of fault is set by the ordinary rule of law, and not with the fault determination rules if driver A is charged with a driving offence AND the driver of vehicle B is wholly or partly at fault, as otherwise determined by the FDR rules. 

Lane Change Accident Fault Determination Ontario

There are two, lane change collision scenarios in the Ontario Fault Determination Rules:

All vehicles are driving in the same direction and adjacent lanes:

  1. When neither vehicle changes lanes and one or both vehicles go over the centreline 
Changing Lanes – Fault Determination Rules – Ontario -10 (1-2)
  1. When either vehicle changes lanes
Changing Lanes – Fault Determination Rules – Ontario – 10 (4)

Ontario Fault Determination Rules when Overtaking another Vehicle

Overtaking is depicted in the FDR rules as vehicles travelling in opposite directions and adjacent lanes.  This rule applies when a vehicle is entering a private road or driveway, or leaving a parking space and another vehicle attempts to overtake vehicle C. 

Overtaking – Fault Determination Rules Ontario

Overtaking is depicted in the FDR rules as vehicles travelling in opposite directions and adjacent lanes.  This rule applies when a vehicle is entering a private road or driveway, or leaving a parking space and another vehicle attempts to overtake vehicle C. 

Overtaking – Fault Determination Rules Ontario

Ontario Fault Determination Rules for Merging Lanes

The Ontario FDR rule for merging lanes is based on vehicles that are travelling in the same direction and same lane. The key takeaway is that the vehicle doing the merging is 100% responsible for establishing its laneway, and must always yield to traffic. If two vehicles collide while one vehicle is merging, the vehicle that is merging is 100% At fault. 

Merging Lanes – Fault Determination Rules Ontario

Peter Martire, CIP, CRM, RIBO – Executive Editor and Insurance Advisor

Peter has been working in the insurance industry since 2005. He has over 18 years of experience adjudicating complex auto insurance claims and sales and service brokering. In March of 2024, he partnered with Begin Insurance Inc. as a Senior Insurance Advisor. He also serves as Executive Editor of carinsuranceinontario .ca.

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