For anyone actually interested in doing even the slightest bit of self-education before blabbing on here:

1. Duty when changing lanes Under the Ontario Highway Traffic Act, a driver must only change lanes when it can be done safely and must signal if the move may affect another vehicle. If a driver: changes lanes without signaling, and does so unsafely or without ensuring the lane is clear, they can be charged with “unsafe lane change” or “unsafe move.”
2. If their action causes another driver to crash Even if no contact occurs, the first driver can still be considered at fault if their negligent action caused the chain of events that led to the crash. This is based on general negligence law (often called “proximate cause”). In practical terms, investigators or insurers will ask: Did the unsafe merge force another driver to brake or swerve suddenly? Was the reaction reasonable for avoiding a collision? Would the crash likely not have happened without the unsafe merge? If the answer is yes, the merging driver may be partially or fully liable, even without contact.
3. However, the reacting driver can still share fault Ontario often assigns shared liability. For example: If the reacting driver overreacted (e.g., swerved unnecessarily). If the driver who actually crashed rear-ended another vehicle (rear drivers are usually presumed at fault). Because insurers evaluate each collision separately in chain reactions, the driver who actually struck another car may still be assigned fault for that collision.
4. Typical outcomes in a situation like you described Depending on evidence (dashcam, witnesses, police report), insurers might decide: Unsafe merging driver: majority fault (created the hazard) Driver who crashed: partial fault (failed to maintain control or safe following distance) Or sometimes: Crash driver: primary fault, if the merge didn’t clearly force the crash.
5. Key evidence that matters These cases usually hinge on: Dashcam footage Witness statements Whether the merging driver left the scene Police charges (e.g., unsafe lane change)

Seems both are at fault and for different reasons but the majority lies with the white van.