Often several parties at once. The driver may be liable for negligence; the trucking company is generally responsible when the driver was working, and may have its own liability for negligent hiring, training, scheduling pressure, or maintenance failures. Cargo loading companies can be responsible for improperly secured loads, and maintenance contractors for mechanical failures.

Each party usually has a different insurer, which is why truck claims are far more complex than ordinary car accidents — and why a prompt, thorough investigation matters so much.