If two vehicles collide due to one vehicle running a red light, what should be indicated on the CR-3?

When documenting a collision in which one vehicle has run a red light, the CR-3 should indicate "Signal Violation." This classification captures the essence of the event—one driver failed to adhere to the traffic signal, which directly contributed to the accident.

By marking it as a signal violation, the report emphasizes the responsibility of the driver who disregarded the established traffic control device. It highlights the nature of the infraction that led to the collision, serving as a critical piece of information for law enforcement and insurance purposes. This designation helps in determining fault in the accident and potentially influences legal outcomes and traffic safety analyses in the future.

The other options, while relevant in different contexts, do not accurately reflect the primary cause of the incident. For example, stopping distance pertains to vehicle operation under normal circumstances, mechanical failure relates to issues with a vehicle's functioning rather than a traffic law violation, and driver error is a broader category that encompasses various mistakes beyond just running a red light.