What is one reason you might need to notify the police after a crash?

Notifying the police after a crash is particularly important if your vehicle is unattended. This situation can often lead to further complications, such as the potential for your vehicle being damaged or creating a hazard to other road users. When a car accident occurs and the vehicle is left without supervision, it becomes necessary to alert the authorities. The police can manage the situation effectively, ensuring that proper procedures are followed to secure the scene and prevent additional accidents. They can also help document the incident, which can be crucial for insurance purposes and any subsequent claims or investigations.

Other scenarios presented may have their own significance, but they don’t hold the same critical urgency. For example, filing a complaint against another driver typically falls under civil matters rather than immediate police intervention. Similarly, gathering statements from witnesses can be handled after the police arrive and assess the situation, rather than being a standalone reason for contacting them. Notifying the police about traffic conditions might also be relevant, but it's not as direct a necessity as dealing with an unattended vehicle following a crash.