What lights can be switched on when parked under poor environmental conditions?

When parked under poor environmental conditions, such as heavy fog, rain, or snow, it is important to be visible to other drivers to prevent accidents. Rear fog lights are specifically designed to make the rear of a vehicle more visible to those behind it in conditions of reduced visibility. These lights emit a bright red light that stands out during adverse weather, alerting other drivers to the presence of a stationary vehicle.

While other lighting options might seem suitable for increasing visibility, they serve different purposes. Sidelights are generally used when a vehicle is parked on a road at night, but they are not particularly effective in poor conditions because they do not provide significant illumination for others to see the vehicle from a distance. Hazard warning lights alert other drivers to a potential hazard, indicating the vehicle is stationary, but they are not intended specifically for visibility in foggy conditions. Headlights are typically used for driving and would not be appropriate for a parked vehicle as they can be too bright and could cause glare for other drivers. Hence, in this context, using rear fog lights is the most effective way to ensure safety when parked under adverse weather conditions.