What is a standard reference point typically used by most drivers?

A side mirror serves as a standard reference point for drivers because it provides essential visibility for monitoring adjacent traffic, which is crucial for safe navigation on the road. By using the side mirror, drivers can effectively judge distances and adjust their positioning relative to other vehicles, helping them make informed decisions when merging, changing lanes, or parking. This reference point allows for a better awareness of the surrounding environment, contributing to overall road safety.

The other options are not standard reference points in the same context. A measuring tape is typically used for precise measurements and is not practical for real-time driving situations. A speedometer is crucial for monitoring speed but does not assist in spatial awareness of nearby vehicles. Headlight position can indicate alignment and visibility but does not provide the same level of situational awareness as the side mirror does when driving.