What is the primary purpose of a breathalyzer?

The primary purpose of a breathalyzer is to measure a driver's blood alcohol content (BAC). This device is specifically designed to estimate the amount of alcohol in a person's breath, which is then used to calculate the BAC. The BAC is an important metric for law enforcement as it helps determine whether a driver is over the legal limit for alcohol consumption. Understanding a driver's BAC is crucial in enforcing DUI (Driving Under the Influence) laws and ensuring road safety.

In contrast, the other options relate to different aspects entirely. Checking tire pressure is related to vehicle maintenance and safety rather than driver impairment. Assessing vehicle engine temperature pertains to mechanical operation and performance, and evaluating road conditions focuses on the environment where driving occurs. None of these options address the specific function of a breathalyzer, which is central to its use in traffic law enforcement.