Which formula is recognized for determining the horsepower of passenger-carrying vehicles?

The SAE Horsepower Rating Formula is recognized as the standard for determining the horsepower of passenger-carrying vehicles. This formula was established by the Society of Automotive Engineers (SAE) to provide a consistent method for measuring the power output of engines in various vehicles. The formula takes into account several factors, including engine speed and torque, allowing for a reliable assessment of the engine's capacity to perform work.

Using this method ensures that the horsepower ratings are comparable across different vehicles and manufacturers, which is crucial for consumers and regulatory bodies. In contrast, the other options do not specifically pertain to the standardized measurement of horsepower for passenger vehicles as established by the SAE.