What is the required accuracy for speedometers in vehicles?

The required accuracy for speedometers in vehicles is defined by regulations that ensure drivers receive reliable information about their speed. A speedometer must be accurate within a specific percentage of the actual speed, typically set at 10% above the actual speed to account for tolerances in manufacturing and to promote safety. Since 90% accuracy means that the speedometer can read anywhere from 90% to 110% of the actual speed, this provides a reasonable margin that ensures drivers are aware of their speed relative to the speed limit, thereby enhancing road safety.

When a speedometer maintains this level of accuracy, it significantly reduces the risk of speeding violations and improves overall roadway safety by helping drivers remain aware of their speed. This standard is important for both regulatory compliance and safe driving practices, making the 90% accuracy requirement a key factor in vehicle design and manufacturing.