When conducting skid tests to determine friction, how many tests must agree within 10%?

To determine friction through skid tests, the standard practice requires that at least two of the tests produce results that are within 10% of each other. This ensures the reliability and accuracy of the data collected. By having multiple tests that align closely, it reduces the possibility of anomalies influenced by external factors such as surface variations or tire conditions during a single test.

Conducting only one test would not provide enough data for a reliable assessment. Additionally, requiring three or four tests would be unnecessarily stringent for establishing a common range of results when two sufficiently matching tests are already considered adequate within the field. Thus, ensuring that at least two tests agree within the specified percentage is the accepted methodology for collecting sound forensic evidence.