This practice will permit various agencies to compare intersection turning movement data using two foundational principles, truth in data and base data integrity. These two principles help ensure that intersection turning movement counts can be correctly interpreted and appropriately used to improve the safe and efficient operation of intersections. The principles may be summarized as follows:

Truth in data principle-The truth in data principle provides information that assists potential data users to understand what the data do and do not mean. The opportunity to collect data that advise safe and efficient transportation carries with it the obligation to report how the data were collected, edited, summarized, and reported.

Base data integrity principle-The principle of base data integrity retains the field data collected. In keeping with the principle of base data integrity, it is possible to look at the original data to verify any subsequent changes to the data. In intersection turning movement and other data collection activities, field data may be edited, adjusted, and then summarized and reported. Whatever steps are taken to ensure the quality of the data summarized, the base data must not be corrupted. In keeping with the principle of truth in data, editing and adjustments are documented.