What is the purpose of a USATF certified course?
The purpose of the USATF course certification program is to produce road race courses of accurately measured distances. For any road running performance to be accepted as a record or be nationally ranked, it must be run on a USATF-certified course. In addition, the certification program is very important to the average road racer, as well as those of exceptional speed. Most runners like to compare performances run on different courses, and such comparisons are difficult if course distances are not reliable. No one can truly establish a personal best if the course distance is not accurate.
How are courses certified?
A race course is defined by the shortest possible route that a runner could take and not be disqualified. A given runner might not follow the shortest possible route, but the actual path of any given runner is irrelevant. The shortest possible route is a reasonably well-defined and unambiguous route that ensures all runners will run at least the stated race distance.
You might envision the shortest possible route as a string, stretched tightly along the course so that it comes within 30 cm (one foot) of all corners, straight through S-turns, and diagonally between corners when crossing a street. Courses are measured following the same route as that hypothetical string.
When making a turn, measurements are made prudently close to the curb or edge of the roadway. Often manholes, storm drains, broken pavement and other hazards render this impractical. In such cases, measurements are of the shortest route that a runner may be expected to take.