How does race timing work?

Without Timing Chips

Non-chip timing systems can very from simplistic to elegant.

At the simplest level, you're local village's race might be run with a stopwatch and a clipboard. A timer starts the watch when someone says "go" and reads a time off of it each time someone crosses the finish line. This works great for a few well-spaced runners, but once there are more than a few, or more than a couple finishing at the same time, it gets difficult.

More sophisticated non-chip timing uses a "time recorder" at the finish line. A button is pressed each time a runners crosses the finish and the exact time for each finish position is recorded. In other words, a time is recorded for first place, second place... One hundredth place... etc. But names still must be associated with each position.

Recording of finishing order is done in several ways. Most often, finishers are routed to a "chute" where they are kept in the same order in which they crossed the finish line. (In such cases it's bad race etiquette, and cheating, to pass someone in the chute!) The finish order is then recorded by simply noting numbers on a clipboard or by removing a tear-off slip from each bib. Another method involves handing each racer a number "stick" as they cross the line and runners later report their stick number.

Once the finishing order is known, it's combined with the finish position times to yield the aggregate results.

With Timing Chips

Timing chips are used in many races to simplify finish line logistics and to provide more accurate timing.

Chips are usually attached in one of two ways - either they are furnished with a Velcro band that is strapped around the ankle or they are fastened into a shoelace. Either way, the chip must be close enough to the ground to interact with the timing "mats" that the runners cross. The mats are really two way antennas that both emit a signal that stimulates a transceiver in the chip and receive the returned serial code from the chip.

Usually, chips are distributed along with number bibs at "packet pickup". The chips are collected at the finish line and you may not be able to exit the finish corral until you've turned your chip in. If your chip is not turned in at the end of the race, you may be billed for it's replacement. If you've picked up your chip and you decide not to run the race, you'll want to make sure the chip gets returned to avoid this charge.

Some races, particularly those using a timing system based on the Champion Chip, also allow runners to use their own chips by registering the serial code of their chips when they register for the race.

All races that use timing chips have at least one timing mat at the finish line. Some races also have a mat at the start line that allows for a true differential time for each runner from the time they individually cross this start line until they cross the finish line. This is often referred to as "chip time". By contrast "gun time" is recorded from the time the starting gun fires with no credit for the time it takes a runner to reach the starting line. The USATF mandates that race results are based on gun time to avoid the situation where a potential race winner could be beaten by a competitor they didn't even see.

Not all races use mats at the starting line and thus provide only "gun times". The two main reasons for this are that the timing companies, those who supply timing equipment for a race, 1) charge additional fees for the start mats and b) have limited supplies of the mats available.

Some larger races also have mats at intermediate locations on the course that can be used to 1) insure runners have completed all sections of the course 2) differentiate runners between races - for example a 5k and a 10k that have common start and end points or 3) provide intermediate "split" times for instantaneous or later updates.

Here is a nice article on timing chips.