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How the Chicago Marathon chips track runners

Updated: November 16, 2011 9:25AM

Bank of America Chicago Marathon runners will get instant gratification about their results thanks to a small tag that transmits timing data throughout the course.

Runners affix the tag, called a D-Tag, to their shoelaces. The tags, made by Evansville, Ind.-based ChronoTrack Systems, use Radio Frequency Identification (RFID) technology to transmit location and timing data on each runner.

The RFID tags, each costing about $1, work just like a “smart” chip affixed to a piece of clothing at a retail store that sends its signals to a reader.

Throughout the marathon, the readers that pick up the data are located underneath “timing” mats placed on the course at the start, the half-point, every 3.1 miles and at the finish.

Chicago Marathon runners have affixed timing devices to their shoes since 1998. Technological advances have allowed Chicago to process results faster and more reliably, and the process advanced again last year when the marathon changed tag suppliers.

Now, the readers transmit runners’ data to computer servers, and human timing specialists process the information. This enables marathon officials to update the marathon website in near-real-time with the latest times for each runner, and to compile it so that people who log onto the site can find their favorite runners by name, bib number or by their place within a category such as gender, age, elite runners or wheelchair racers.

The system takes into account how long a runner takes to reach the start line. Some can take 20 minutes or more after the starting gun fires because of the huge crowd.

“A person’s race does not begin until he or she hits the start line,” said Paul Farmer, director of information technology at Chicago Event Management Inc., which runs the marathon. “Before timing technology, no one knew actual start times for runners in large races.”

The system isn’t entirely wireless because the results are too important to leave to the airwaves. So marathon officials use high-speed wire-line or multiple connections at the start, at each checkpoint and at the finish line.

Marathon volunteers at the finish-line area recover the D-Tags so they can be recycled.

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