How ChronoTrack D-Tags Work

Runners in the 2006 Great Gorilla Charity Race take to the streets of London.
Runners in the 2006 Great Gorilla Charity Race take to the streets of London.
Miles Willis/Getty Images

The American psychologist Timothy Leary once observed that, as humans, we continually face the "frightening, terrorizing fact that we do not know who we are, or where we're going in this ocean of chaos."

Obviously, Leary wasn't a running enthusiast.


Because if nothing else, runners often pride themselves on two things: knowing where they're going and knowing exactly how long it took to get there. Maybe that's why they're so fanatical: The race simplifies the entire, freaking human condition.

Ah, but it's not quite that easy. Throw enough competitors out there on the road and even a footrace swells with complexity. Larger marathons can feature runners by the tens of thousands. Imagine even a fraction of them crossing the finish line at the same moment hungry for their best time, and you get a taste of the problem.

Fortunately, humans don't have to face that timing problem on their own. We have fabulous technology to lessen both our logistical and our existential dilemmas. The ChronoTrack D-Tag is one such technology, using ultrahigh frequency (UHF) radio-frequency identification (RFID) to track runners' feet as they race past antennas at key points along the course.

The result? Clarity and certainty about your place in the universe -- or at least 99.84 percent certainty [source: Pique]. And you don't even have to drop acid to get there.

Lacing Up With a D-Tag

Keep your laces on and you're good to go.
Keep your laces on and you're good to go.
Image courtesy ChronoTrack

Radio-frequency identification (RFID) technology is all about the wireless transfer of information via electromagnetic fields. It's not based on visual communication. It doesn't depend on physical contact. A radio transmitter-receiver (also called a reader) sends a signal to the tag and then reads its response. The transmitter-receiver then passes the data to a computer. It's a useful bit of technology that allows us to track livestock, pets, products, baggage and even our fellow human beings.

RFID technology began clocking marathon runners in the 1990s and has since become standard. The race timers simply fit the runners with individualized RFID tags and set up transmitter-receivers at key points along the race. The antennae for these readers typically stand on either side of the track or travel through a padded mat on the surface of the track itself.


Several different companies compete in the race-timing tech market, including Innovative Timing Systems and RFID Race Timing Systems. And then there's ChronoTrack, makers of the D-Tag system -- so named because the tag loops through the runner's shoe laces to form a "D" shape. The tag's position places it in close proximity to the antenna-loaded road mats that runners trample over in the course of the race [source: Impinj].

When a D-tagged runner passes over the mat, the antenna reads the signal and tells the computer who the runner is, where they passed and when they did it. At the end of the race, they can just dump their tags in a wastebin -- or stuff them in that drawer full of sweat-stained marathon keepsakes. Not only does this cut down on post-race hassles for the runners, it also streamlines the whole process for race organizers. If you ever had to stand in line to check a tag after a grueling race, you can appreciate that feature.

Not everyone loves the D-Tag, however. A 99.84 percent efficiency rate for these types of UHF RFID systems is exceptionally high, but it's not perfect -- and certainly not perfect enough for some of the more finicky running enthusiasts. Plus, the whole system depends on laces and shoes. If you prefer running barefoot or in a gorilla costume, then you might have to improvise.

But hey, it's a small price to pay to for a small slice of cosmic certainty.

Author's Note

Amazing, isn't it? The same technology we use to deter shoplifters and tag polar bears can also ensure accurate race recordings. I wonder if we could incorporate these elements into a marathon. Imagine: Runners start out inside a shopping mall and have a 10-second lead on waking polar bears. Next, each runner has to shoplift a single item from a preassigned store and make for the finish line without the polar bear catching him or her. The beautiful part is that, thanks to UHF technology, we'd be able to track every last gory detail.

As long as polar bears eat running shoes, we're good to go.


Related Articles


  • Bookey, Mike. "Timing Through Time." The Pacific Northwest Inlander. May 2, 2012. (June 14, 2012)
  • Guy, Sandra. "How the Chicago Marathon chips track runners." Chicago Sun-Times. Oct. 6, 2011. (June 14, 2012)
  • Impinj. "RFID Case Study: Los Angeles Marathon." (June 22, 2012)
  • Pique, Stephane. "The Truth About RFID Read Rates." RFiD Journal. May 7, 2012. (June 21, 2012)