Loop detectors, car-mounted transponders and ultra-fast finish-line cameras combine to call every close finish and support every officiating decision. NASCAR’s Cup Series now decides race finishes by the slimmest of margins – often just thousandths of a second. For example, at Atlanta Motor Speedway in early 2024, Daniel Suarez crossed the line just 0.003 seconds ahead of Ryan Blaney.
To judge outcomes that close, NASCAR deploys a suite of timing-and-scoring technology. Every stock car carries two electronic transponders (one on each side of the rear chassis) and dozens of wire loops are buried in the asphalt around the track. These loops pick up the transponder signals as cars pass. As veteran crew chief Larry Mac explained, “Nobody uses stopwatches anymore. Everything is electronically scored. There are timing loops in the racetrack… the most important one at the start-finish line.”
Each transponder is mounted at a fixed distance from the nose so that when the car’s front crosses the laser timing plane, the loop registers the precise moment. This hardware gives officials a continuous feed of timing data as cars complete each lap.
Loop data graphics from NASCAR’s timing system illustrate how every track is wired with embedded timing loops that capture each car’s pass. The system introduced “loop data” in 2005 to track lap-by-lap positions from the myriad loops around a speedway. In practice, NASCAR calls the live telemetry from all these loops “loop data.”
Each racing surface typically has 15–18 loops at key locations. When a car’s transponder passes over a loop, a timestamp is recorded and fed instantly to Race Control. By stitching together all loop hits, NASCAR can reconstruct every driver’s spot on track for each lap. Officials use that data not only to update the running order but also to adjudicate cautions and wave-arounds in real time. In short, the loops are the backbone of NASCAR’s scoring – giving live split-times and position data to the timing crew.
At the finish line, NASCAR layers in high-speed cameras for final verification. The start-finish detection plane is precisely aligned with the painted stripe on the track, and two line-scan cameras (one mounted slightly higher as a backup) are trained on that line. These cameras (by Lynx/FinishLynx) operate constantly, capturing vertical pixel strips any time a car moves past the line. In racing conditions they typically run about 6,000–8,000 frames per second (the hardware can go up to 20,000 fps).
The moment a car’s front splitter breaks the plane, the camera is triggered and records thousands of timestamped “slices” of the finish line in real time. Those slices are then composited into a single photo-finish image showing each car’s nose as it crossed the line. A red overlay marks the exact start/finish plane. That composite image is delivered immediately to NASCAR’s scoring officials. An operator in Race Control (or a truck in the broadcast compound) can pull up the photo and verify the order at the line.
In fact, race-control personnel routinely refer to results “per the camera” when finishes are tight. For example, in the 2024 Kansas race the timing loops originally showed Chris Buescher fractionally ahead (within the transponder tolerance) – but the photo-finish image made it clear Kyle Larson was nose-first by 0.001 seconds. NASCAR noted that the raw timing data put Buescher ahead by 1.5 milliseconds (the system’s error margin), but the image overrode it to award Larson the win. In every case of a dead-heat on the timing lines, that FinishLynx camera image becomes the definitive record.
Behind the scenes, NASCAR’s Race Control team watches all of this data unfold. Dozens of live timing feeds from the loops flow into the tower computers, showing the running order, lap counts and pit stops for every car. Officials like scoring director Kyle McKinney and veteran director David Hoots monitor the screens on multiple workstations. The loop data is used throughout the race to sort out cautions and penalties.
For instance, when a caution flies, the system instantly identifies the first lapped car (the “free pass”) and the field order. As David Hoots explains, the sensors “confirm the free passes… wave-around; they’re basically the backup, looking at the scoring data to what we’re seeing.” In other words, the electronics provide an automated second opinion on every racing situation, so officials don’t have to rely on hand-written scorecards or stopwatches.
For 2025, NASCAR is adding another layer of precision: GPS tracking. Effective with Speedweeks, each Cup car must carry a NASCAR-provided GPS antenna in the right rear window as part of the new Incident Data Acquisition System. This move fulfills NASCAR’s long-stated plan “to go from loop data to GPS,” eliminating any timing blind spots between loops.
The GPS unit will stream continuous position and speed data back to NASCAR (and only NASCAR) on each car. Teams will no longer need to guess about off-line timing – officials will know exactly where every car is on the track at all times. It’s a technology step aimed at avoiding any controversy; as one NASCAR memo put it, the goal is “improved transparency: a detailed view of on-track incidents” for clear, data-driven rulings (and NASCAR retains sole ownership of the data).
In practice this web of technology has produced rock-solid results in 2025. Through the first races of the year, every finish has been called cleanly by the computers and cameras — and teams have the evidence to back it up. Pit-road exit cameras (linked to the same system) even help confirm lap counters and caution laps when cars peel off.
Commentators note that at the end of each stage or race, officials simply say “per the camera” and show the photo finish image to fans, leaving little doubt. The impact is tangible: there have been no disputed winning passes or mis-scored restarts where technology had to be second-guessed.
As McKinney emphasizes, “Precision is vital for all facets of our sport, and NASCAR timing and scoring is as precise as it’s ever been.” NASCAR’s timing-and-scoring system may be hidden from view under the paint and pavement, but its effect is obvious. It lets the right car take victory lane every time, even when the difference is less than an eyelash.
By uniting loop-based electronics, transponder data and 20,000-fps cameras — soon supplemented by live GPS feeds — NASCAR has assured competitors and fans that finishes are settled by science, not speculation. In short, today’s photo-finish is unambiguous: the hardware and software do the math, and officials enforce it down to the thousandth of a second.
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