Automatic Drive Tracking (ADT)

Automatic Drive Tracking is the umbrella term for an iOS app that detects, records, and classifies a vehicle trip with no user input — the phone notices you started driving, records the route, and ends the trip when you park.

The underlying technology is sensor fusion: combining low-power readings from the accelerometer, gyroscope, magnetometer, and barometer (processed by Apple’s motion coprocessor, integrated into the A-series SoC since the M9 generation) with periodic GPS samples. Apple exposes this stack through the Core Motion framework — specifically CMMotionActivityManager (which classifies activity as automotive, walking, cycling, or stationary) and the location services APIs.

Why this matters for a mileage tracker. Continuous GPS polling drains a battery in hours. The motion coprocessor runs on a dedicated low-power chip and tells the main CPU when to wake up the GPS. The result: a tracker that runs all day, every day, in the background, without killing your phone or your patience. This is the architecture ELM is built on; it is also what underlies Apple Maps’ driving detection and the Health app’s workout auto-start.

A common misconception. “ADT” is a category, not a product. ELM is one implementation; competing trackers use similar approaches. What differs is the trip-classification logic (is this drive business or personal?), the §274(d) audit trail produced, and whether the data ever leaves the device.

A worked scenario. Robin is a real-estate agent who drives 14 client showings on a Tuesday. With manual logging she would need to open an app 28 times (start + stop). With ADT, the phone records all 14 drives in the background; that evening Robin swipes left for personal, right for business, and the trip log is complete. At the 2026 rate of 72.5¢ per mile, the average showing-day drive of 47 miles becomes a $34.08 deduction logged with zero friction.