Odometer Clocking Detection
Status: planned. Method below; results to follow.
The problem
Clocking means winding back a car's odometer to inflate its resale value. Every MOT test records a mileage reading, so each vehicle's test history forms a time series that should only ever go up.
Approach
Readings are ordered by test date for each vehicle, then checked against rule-based flags, similar to first-line fraud rules in lending.
| Flag | Rule | Likely cause |
|---|---|---|
| Rollback | Reading lower than previous test | Clocking, or keying error |
| Digit error | Reading roughly 10× the previous | Extra digit typed |
| Unit switch | Miles and km mixed across tests | Data entry |
Why it's harder than it looks
- Not every drop is fraud: replaced instrument clusters and tester typos produce genuine-looking rollbacks.
- There are no confirmed fraud labels, so the flags can't be scored the way a PD model is scored.
- Instead, precision will be estimated by manually reviewing a random sample of flagged vehicles.