Roads are paid for by the repair, but proof of the repair is a photograph and a form. A few sealed pellets and a phone could make it physical.
Road maintenance is paid by the patch, but the proof that a patch was made, to what depth and with what material, is usually a photograph, a form and trust. City audits of pothole programmes (one example) review how repairs are tracked and signed off. Computer vision can now spot potholes from vehicle video, but a camera cannot see what is under the surface: a thin skim of cold mix over a loose hole looks the same, on day one, as a proper repair.
Where roads are repaired by contractors, and where citizens complain of potholes returning within weeks, the gap is not detection. The gap is proof that a repair was actually made.
“Every patch should carry its own receipt, buried in the patch.”
Each bag or tub of repair material ships with a small set of sealed ferrite or magnet pellets. The crew places them at set depths as the hole is filled and compacted. The arrangement is the code: how many, and at what spacing, identifies the job and the layer. An inspector, or any resident, holds a smartphone over the patch. The phone’s built-in magnetometer reads the pattern, and a simple app reports “Pattern found. Job 4821. Two layers.” or “No pattern.”
No new hardware is needed on the inspection side. The phone in the inspector’s pocket is the reader.
The crew fills the hole in layers. At the bottom layer and at the top layer they press in a pellet set from the bag, using a printed template for spacing.
Pellets are sealed in a binder and sized to be compacted with the mix. They do not change the repair method.
The inspector holds the phone flat over the patch for a few seconds. The app reads the magnetic pattern and the depth class.
The code matches the job in the maintenance log. Payment, defect liability and complaints can all point to the same record.
| Component | Possible material | Purpose |
|---|---|---|
| Tag | Sealed ferrite pellet or coated magnet disc | A magnetic signature that survives compaction and weather. |
| Code | Count and spacing of pellets, set by a template | Identifies job and layer without electronics. |
| Reader | Any smartphone magnetometer plus a small app | No special inspection equipment. |
| Record | Job ID, location, time, layer, crew | Ties payment and warranty to proof of work. |
The same receipt works for utility trench reinstatement, which cities also have to inspect, and for drain covers and kerb repairs. A city that can say “this patch carries a receipt” can pay for results, enforce warranty, and answer a citizen’s complaint with evidence. A contractor who does the work properly gains a way to prove it.
Each element below exists. The combination — a buried, phone-readable magnetic receipt for each repair — was not found in the search described in the note at the end of this page. That is “no exact match found”, not a guarantee.
| Area | What already exists | What it does not do |
|---|---|---|
| Pothole detection | Computer-vision systems map potholes from vehicle video, e.g. iWatchRoad. | Sees the surface only; cannot confirm what is under it. |
| Repair audits | City audits and accountability pages track work orders and photos. | Rely on records and photographs, not on a physical mark inside the repair. |
| Tags in pavement | RFID and similar tags are used in some asphalt batch-tracking and pavement-maintenance research. | Not found as a magnetic, phone-readable repair receipt for individual patches (no exact match in search). |
Signal strength. A phone magnetometer reads small fields. Whether a small ferrite pellet is readable through the depth of a patch, and how strong the pellet must be, is a measurement question to settle first.
Magnetic noise. Reinforcing steel, utility covers, buried pipes and vehicles all disturb magnetic readings. The pattern design must tell tags apart from clutter.
Debris. If a patch fails, loose pellets must not become hazards or contaminate the surface. Binder and size choices matter.
Cheating. A dishonest crew could scatter pellets on a thin patch. Layer depth classes and a second scan after compaction help but need testing.
A municipal public-works team or state road agency willing to run a pilot on one ward or one corridor, paired with a materials engineer and a mobile developer. A civil-engineering department with a pavement lab can test whether tags survive compaction, heat and traffic. A first trial is simple: tag a hundred patches, scan them monthly, and compare with ordinary visual inspection.
The value is not the magnet. It is a repair record that cannot be written without doing the repair.
Developed by NextGen Economics and checked against public prior art in October 2026. No exact match was found in that search, which is not proof that none exists — if you know of one, please write to us and this page will be corrected. Released freely: no patent, no equity, no permission needed.