What I learned from WTN App

WTN App was my own product: digital waste transfer notes for UK producers, carriers and consignees. Building it worked, and a lot of what I know about sync and about software for the field comes from it. Selling it did not work. Sync, short for synchronising, means that different devices and the server end up with the same data, even when they are not online at the same time.

Who it was for

Every load of skip-hire, scrap and construction waste in the UK travels with a waste transfer note. For decades that has been a paper form, and the UK is moving it to digital tracking. A lot of the operators affected are small: single-truck owner-operators, family-run skip-hire companies, regional fleets of two to twenty vehicles.

The idea was an app that worked the way the job works: outside, in the rain, in basements with no signal, with gloves on.

What I built

A four-step signature chain that followed a load from producer (the building site, the office, the factory) to carrier (the driver) to receiver (the transfer station), and then into a searchable archive. The app could search the European Waste Catalogue, with sensible defaults for the most common loads. If a load contained hazardous material, it generated the extra consignment note. Every party could get a PDF, and carriers got the quarterly returns they used to assemble by hand.

I owned the whole thing: the mobile app, the web dashboard for fleet managers, the data model, the back-end and the support inbox. So whatever came into that inbox reached the same person who wrote the code. I also sat on calls with drivers, and I changed things when they told me something did not work in the cab.

How it worked with no signal

A driver could take a load, sign it and hand off to the next party with no signal at all. The chain reconciled when any party came back online.

The handoff used a QR code that was only valid for a short time. It held the number of the chain and a check value, calculated from the producer’s data at that moment. The carrier scanned that code with no network. A check value like that lets you verify later whether the data is still the same.

Every chain had a log that only ever gained new lines. Existing lines were not overwritten. The server worked out the current state of the chain from that log, and the phone had a small database on it, so the app kept working with no connection.

Each role had fixed fields it could change. Producers edited producer fields and carriers edited carrier fields, and nobody could re-sign for someone else. That way, two parties working offline cannot end up in the same field.

Every screen had a badge with three states: saved locally, sent to server and confirmed by all parties. That showed you how far your change had got.

For owners, this is explained in An app that works with no signal, and for developers in Offline-first mobile sync.

How it ended

People started signing up, but they did not go through the whole platform. I never found out why. There was some traction, but never what I had expected. Sales did not follow, I did not want to pick up the phone and start dialling, and after a while I lost interest. I no longer work on it and the app is no longer maintained.

What I would do differently

I would first look for a sales partner in the UK: someone who takes on the language and the communication, knows the waste industry and does the outbound work, because I think more of that was needed. I still don’t know why people dropped off, so I can’t say whether that would have been enough.