NR/L3/OPS/301: the rail call recording mandate, explained

For decades, the recording of railway voice communications stopped at the edge of the managed network. Signaller calls, control room lines and GSM-R cab radios were recorded as a matter of course; the mobile phone in a contractor’s pocket was not. Since March 2026 that gap is closed on paper: under Network Rail standard NR/L2/OPS/301 and its NR/L3/OPS/301 modules, safety-critical mobile calls made in connection with work on the infrastructure must be recorded and auditable - whoever employs the caller and whoever owns the phone.

I run a mobile network that has recorded calls at network level since long before this standard existed, so I’ll declare that interest now. But most of what follows is simply what the standard says, who it catches, and the practical choices firms in the rail supply chain have for complying.

This is not legal or contractual advice. Your obligations depend on your contracts and the roles your people hold. Confirm the specifics with your Network Rail contact or principal contractor.

Where the requirement came from

The standard did not appear from nowhere. RAIB’s investigations into track worker safety - including its class investigation into the safety of track workers outside possessions - kept returning to the same theme: near misses and fatalities where the safe system of work was set up, varied or abandoned in conversations nobody could later reconstruct. When the only record of a safety-critical decision is two people’s recollection of a phone call, investigation and accountability both suffer, and so does the discipline of the conversation itself. People speak more carefully on a recorded line. That is not a bug; for safety-critical communications it is the mechanism.

The result was a RAIB recommendation to record the calls that set up safe systems of work, and Network Rail’s answer is the 301 series.

What the standard actually requires

The heart of it is narrower and more specific than some of the marketing around it suggests. Network Rail’s change team has clarified the scope: the recording requirement applies to mobile phone calls between the Controller of Site Safety (COSS) and the Person in Charge (PC) - the conversations on which safe systems of work depend. Duplex plant communication systems and machine-to-controller workflows are not in scope.

Alongside the new requirement, NR/L3/OPS/301/02 replaces NR/L2/OPS/033, the older standard covering recorded communications between possession management and engineering train or on-track plant drivers in possessions - so recording in possessions and the new COSS to PC requirement now live in one framework.

Three practical properties matter for whatever solution you choose:

Coverage. The calls in scope are made by whoever holds the COSS or PC role that shift - frequently agency staff and subcontractors, on ordinary mobiles, far outside GSM-R. A solution that only covers company-issued smartphones with a working app misses the exact population the standard was written for.

Completeness. An auditor, or a RAIB inspector after an incident, will not ask whether you record calls. They will ask for the call - a specific conversation, on a specific date, between two named roles. “The app wasn’t installed on that handset” is precisely the answer the standard exists to eliminate.

Auditability. Recordings need to be retrievable, attributable to a number and a time, and reviewable - a system of record, not a folder of files on someone’s laptop.

The three ways firms are complying

Recorded devices issued per shift. Handsets with recording capability handed to whoever holds the COSS or PC role. It works, but it means device pools, charging, handover procedures and the perennial risk that the recorded handset stays in the van while the call gets made on a personal phone.

Recording apps. Cheap to deploy, and the weakest option for exactly the reasons above: they depend on the user and the device. Every OS update is a silent threat, every native-dialler call is a gap, and proving completeness to an auditor is somewhere between hard and impossible.

Network-level recording. The recording happens inside the mobile network, on the number, not on the phone. Nothing to install, nothing to bypass, nothing that breaks with an update - the handset just needs to work on the recording network, and that includes rugged site phones with no app store as well as ordinary smartphones (our supported devices list has the specifics). This is how control rooms have always recorded, applied to mobiles.

We are, unsurprisingly, in the third camp. ONSIM records every call and SMS on the business number at network level. A worker’s existing mobile number can be ported in and recorded - they keep the number their colleagues already have - or a recorded number can be added to their existing phone alongside their personal one with an eSIM. Recordings, and real-time call logs that include attempted calls that rang unanswered, sit in one dashboard with API access so evidence can be pulled into your own safety management systems.

The honest caveats

No phone service makes you compliant by itself. The standard also concerns role assessment, procedures and how recordings are used - recording is necessary, not sufficient. ONSIM is not “Network Rail approved” and we will not pretend a badge exists that does not; what we provide is the recording, retention and audit capability the standard’s communication requirements describe. Scope questions - which of your people, which calls, what retention your contract specifies - belong with your Network Rail contact or principal contractor, and the answer you get from them beats anything you read on a supplier’s website.

If you hold COSS or PC responsibilities in your contracts and your people are making those calls on unrecorded mobiles today, that is the gap to close. Most SMB recording customers pay £20 a user a month all-in - SIM, UK minutes and SMS, recording and archival - or you can get a quote and we’ll talk through your setup - small contractor or principal, one van or a fleet.