Train travellers are poorly served by the UK’s mobile networks, says Ofcom. Tests on railway lines in England, Scotland and Wales revealed disappointing signal across 24 rail segments, with results falling short in 83 percent of cases. 

The communications regulator is now calling for a nationwide effort to raise the standard of mobile coverage passengers can expect.

On-board Wi-Fi was also tested by Ofcom and it performed well just one percent of the time.

This writer can attest that on train journeys to London, the mobile network signal is often too weak to allow doom scrolling on social media - which is perhaps no bad thing.

Ofcom’s report [PDF] found that even the best performing network (EE) met the Good Performance threshold less than half the time, while Three, O2 and Vodafone could only achieve this between 17 and 21 percent of journeys.

For the purpose of the tests, Good Performance was defined as a download speed of at least 5 Mbit/s, an upload speed of at least 1.5 Mbit/s and a response time (latency) of 50 milliseconds or better. This level should allow a passenger to stream video or browse the web without noticeable delays.

Ofcom tested cell performance on main line rail journeys, and most of these were in England, with a few in Scotland and just a solitary line along the south coast in Wales. Northern Ireland was not included in the tests.

According to the results, the best performance was on the London Victoria to East Croydon line, south of the capital, or London to Bristol – but only for EE users.

The problem is down to weak mobile signal strength along rail corridors, which can be further attenuated by certain types of rail carriage, Ofcom says. Rural and intercity passengers unsurprisingly experience a worse service than those in urban areas, where there are more cell base station sites.

However, latency turns out to be the main reason why tests failed to meet the Good Performance threshold. Even when download and upload speeds were adequate, network delays proved to be the bottleneck, Ofcom says.

One aspect of the study relates to the technologies operating across the four networks. EE has a roughly even three-way split between 4G, 5G Standalone (5G SA), and 5G Non-Standalone (NSA), which the report says “represents the most advanced 5G deployment observed in the study.”

Three remains predominantly a 4G network along the rail corridors, accounting for 68 percent of samples, 32 percent as 5G NSA and no 5G SA encountered during testing. Vodafone and O2 sit somewhere between these findings.

Despite Vodafone and Three sharing their networks as part of their ongoing merger, Three users were not able to use Vodafone 5G SA at the time of the survey, Ofcom found.

In the case of Wi-Fi, only South Western Railway, which is testing a trackside millimeter-wave tech, delivered a meaningful service as part of their technology trial, Ofcom says.

Throttling by train operators is too severe, it found, with caps of about 1 Mbit/s on some routes preventing passengers from enjoying Good Performance. The on-board service also used older standards, typically Wi-Fi 4 or 5.

In-train connectivity does not yet consistently meet the expectations of modern passengers, the report concludes, with significant variation by route, operator and time of day.

Improving the experience will require coordination between mobile operators, train operating companies and others, plus supportive policy and regulatory frameworks.

Kester Mann, CCS Insight director for consumer and connectivity, told us: "bringing reliable mobile connectivity to trains is hugely challenging. It requires connecting to multiple masts and other network infrastructure while travelling at speeds of 100 MPH or more. Tunnels and cuttings make the job even more demanding."

He said many tracks pass through rural areas where mobile coverage is weak or absent. "Poor signals on trains is a regular customer frustration that the mobile industry, Government and train operating companies have long struggled to address." 

The regulator wants to hear from interested parties on the issues raised in this report, and welcomes responses between now and July 29.

 “People rightly expect connectivity they can count on - and delivering it will require a joined‑up national effort,” said Ofcom’s Group Director for Infrastructure and Connectivity, Natalie Black. ®