Research from US firm Global Wireless Solutions (GWS) has found that UK mobile operators struggle to provide a decent service on commuter lines in and out of London.
A GWS Commuter Connectivity Map of London trains shows clearly that commuters often have difficulty retaining mobile connections for data and voice calls when travelling to and from the capital.
GWS engineers studied the main commuter lines around and in London and found that one in three internet tasks, and one in seven phone calls, failed during the journeys.
GWS also carried out a series of upload and download tests, and O2 and Three both performed worst on these tests, with the slowest speeds over 3G and 4G. Both operators also fared worst for the reliability of 4G data packets, although EE came last for the same tests over 3G.
The best performing provider for calls on trains was Three, while Vodafone was credited for its 3G services, and EE topped out the 4G table.
However, GWS found that in most instances the mobile providers rely on 2G networks for commuter services. O2 was deemed the worst of the providers, putting callers on 2G about 60 percent of the time.
In its defence, O2 said, "We continue to invest £1.5m every day in our network, growing our 4G network and completely modernising our 2G and 3G networks. This work is delivering faster speeds and greater coverage across the UK, ensuring our customers have a great network experience."
The worst performing station was St Pancras, and GWS expressed its surprise that such an important hub should be so poorly served.
"Commuters have enough to contend with without the kind of mobile connectivity problems we're revealing today," said Paul Carter, chief executive of GWS.
"It's hard to believe we're in 2014 and in a situation whereby a trained wizard would have a tough time getting a signal on the Hogwart's Express while it's sitting in St Pancras. Pressure from commuters makes it inevitable that trains won't keep their status as mobile dead zones for much longer.
"It'd be great to see networks, rail operators and station-masters taking the lead on improving connectivity for commuters."
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