The fact that cell phone coverage in trains is weaker than outside has to do with the concept of the 'Faraday cage' from physics: a metal casing - like a train car is one - is harder to penetrate by electromagnetic radiation, which results in a fierce reduction of the electromagnetic signal. So achieving 100% mobile coverage in trains is very difficult. Coverage can be improved by building new antennas along the railroad lines. Proximus has made significant efforts here in recent years, focusing on the main train lines. Whenever a new antenna site is built by an operator - whether along railroad lines or not - there is a legal procedure that allows the other operators to place an antenna on the same site / mast. In such a case, the site (not necessarily the antenna) is thus indeed shared. Each operator makes its own choice in this respect, depending on the needs of its mobile network in terms of reception and capacity. Technological developments are also leading to improvements. Today, many mobile devices are already equipped with VoLTE technology: using the 4G network to handle a phone call. Proximus has measured in its train tests that this newer technology also provides a better experience on the train, largely explained by the fact that 4G technology uses a slightly lower frequency (800Mhz): a lower frequency goes a little easier inside a 'Faraday cage'. Slowly but surely, there is an evolution away from the 'classic' GSM handsets, towards this newer technology. The same goes for the use of mobile data: the newer devices can handle 4G, which works much faster than the older 3G or 2G devices. The technological update to 4G is 99% complete on the Proximus network. And 5G also promises an improvement in data speed and reception, especially when the 700 MHz frequencies become available after the government auction.