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  "description": "When Les Echos and BFM reported that SNCF's TGV-M trains (branded Avelia Horizon by their manufacturer Alstom) were too tall for Italian tunnels I could scarcely believe it. This news came in the same week as SNCF received some good news that they can get a package of guaranteed high speed paths to operate in Italy from next year.\n\nSo I set about trying to work out whether the media reports are true.\n\nFirst some background.\n\nThe issue relates to the loading gauge of the TGV-M trains - the width,",
  "path": "/confirmed-sncfs-alstom-built-tgv-m-avelia-horizon-trains-are-too-large-for-some-italian-rail-lines/",
  "publishedAt": "2026-03-14T17:10:08.000Z",
  "site": "https://jonworth.eu",
  "tags": [
    "Les Echos",
    "BFM",
    "operate in Italy from next year",
    "loading gauge",
    "_direttissima_",
    "between Roma and Orte on OpenRailwayMap here",
    "mapped here",
    "This is the data for the section through Monterotondo-Mentana",
    "Avelia Horizon is 4320mm",
    "see this diagram to explain that one",
    "from this",
    "RFI",
    "more on Flickr here",
    "Loading gauges for railway clearance G1 (International) and G2 (Germany)",
    "Christian Lindecke",
    "CC BY-SA 3.0",
    "Oliver Blanthorn on Mastodon",
    "Joel Haasnoot",
    "PGLux",
    "finding a picture of the GB loading gauge label on a TGV-M"
  ],
  "textContent": "When Les Echos and BFM reported that SNCF's TGV-M trains (branded Avelia Horizon by their manufacturer Alstom) were too tall for Italian tunnels I could scarcely believe it. This news came in the same week as SNCF received some good news that they can get a package of guaranteed high speed paths to operate in Italy from next year.\n\nSo I set about trying to work out whether the media reports are true.\n\nFirst some background.\n\nThe issue relates to the loading gauge of the TGV-M trains - the width, height and curvature of the roof of the trains.\n\nNo one is disputing that the TGV-M trains can operate on modern high speed lines in Italy, and that is where they will run every day. The issue relates to diversionary routes in the case that the high speed line is inaccessible for some reason (a broken down train, landslide, power failure etc.)\n\nThis is especially pertinent between Roma and Firenze - the oldest section of the high speed corridor, generally known as the _direttissima_. This line intersects with a parallel older and slower line in multiple places, and the operational concept for the line is that trains can enter and exit the _direttissima_ as required. You can see this between Roma and Orte on OpenRailwayMap here - red is the _diretissima_ , orange is the older main line:\n\nScreenshot of OpenRailwayMap showing lines due north of Roma, with line through Monterotondo-Mentana highlighted\n\nSo how do you work out the loading gauge of each section?\n\nHere you need to use the EU Agency for Railways data - mapped here. You need to click on a section of line on their map, then click on Track in the pop-up. This is the data for the section through Monterotondo-Mentana highlighted on the map above, and then scroll down to Gauging - G1. The _direttissima_ is G2.\n\nPlease note here there might well be other sections of line with the same problem - this was simply the first one I found to illustrate the issue.\n\nBut what do G1 and G2 that mean? This helps:\n\nDiagram showing G1 and G2 loading gauges\n\nThe important issue: G1 maximum height is 4280mm, and a Avelia Horizon is 4320mm. 40mm, or 4cm, but still too tall. That is the difference between hitting a tunnel or not. All TGV double deck designs have been _at least_ GB loading gauge (see this diagram to explain that one - but simply put it is bigger than G1). I was first told TGV-M is GB gauge from this and I can confirm it with my own slightly blurry picture:\n\nTGV-M in Tournai - note the GB label\n\nSo - simply put - if and when there is a problem on the high speed line, a TGV-M cannot simply be switched to the older main line instead. A Trenitalia Frecciarossa or Italo high speed train - all single deck designs - can.\n\nIs that really a problem?\n\nIt's hard to say.\n\nThe Italian network operator RFI thinks it is a problem, as it would require an alteration to the operational concept of its infrastructure. The procedure for what to do with a TGV-M when a line is closed would be different to the procedure for other trains, and could mean that services operated with a TGV-M would simply be terminated early in the case of a disruption, rather than being re-routed.\n\nRe-engineering either the TGV-M to lower the roof of the carriages, or making loading gauge adjustments to the older routes, would both be theoretically possible, but would be very costly - and hence I cannot imagine either being pursued as solutions here.\n\nOverall I do not think this is going to be a show stopper for SNCF's efforts to enter the Italian market. In the end RFI will probably relent.\n\nBut - strictly speaking - yes, it is true. SNCF's Alstom built TGV-M Avelia Horizon is too large for some Italian railway lines.\n\n* * *\n\n### Image Licensing\n\nTGV-M picture by Jon Worth - more on Flickr here. Map from OpenRailwayMap, adjustments by Jon Worth. Loading gauge diagram: Loading gauges for railway clearance G1 (International) and G2 (Germany) by Christian Lindecke, 21 May 2009, CC BY-SA 3.0.\n\n### Credits\n\nOliver Blanthorn on Mastodon, and Joel Haasnoot and PGLux on Bluesky for helping me get to the bottom of all of this. Thanks Martin Hoffmann for finding a picture of the GB loading gauge label on a TGV-M.",
  "title": "Confirmed: SNCF's Alstom built TGV-M Avelia Horizon trains are too large for some Italian rail lines",
  "updatedAt": "2026-03-14T17:50:15.932Z"
}