In effect, both height and width are a problem: traditional European loading gauges have a more curved roof section than American ones, and the key for any kind of intermodal is corner height. Making rail lines suitable for high-cube containers (height 9'6" instead of 8') resp. 4-metre standard height European trucks is a challenge in continental Europe, too (for example, in long tunnels in Switzerland, the solution was to lower the trackbed and replace the catenary with roof third rail). Check extended UIC profiles on page 22 of this document, which also shows the British profiles on later pages.

_{*Lunatic*, n.
One whose delusions are out of fashion.}