Developments in high-speed rail from the 1970s mean that ballast depths have increased, resulting in a present decrease in UK pan-network loading gauge height. This has recently started to be reversed with the introduction of pan-European loading gauge standards on some mainlines, mainly originating from ports. The present result of these civil engineering changes is that an original height King locomotive would not pass through various points of the modern Network Rail system, designed to a loading gauge height of .