The European (Berne) loading gauge is usually 3,150 mm (10 ft 4 in) wide by 3,175 mm (10 ft 5.0 in) rising to 4,280 mm (14 ft 1 in) in the centre. This is a clearance envelope (see loading gauge) on a curve of 250 m (820 ft 3 in) radius.
Previously, international through traffic, particularly freight, had been effectively constrained to vehicles and loads consistent with the standard French (with 1,500 V DC) loading gauge, the narrowest and lowest in Mainland Europe. As a result of accepting the convention, the French embarked on a period of progressive upgrade to make their network compliant.
Even after adopting the convention, significant parts of the European network, such as Belgium and most Germanic countries, as well as Scandinavia, operated to larger gauges, thus limiting the passing of traffic out of such areas.
Although the name "PPI" includes the characterisation as "international" it is actually the minimum standard just in Western Europe. The contigious rail network in Northern America has a minimum width of 3250 mm (10 ft 8 in) and a minimum height of von 4620 mm (15 ft 2 in). The standard gauge rail network in Eastern Asia is built to a minimum width of 3400 mm, thus the chinese CHR2 as well as the japanese 0 Series Shinkansen have a width of 3380 mm. Quite similar the tracks in Sweden are built to 3400 mm (clearance SE-A and SE-B) just as the broad-gauge network under russian influence (on tracks with 1520 mm). As such the Russian Velaro Sapsan and the Chinese Velaro CHR3 have width of 3265 mm while the German variant Velaro ICE 3 is built to 2950 mm to fit in the PPI outline. Since Germany knows a number of oversized freight trains from neighbouring countries some parts of its rail network can easily accommodate wider trains. In a reasearch project for ICE 4 a width of 3300 mm had been tested - but it was never pushed into production.
The success of the intermodal shipping containers did lead to some adapations to allow ISO containers with a height of 2600 mm or even more Hi-Cube containers with a height of 2900 mm to be carried by rail in Western Europe. In general the deck height of flatcars was reduced to 940 mm to allow for shipping containers to fit in the "GB" clearance in France. It was further modified so that for the minimum height of the exterior walls (3175 mm) and the minimum height at the center (4320 mm) a third height was added such that at a width of 2720 mm a minimum height of 4180 mm is ensured. This profile was dubbed "GB+" as having a roof that is almost flat. All modern freight tracks in Western Europe are built to this size being the modern replacement for the PPI being a minimum international loading gauge.