The work and the technique: Direttissima Rome - Florence high-speed railway line. Italy

The Direttissima Rome-Florence is a 3kV direct current electrified railway line; it is a reversible working double track, i.e. a line that allows trains to travel in the same direction on both tracks without changing the requirements for train traffic. 

The Direttissima was created as a technologically advanced quadrupling of the pre-existing line. With the latter, it forms a single four-track system, managed as a unit to allow greater operating potential and flexibility.  There are ten interconnections between the Direttissima and the "Slow" line, whose points of origin and termination are known as crossroads. Each junction on the Direttissima is known as first, while the corresponding one on the "Slow" line is called second: each junction is identified with the name of the interconnection to which it belongs.

In the total absence of level crossings and intersections (except at dedicated service stations), the Direttissima has an almost straight layout, with a 4 m space between tracks to neutralise the dynamic effects of trains crossing the line.  The maximum slope is 8% while the minimum curvature radius is 3,000 metres. 

Double interchanges between the tracks every 16.2 km allow either track to be used in both directions or circulation on a single track if necessary. The railway interconnections between the four tracks of the system use overlaps without interference between the routes of the Direttissima.