This paper aims to demonstrate the advantages of the Alternate Double-Single track (ADST) solution with respect to the traditional double track alternative for railway line design. The paper starts with an introduction and a summary along with a description of the ADST approach and its main advantages. For illustration purposes two real cases, which use this procedure, have been described.

The Santander-Bilbao and the Vitoria-Zaragoza line proposals are analysed in some detail showing the important savings and performances when compared with the double and single track solutions. Finally, some conclusions and recommendations are given.