The investment will be distributed with 84.7 million euros allocated for tunnel works and 70.2 million for the renewal of signaling equipment on the section between Atocha and Humanes.

The tunnel works contract includes two main projects: civil engineering for tunnel adaptation and civil protection and safety installations. Both plans have been jointly designed to optimize execution times and prevent interference.

In the Atocha-Las Águilas tunnel (9.8 km), 12 new emergency exits and 13 safe zones will be built. The Méndez Álvaro tunnel (1.8 km) will receive one emergency exit and three safe zones. The Doce de Octubre tunnel (1.6 km) will feature two safe zones, and the Puente Alcocer tunnel (2.1 km) will add four emergency exits and six safe zones.

These improvements will include integrated LED lighting, emergency signage, reinforced electrical supply, communication networks, evacuation corridors, and anti-intrusion systems. Hydrants will also be installed, and ventilation and fire detection will be enhanced.

The signaling upgrade on the Atocha–Humanes section (25.2 km) involves installing state-of-the-art equipment, including new electronic interlockings, LED signals, a new block system for bidirectional circulation, track circuits, and the Asfa Digital traffic management system. The line will be prepared for the future implementation of ERTMS level 2.

These works are part of the comprehensive renewal plan for the C-5 line, which foresees a total investment of 1.35 billion euros, of which 650 million are for Adif's actions aimed at increasing the infrastructure's capacity and reliability.