The Capo Boi - Terra Mala project represents the final segment of the bypass to SS 125 Orientale Sarda (which has origins in Cagliari), concerning the 2nd section of Trunk II, between the Terra Mala junction and the Villasimius/Capo Boi junction. This 6,600-meter section extends from kilometer marker 8+780 of Section 1 to kilometer marker 15+380, where ramps C and D connect the artery to SS 554 at the S. Lianu terminal junction. The project involved various professional profiles, including engineers, surveyors, administrative staff, and workers.

The route starts immediately after the Canaleddus tunnel of Section 1 and includes several significant infrastructures. Among these are the 358-meter Murtaucci Viaduct, the 1290-meter Marapintau tunnel, the 212.50-meter Is Stellas tunnel, and the 2590.50-meter Martineddu tunnel. Additionally, at kilometer marker 15+140, there is the 75.9-meter S. Lianu 2 viaduct.

The road tunnels were excavated using traditional methods with explosives and mechanical means, while the parallel emergency tunnels were constructed with an open TBM. The tunnels are equipped with pedestrian bypasses every 150 meters for a total of 26 connections, allowing for quick evacuation in case of emergency.

An innovation of the project is the installation of an automatic fire extinguishing system using foam in the Martineddu tunnel; this is the first application of such technology in a road tunnel in Italy. The system is controlled by an emergency management system, with strategically positioned nozzles to ensure effective distribution of the extinguishing agent.

The project faced several challenges, including improving the safety of the tunnels and energy efficiency. The construction of emergency tunnels parallel to the Marapintau and Martineddu tunnels allows for rapid evacuation, while the advanced technologies employed aim to reduce electricity consumption and CO2 emissions. The foam fire extinguishing system underwent rigorous testing in collaboration with the Polytechnic University of Turin to verify its efficiency before opening to traffic. Additionally, the construction site was visited by students from the University of Cagliari and the Polytechnic University of Turin, who studied the reuse of granite material as a road sub-base.