Final answer:
The AVE system uses standard gauge rails to enable direct connections with other railway systems outside of Spain, standardizing operations and safety measures. So, option D is correct.
Step-by-step explanation:
The AVE (Alta Velocidad Española) system utilizes standard gauge rails primarily because standard gauge rails permit connections to railway systems outside of Spain. This decision aligns the AVE system with international rail standards and facilitates interoperability with the wider European rail network. Historically, railroads have impacted national unity and required standardized safety measures. The standard gauge was adopted so that trains could operate across different networks without the need for changing equipment or transferring loads at border crossings.
Another reason is that standard gauge rails make the train safer when traveling at high speeds, as they provide stability and reduce the risk of accidents. Additionally, standard gauge rails make the train easier to stop, which is crucial for maintaining safety and controlling train movements. Standard gauge is the international standard for railway tracks, and using it allows for interoperability with other railway systems worldwide. This facilitates seamless connectivity and operations when trains need to travel across different countries or regions with standard gauge tracks.