Ep 3. Mega City Trains

Mega City Trains is the third episode of the fourth season of Impossible Engineering. The episode dives into the innovative and complex systems behind the world’s largest and most advanced trains, specially designed for mega-cities.

The episode features several remarkable engineering feats, including China’s high-speed urban railway in Shanghai, the impressive MTR transportation system in Hong Kong, and the automated Canadian light rail transit in Edmonton. Through cutting-edge CGI animation and commentary from engineers and experts, the documentary showcases the inner workings of these systems, from the construction to their operations.

The episode takes a closer look at Hong Kong's sensational new cross-boundary railway system, which consists of a 26-kilometer-long tunnel to connect the city's main economic center to the Chinese mainland. The bridge features an undersea tunnel, allowing for uninterrupted speeds of up to 200 kilometers per hour. It required the coming together of different country's engineering and construction expertise, making it one of the most complex mega-projects ever undertaken. The documentary also outlines the innovative solutions used to construct tunnels through mountains and undersea and create a strong foundation for the giant Hong Kong-Zhuhai-Macau Bridge.

Another impressive railway project featured in the episode is the Edmonton's Valley Line LRT. The system was designed to be fully automated, making it the first of its kind in North America. The automated trains are designed to reduce the amount of time commuters spend idling at stops, as well as improve their on-time performance and efficiency. The segment on the Edmonton Valley Line LRT delves into the innovative software and hardware systems needed to run the trains without human conductors, from sensors to communication systems, and power supply.

The documentary concludes with a third mega-project, the Shanghai Donghai Bridge Rail Transit or SDBRT. The rail system is capable of serving over 300,000 passengers per day, making it vital to the region's transportation infrastructure. The episode investigates how the infrastructural design was achieved, the stringent safety guidelines, and the strategies put in place to mitigate the severe climatic conditions. It also examines the suspension bridge's unique design, which had unique challenges such as strong sea winds and high seismic loads.

Overall, Mega City Trains is an eye-opening showcase of the biggest and most technologically advanced railway engineering projects in the world. With extraordinary Behind-The-Scenes footage and expert insights, it's a must-watch for anyone interested in engineering feats and technology.