That's a lot of people to move, so the city has long relied on rail transit lines to help it meet both its logistic and sustainability goals.

Now, the Malaysian capital is investing another USD$388 million in its rail network, and adding another 27 of manufacturer Bombardier Transportation's all-aluminium Innovia Metro 300 rail cars to its fleet.

The flexibility allows them to run with just one passenger car or up to six of them; the trains can move 30,000 people per hour in the same direction of travel in the four-car model Malaysia plans to use, and they operate at speeds up to 100 km/h.

Those new vehicles will bring to nearly 400 the number of vehicles that Malaysian officials have put in service through Bombardier and local partner Hartasuma, which finishes and services them locally.

The Metro 300 is a lightweight aluminium component of rail systems designed for a mid-range market and ridership. The driverless, fully automated trains work harder than light-rail trams designed for lower capacity, while proving to be more cost-efficient than high-capacity metro lines that don't quite fit.

The increased rail capacity is part of Malaysia's overall economic development plans, and this latest upgrade introduces new-generation trains to a system originally built in 1998. That system was built ahead of the Commonwealth Games, and was designed to connect both the eastern and western suburbs through downtown on the Kelana Jaya Line. It connects 24 stations along a 29-kilometer route, and currently carries 220,000 passengers per day, which is expected to rise with the four-car capacity.

In addition to using lightweight aluminium and other highly recyclable, no-waste materials, the Metro 300 features regenerative braking systems that allow for up to 95 percent energy recycling.

They also boost added security features including CCTV and two-way radio contact, modular seating arrangements to accommodate passenger volume, and lower floors for easier passenger accessibility.

The project is another example of how rail systems have followed the aviation and auto industries in seeking the greater fuel efficiencies associated with lightweight aluminium – and reduced the impact on emissions and the environment.

Bombardier is joined by Constellium, a European aluminium producer, and other industry leaders who are advancing the role of aluminium in rail and transport systems. The TGV Duplex in France, Canada's LRC, Japan's Hikari Rail Star, and London's new Crossrail system are all examples of railway cars and systems that rely on aluminium – the material chosen for more than 80 percent of Western Europe's railway carriages.

The first trains in the Crossrail system are now set to run through London in December 2018, which will reflect the culmination of a transport infrastructure project that first began in 2009. According to the January 2017 update, in addition to train station and track work completions, the first of the new trains are being tested at the Ilford depot – and even Prince William has had the chance to give one a spin.

That train will go into service next month between Liverpool Street and Shenfield on a London commuter line. As with Kuala Lumpur, the London trains are manufactured by Bombardier and share both their aluminium construction and many of the same energy-saving technologies and features.