Vietnam Railways primarily uses a metre gauge. However, in the North areas of the country, there are also mixed gauge and standard gauge lines. The key route of this line is a 1,072-mile single track (the North-South Railway line). It runs between Ho Chi Minh City and Hanoi.

The Vietnamese railway network is a unique "triple-gauge" system, reflecting its diverse historical and geopolitical influences. The vast majority of the 2,600-kilometer network—approximately 85%—is Metre Gauge (1,000 mm). This includes the iconic North-South "Reunification Express" line connecting Hanoi and Ho Chi Minh City, which was originally established during French colonial rule. In the northern part of the country, particularly on lines connecting to China, you will find Standard Gauge (1,435 mm) tracks to accommodate international trains from the Chinese network. Furthermore, around the Hanoi hub, there are Mixed Gauge (Dual Gauge) lines, which feature three rails to allow both metre-gauge and standard-gauge trains to share the same track bed. This infrastructure allows for seamless freight and passenger transitions from the domestic narrow-gauge lines to the broader standard-gauge international routes. As of 2026, there are long-term plans to build a dedicated high-speed standard-gauge line to modernize the North-South corridor, but for now, the metre-gauge remains the workhorse of the nation's transport, providing a charming, albeit slower, travel experience through the Vietnamese countryside.