Hanoi has been threading its biggest junctions under the city since 2009, and the resulting underpasses — tunnels built primarily for two-wheelers and light vehicles — are some of the most useful pieces of riding infrastructure in the capital. If your route crosses the centre-south or the southwest, you will use them, and they reward being ridden correctly.
The inventory
The named set so far: Kim Lien, on the central Ring Road 1 at the Giai Phong intersection; Trung Hoa, Thanh Xuan and Le Van Luong across the southwest quadrant’s big junctions; and the newest, the Kim Dong–Giai Phong underpass on Ring Road 2.5, the fifth Hanoi underpass since 2009, opened in the current building wave. More are planned — Hanoi has announced further tunnels for its worst junctions. Each follows the same idea: through-traffic drops under the junction while surface traffic turns above.
Why riders like them
An underpass deletes the most dangerous thing in Hanoi riding — the multi-phase mega-junction — and replaces it with a straight, one-way, lit tube. At rush hour the difference between the surface chaos and the tunnel flow is the difference between two red lights and twenty.
How to ride them
Lights on, every time. Tunnels compress traffic into a tube where a dark bike is invisible; this is the single most important habit.
Hold your line and match the flow. Tunnel traffic runs faster than surface traffic; wobbling or slowing mid-tube creates the danger. Merge in at the entry ramp, pick a lane position, and stay predictable.
Never stop inside. A stopped bike in a tunnel is a collision magnet — the walls hide it until it is very late. If anything goes wrong, coast through or get to the walkway, and deal with it outside.
Mind the merge at both ends. The exit is where the fast and the slow argue: watch for riders accelerating out alongside you, and for the surface traffic you rejoin at the mouth.
One-way discipline. Keep right, dip your speed further than feels necessary, and assume oncoming riders will use more than their half of any shared space.
What not to do
No overtaking in the tunnel’s last stretch, no squeezing between trucks and the wall, no stopping for a phone call. The underpasses are the safest kilometres in the city precisely because everyone treats them simply. Ride them the plain way and they quietly save you five minutes and one junction fight on every crossing.