# Inside a High\-Speed Train Station

How a high\-speed station hides its power, air, signal and drainage systems beneath a plaza, shown track by track from the concourse down to the sump\.

By sunny\-moon\-1ce2a64b

Topic: Engineering

[Open the interactive Jig](https://ask.jig.com/j/EI1N5LbawoYA)

## Transcript

### 1. Inside a High\-Speed Train Station

Most people only ever see a station's bright halls\. This one is laid out like Shanghai Hongqiao, with many tracks side by side and lines arriving from several tunnels\. Beneath the plaza hides a whole machine of power, air, signals and water\. Let's slice it open\.

Drag anywhere to turn the station\.

### 2. The tip of the iceberg

From the street you see a plaza, a glass entrance and a drop\-off road\. Taxis stop in the lane beside the kerb and private cars in the outer lane, so neither blocks the other\. Travellers step out and follow the green arrows inside\. At Futian station in Shenzhen, the platforms lie about 32 metres underground\.

The station is shown shortened\. Real high\-speed platforms can be 400 metres long\.

### 3. The concourse

Stairs lead down to the concourse, the big hall where people buy tickets and wait\. Following the green arrows, travellers pass a ticket gate, which opens only for a valid ticket, then ride the escalator, a moving staircase, down to the trains\. Arriving travellers follow the blue arrows up the stairs and back out through the gates\.

### 4. Island platforms and tracks

Six tracks and three island platforms stand in for Shanghai Hongqiao's 30 tracks\. Eleven trains take turns: each comes out of a tunnel through the throat, a fan of switches \(movable rails that steer a train onto another track\), stops at a platform, then leaves\. Some run straight on, others turn back the way they came\. Bring in a train to follow one through the switches to its doors\.

From Hongqiao, the next stop towards Beijing is Kunshan South, and towards Hangzhou it is Songjiang South\.

### 5. Power from above

A wire hangs 5\.3 metres above the rails, carrying 25,000 volts\. On the train's roof, a folding arm called a pantograph presses a carbon strip up against it\. The electricity drives the motors and flows back through the rails\.

That is more than a hundred times the voltage of a home socket\.

### 6. The substation

In a hidden plant room, transformers change high\-voltage power from the city grid into the gentler kinds the station needs\. Switchgear, cabinets of giant switches, sends it along cable trays to lights, escalators, fans and signals\.

### 7. The station breathes

A fast train in a tunnel pushes air ahead of it, like a piston in a pump\. Huge fans and tall shafts let that air out and draw fresh air in\. If there is ever smoke, the same fans pull it away from the platforms\.

### 8. The signal room

Trains this fast cannot stop just by sight, so computers keep them safely apart\. Small beacons between the rails, called balises, tell each passing train exactly where it is\. In the control room, staff watch every train on a live track map and set its route\. Point machines, motors beside each switch, then move the rails into place\.

From 300 km/h, a train needs several kilometres to stop\.

### 9. Down in the deepest pit

Rain and groundwater seep into tunnels, so channels guide every drop to a sump, a collecting pit at the lowest point\. Pumps switch on by themselves and lift the water up to the city drains\. Next time you wait on a platform, picture the hidden machine around you\.