Before You Board: The Comfort Rule
Unlike the High Speed Rail, TRA trains vary hugely in age and rules. Most travelers simply swipe their EasyCard to enter the gate, check if the train is going North or South, and then look at the platform screens. However, to ensure a comfortable trip (and avoid fines), you must recognize the train types.
1. Always OK: Local Trains
These correspond to the "Commuter" trains. You can always use your EasyCard/iPASS. There are no reserved seats; you just hop on and find a spot.
Local Train (區間車)
Stops at every station. Cheap and slow.
Photo by: Chi-Hung Lin | License: CC BY-SA 3.0
Photo by: Lokseng01 | License: CC BY-SA 4.0Fast Local Train (區間快)
Skips smaller stations but costs the same as a local train. A hidden gem for budget travelers!
Source: 交通部鐵路局
2. Standing OK: Old Express Trains
These are the older generation of express trains. You have two choices: Buy a reserved seat ticket, OR swipe your EasyCard and stand.
Old Tze-Chiang (舊自強號)
Recognizable by its older, often push-pull style engine.
Source: 交通部鐵路局Chu-Kuang (莒光號)
The orange train. Slower than Tze-Chiang but stops at fewer stations than Local trains.

Where to Stand? (The Deck)
If you use an EasyCard, you generally cannot sit down. You should stand in the area between carriages (the deck/vestibule area) so you don't block the aisle.
3. ⚠️ RESERVED ONLY: The 'Forbidden' Trains
Warning: You CANNOT use an EasyCard/iPASS for these trains. You MUST buy a specific ticket (via App, Kiosk, or Counter). If you swipe in and board these, you will be fined and asked to leave. Conductors check tickets very frequently here.
New Tze-Chiang 3000 (新自強3000)
The newest white and black minimalist train. Very comfortable, but strict rules.
Source: 交通部鐵路局Puyuma (普悠瑪)
The red-nosed train, famous for speed on the East Coast.
Source: 交通部鐵路局Taroko (太魯閣)
The rounded white train, also built for East Coast speed.
Source: 交通部鐵路局
Summary: How Locals Do It
Most people just tap their card to enter the station first. Then they stand on the platform and observe. If an older train comes, they hop on (standing). If a shiny new EMU3000 comes, they wait for the next one. Of course, for long trips (like Taipei to Hualien), we strongly recommend booking a ticket in advance via the 'TRA e-booking' App to ensure you have a seat.