EN 45545-1: Vehicle Classification & Operation Categories (HL1, HL2, HL3)

EN 45545-1 is the foundational document of the European railway fire safety series. Before selecting a single screw or fabric, engineers must use Part 1 to determine the vehicle’s “Risk Profile.”

This standard classifies railway vehicles based on their operational environment (e.g., how many tunnels they pass through) and their design architecture (e.g., double-decker vs. sleeper). The intersection of these two factors yields the mandatory Hazard Level (HL), which dictates the strictness of material testing in Part 2.

1. Operation Categories (OC): The Tunnel Factor

The primary risk factor in railway fire safety is evacuation capability. If a train is in a long tunnel, passengers cannot easily escape. EN 45545-1 defines four Operation Categories based on tunnel length and evacuation infrastructure:

• OC 1: Vehicles operating on infrastructure where evacuation is possible at any point with minimal delay (e.g., Trams, City Metros with side walkways).
• OC 2: Vehicles operating in tunnels or elevated sections up to 5 km in length. Side evacuation is possible.
• OC 3: Vehicles operating in tunnels longer than 5 km where evacuation is restricted.
• OC 4: Vehicles operating in tunnels longer than 5 km where evacuation is impossible (rare category).

2. Design Categories: Vehicle Architecture

Not all trains are built the same. A fire spreads differently in a double-decker coach than in a standard saloon. The standard defines:

• N (Standard): Standard single-deck vehicles.
• A (Automatic): Automated vehicles with no staff on board (e.g., Driverless Metro).
• D (Double Deck): Vehicles with two passenger levels (Vertical fire spread risk).
• S (Sleeping): Couchette or Sleeping cars (High risk due to sleeping passengers).

3. Determining the Hazard Level (HL)

The Hazard Level (HL1 to HL3) is calculated by crossing the Operation Category with the Design Category. HL3 represents the highest danger level, requiring the most flame-retardant materials.

4. Primary Safety Objectives

EN 45545-1 also sets the philosophical goal of the entire standard. The vehicle layout and materials must ensure that:

1. Passengers and staff can survive a fire without permanent injury (e.g., smoke poisoning).
2. Evacuation can be completed unaided (Self-Rescue) within the calculated available safe egress time.
3. The fire’s heat release is limited to prevent flashover before evacuation is complete.