Left 4 Dead/The Subway

From the safehouse, you need to travel in the subway tunnels to cross a portion of the city. The next safe house between you and mercy hospital is a pawn shop.

Walkthrough
Most of the travel on this map before the generator room - aside from the initial subway platform, there is only one route available, and the minor branch only determines which side you use to enter the railway.

Upon leaving the safehouse, you will immediately drop down one floor; there may be zombies that are hidden under the dark area behind you. From this location, you can take the stairs directly down, or take the passage through the right (and ventilation shafts) to the lower station.

Collect items in this region (there is usually pain pills or a grenade) and pass through the turnstiles. Climb the stairs either to the left or right, and walk along the rail line; you should come to an ammo pile after the second room.

From this ammo pile, follow the tracks to the right, and walk through the carts. Climb up the stairs to reach the basement, and refill from the second ammo pile. Head up the stairs to the generator room.

The generator room will attract the horse as soon as you flip the switch. To defend, take any gas cans, and place them at common access points (e.g. behind the minigun, or at other positions.) There is also likely to be molotovs near the door to the basement. Once the generators start, the door will open within 30 seconds, and you will be able to head into the stairs to the upper floor. If you are playing the demo, the game ends here; otherwise, you will need to continue through the building to the street, before you can reach the safehouse.

Respawn points

 * Between the generator room's basement and the set of trains is a respawn point.

Survival
The survival mode for this map covers three regions; the initial basement below the generator room, the main generator, and the upper floor once the generator door opens after 35 seconds. The exit of the upper floor is barricaded, as is the back room of the upper floor.

Enemies enter through ceiling holes within the basement, or from the upper floor in the generator room. Since the basement is dark, you may find it difficult to detect incoming enemies, as well as falling back to a different location in tactical retreats. The mounted gun, while powerful, is impractical for holding out, since it requires a person watching the floor from behind the gunner. In addition, the nest will have to be evacuated if a tank approaches from behind.