Left 4 Dead/The Train Station

You're in a safe house above a bridge you've just knocked down, and are heading to a train station en route. Ignore the poster saying to go to the airport, that's quarantined location.

Route

 * Exit the safehouse, and head down the path.
 * You can check the barn for supplies, but may be faster to take a right around it. If you check it out, you can use the roof for cover or defence - the exit is marked by two mutilated cows.
 * When you see Richardson Atlantic, climb down onto the tracks again. Follow them.
 * You'll reach a building - you have to enter it, and climd two flights of stairs. Exit by the side window and return to the train bridge.
 * Cross the bridge to reach a safehouse.