After exiting the hospital and trapping zombies inside, Newbie sees a helicopter and tries to get its attention. He follows the helicopter, ending up at a broken bridge
It can be found on top of the first bus. You can either parkour to the top or use either your Signal Pistol or a grenade.
It's in the green dump truck hanging on the edge of the bridge. Make sure to not accidentally walk off.
This is a bridge that has collapsed, with a medical tent and a giant mechanical gate in the back, behind where the player spawns. The rest is an assortment of crashed buses, cars, and police cars. Some cars have their headlights on. There is a room with bloody bags in the tent, presumably containing bodies.
Do not get too close, as the monsters will hit you.
Kill the monsters as quickly as possible, since you can earn a star by killing monsters quickly. Do not rush it, though.
Use pets, as a minor/major backup for killing.
Follow the green arrow that appears once there are 5 enemies left, in order to kill the enemies as fast as possible.
Restore your ammunition by quitting the level and coming back. However, try not to do this when you are about to complete the level, as the number of killed monsters will be wasted.
Use Armor. If you have a decent amount of armor, you will not have to worry about getting damaged, because you can get 3 stars even if you have damaged armor. This doesn't apply to Health.
The enemies aren't extremely tough at this level, so you can equip the weapons with a decent amount of damage.
However, almost all of the enemies appear at the end of the big part of the broken bridge, so it is best to pick them off from a decently long range.
Dodge the explosive wheels of the Infected Truck Driver.
Try to climb the bridge, and attack the boss with a high DPH sniper rilfe
This seems to be based on the Golden Gate Bridge in the San Francisco Peninsula, in the USA.
At the last pick-up truck that is starting to fall off of the bridge, if you use a weapon that can do Rocket Jump, you can launch yourself over the gap and onto the other side of the bridge.
From the aerial view of the map, you could see "2525" on top of the first bus where the hidden coin is.
This bus also appeared in City.
The code 2525 is a reference to the Disney movie, Bolt.