This area is occupied by the Gunners. There’s a terminal in the trailer car in the middle where you can control the spotlights, turrets and lower the crane leading to the broken overpass where more gunners are located.
The garage has a Power armor station and a tripwire fire trap. Inside is a Novice sliding door which will allow you to access a room with a duffel bag with some ammo and explosives.
There’s the weapons workbench in the shed to the south end of the overpass while on the northern side you’ll find Captain Bridget who carries a Fat-Man, three mini-nukes and a heavy Combat armor set. Examining her terminal will allow you to get map markers for locations in The Cannery, Quarry, and Revere.