Read Prima's free inFAMOUS: Second Son walkthrough.
The objective is located under the bridge. Use your map and head there to chat with Eugene a bit more. In order to stop the convoy, shoot the four support beams shown on your map. It's not the larger beams you need to worry about, but rather the small connectors that bind them with the bottom side of the bridge.
You need to stay on the road for this battle. Move forward and into the collapsed part of the road where you can take cover from the D.U.P. forces. Use your Phosphor Beam to take out the armored vehicle up the road from you. From here on out, use the debris and destroyed vehicles for cover from the D.U.P. agents. When they start throwing up rock shields, be patient and wait for a clear shot. If you do run out of Neon, there should be plenty of Smoke nearby to keep you in the fight.
When you've cleared everyone off the bridge and checked the bus, talk to Eugene before getting to high ground. Press Up on your directional pad to use the signal tracker. Adjust the direction you're facing until the bar is full and then head that way. Keep checking every time you get to a new building to make sure you're still headed in the correct direction; it seems some objectives move.
When you reach your destination, there’s quite a lot of D.U.P. in the area. If you managed to string a Good Karma streak together, consider dropping into the middle of them and using the Radiant Sweep by pressing Down on your directional pad. Otherwise, stick to the high ground and start picking off agents one-by-one.
Tip: If you have any Blast Shards, think about upgrading your Neon and getting Laser Focus, allowing you to slow down time and improve your accuracy. Combining your Phosphor Beam and Laser Focus is a devastating combination that can quickly put these guys to rest.
After searching the second bus, you'll be ambushed by three very large D.U.P. agents. These guys mean business. Use your Light Speed to get to high ground, just be aware that they will follow you no matter where you go.
The best way to take these guys out is to quickly move from one building to another. When they jump to the roof you've recently moved to, utilize your Laser Focus to get some good shots in before using your Light Speed to get away. The strategy remains the same if you don't have Laser Focus (or happen to be using Smoke). Just be sure to make good shots and utilize your melee attack when they get close.
When the battle is over, use your cell phone to track the next bus and search it. This one's empty, so get back to the high ground and find the signal for the final objective.
When you arrive at the final location, there will be D.U.P. agents scrapping it out with angels. Focus on the D.U.P. agents, they are the real threat. The angels will leave you alone. Use the same formula here as you have in the past, stick to the high ground and keep moving. When the final D.U.P. is down, head to ground level to check the final bus and complete the mission.