A rumpus - perhaps even a fracas? - involving multiple carriages.
Assassin's Creed Syndicate Sequence 5 - Friendly Competition
This mission begins after you speak to a woman at the waypoint. Drive carefully to the next waypoint and watch carefully - your target will make for the hills in a carriage while two more attack the second omnibus.
Optional challenge: put down the two enemy carriages and defend the second omnibus before proceeding.
Chase after your target. The easiest way to take them out - and the two other carriages, by the way - is to get close enough and lob a throwing knife. A pistol works too, but you're far less likely to get a one shot kill.
Travel on to the next waypoint. You'll be tasked with destroying the omnibuses. Start by scouting the yard from the eastern railroad tracks just outside the restricted area. Use Eagle Vision to spot a couple of crates of explosives.
Your ultimate goal is to push the cart in the middle, but you'll be spotted instantly if you do that; you need to take out a bunch of baddies first. You can proceed as you like, although take note of the fire if you have a hallucinogenic dart handy. Once the coast is clear, push the cart next to the omnibus.
You'll have ten seconds to leave the area after you interact with the crates to ignite them, so find an exit route first; a quick Rope Launcher is your best bet. If you make it you'll see a cutscene, and the mission ends.