[SOLUTION CONFIRMED BY PlayazAdvocate IN COMMENTS - Thanks!]
Achievement description MIGHT BE INCORRECT based on the in-game awards announced by the deep-voiced voiceover guy. Maka91's solution is essentially correct, but I was confused at first about "Roadkill" once I started playing. This solution attempts to clear that potential confusion for others with a lot of detail.
For setting up the match properly, keep reading. IF YOU KNOW HOW TO DO THIS, skip the paragraph below and go to the next:
Using 2 controllers, select Multiplayer, Host Match (sign-in a guest controller with "X" at this point), and setup a Vehicle CTF game on Suspense. Game settings under "Server" should be Player Match, Server Type = Listen, Max Players = 2, Min Players = 1, Private Slots = 2. Use RB to get to the "Settings" screen and select Splitscreen = Yes, Bot Combatants = Disabled, Goal Score = 1, Time Limit = 60. [Opposing Bot Faction does not matter & the fact that we chose Max Players = 2 may automatically disable Bot Combatants, but I chose this option anyway to make sure.]
Once the match starts, grab the Scorpion buggy with the controller that has the profile you want the achievement on - Red Team. (You'll know which one is the Scorpion because it's the fastest vehicle on wheels). Drive the Scorpion across the map to very near the opposing flag - Blue Team. Then use the second controller to hoverboard your Blue Team guest player to the front of the Scorpion (most of the time the spawn point for the guest is very near the blue flag)...here's where it gets confusing...
Run over your Blue guest with the Scorpion and the announcer will say "Hit and Run" (in addition to "First Blood"). Huh?? I ran him over once as described in Maka91's solution, but no "Road Kill" award?!?! OK then, let's repeat the process by moving the guest to the Scorpion and run him over again. This time you will get the "Road Rage" award, do it a 3rd time to get "Vehicular Manslaughter", and finally a 4th time and you will finally get "Road Kill". There's that "Road Kill" award! Jump out of the Scorpion, cap the blue flag and hoverboard it all the way back to your base to end the match and get ready for the next. So I just run over my guest player 4 times in the next match, right? WRONG!!!
BEFORE YOU GO ON, NOTE THAT I DON'T BELIEVE THAT YOU HAVE RUN OVER YOUR OPPONENT 4 TIMES WITH THIS METHOD to get the achievement. At least for me, on my 10th match, the achievement popped for me after running over my Blue guest player the FIRST time, and only getting the "Hit and Run" award. This suggests to me that the achievement description is wrong and should say: "Get the 'Hit and Run' award in 10 matches." Ultimately, this is the same solution as Maka91 (run over only once), but I wanted to give the details to hopefully save some of you fellow gamers some time, in case anyone else had the same confusion as I.