@Wheely - the cars are manually driven and thus to hack them you will have to actually plug a universal cable to the car. Might be kind of tricky with people inside the cars. You can tell that the cars are clearly not slaved to the RCC. (but you are unsure what IS slaved to the RCC.)
If you still wish to try then:
Your first attempt to place two mark fails (and the RCC places a mark on your device, the second attempt for the third mark succeeds.
RCC defense:
2#7d6t5 2 2so at the end of your exploit