Test Drive Unlimited 2

This solution is for if you want to boost this in a single event

Set up a follow the leader match and invite a friend who also needs the achievement

Choose your fastest or favourite car and begin the event(you could take note of the milage if you want to track your progress)

Now when the event begins the leader does not drive through the 1st checkpoint,go anywhere else and just keep driving,the other player is free to go wherever they like,

As long as the leader doesn't drive through the checkpoint the event will last for as long as you want it to allowing both players to drive the 93 miles (150 km) in one go.The achievement will pop while your driving as soon as you hit 93 miles,

When both players have the achievement simply quit the event

Notes:You may want to do a keep your distance event 1st if you haven't done one before as i can't yet confirm whether this achievement requires you to play both modes or not

Don't select the event on that island at the south of hawaii or the leader will be stuck on there as the checkpoint is on the bridge out

This could get boring so try finding places you've been without being able to access the map,drive some undiscovered roads or try driving miles apart then find each other (again pretty tough as you can't open map) should help relieve the boredom

Good luck

It's total. You don't need to drive 2x150 km/93 miles. I got it after 150 km in Keep your Distance with 1 friend races.
Races can be done in private session with 2 players and it's fastest way since driven distance is added to score ONLY when all players from convoy drove within given distance and keeping all in order can be hard with 8 player race :-).

Yes, it's cumulative, as said above, however instead of doing it on Keep Your Distance, find a Follow The Leader lobby and stay in it until the cheevo pops up, that's how I got it.