Test Drive Unlimited

The quickest and easiest way to get this achievement is to boost.

There's a race near the north-west corner of the island, at the eastern end of the air strip (you'll see it quite easily on the map). The race is called "Near Future" and is a simple, 1 mile drag race with no traffic. If you use a very fast car, such as a fully tuned Saleen S7, the race should take 20-23 seconds. Taking into account the loading times, it should take you 20 to 25 minutes to win 30 races.

I would strongly recommend that you find a boosting partner because the majority of people who still play the multiplayer races are those who are hardcore into the game and only race to be at the top of the leaderboards. As a result, there's very little chance that they're likely to let you win.

The fastest ranked race i know is "Ride in Kapahulu" - speed challenge with max speed result. One player speeds up to 150 mph, other - speeds up to 100 mph, it takes 10-20 seconds.

The fastest way to do this is to race on the drag strip towards the far north-west point. Trace the cost along the north edge until you find the race. It is a total distance of 1 mile. Make sure you have a friend. After selecting the race go to create race, ranked match, and then press A as quickly as you can to get to the ready screen. have you friend join your match and then start the race. A race takes around 35 seconds in the slowest car in the game so you should be able to do it fairly quick. If someone else keeps joining, limit the race to 2 people when you are creating it. It takes about 3 minutes to get this achievement. 30 seconds to set up the race and another 30 to complete it.