I'm a bit late for the party, but now with completely dead LIVE multiplayer in 2020 I've found an interesting trick to unlock this achievement.
Despite the achievement description says that you have to earn a Cautious rating via LIVE, it's actually works in LAN play. More to say - you can even do this with youself without using dummy accounts! Although you will need a second device (another PC or laptop) with the game installed.
Also, this offline/LAN trick could be used to unlock some other achievements:
The Cheeze It! achievement in DiRT 3 (GFWL) worth 49 pointsBe the mouse in a Cat n Mouse game where your team has gone on to win the game (Jam Session) The Join the Party achievement in DiRT 3 (GFWL) worth 129 pointsWin a game in each of the multiplayer party modes (Pro Tour or Jam Session) The Road Trip achievement in DiRT 3 (GFWL) worth 64 pointsComplete a Joyride online with at least 3 other players 1. Firstly, start the game on
your second device. You can log in to your LIVE profile on it, or even not log in at all, just start a new game without saving!
If you choose
to not to log in, then jump to number
4. In the case of
logging in to your profile - activate the game with your key if needed. Don't worry, the key has unlimited activations. Continue with number
2.
2. Disconnect network cable/disable wireless on that device. You will see the message saying that you've disconnected from LIVE.
3. After you've seen this message connect network cable/wireless back, but
don't reconnect to LIVE!
4. Launch the game on your main device, log in to your LIVE profile.
5. Go to the
Multiplayer -> Local Network -> Create Game6. Choose Rallycross, Location: L.A. Coliseum, Vermont Avenue, 1 lap, collisions ON. In advanced options
enable Impact Rating,
disable Assists,
set Damage to Full.
7. Go to the
Multiplayer -> Local Network -> Quick Session on the second device that is offline from LIVE now. LAN play will still be available.
8. On the download ghosts prompt press
NO.
Then you'll see both of your profiles with the same name appear in lobby. Impact ratings are showed near the players' names. They could be red circle, yellow circle, green circle and white hexagon. Start a game and complete the track 5-7 times, without touching or crashing into anything. You have to repeat this until you'll see a white hexagon icon on your name. Achievement will pop at the next loading screens.
And now the most interesting thing. You can also suddenly unlock this achievement while being offline on your second device (if you've logged in), and get it unlocked without timestamp. No worries - just don't go online from that device until you unlock this achievement on your main (online) device. Your online timestamp will be uploaded to LIVE servers and will never be overwritten if you ever go online from that offline device again.