How to get the “Well Informed” Achievement in Cities : Skylines

I believe you need to play through the entire game without shooting anyone to gain this achievement. If you mess up, you can reload your last checkpoint and go again but if you've passed another checkpoint since, you'll need to restart.

If you want to check as you go along, you can press the "Back" button and in the top-right of the screen it should say: "So far, you have not fired a shot at anyone". If you think you may have shot someone, hit the "Back" button and check this. If it's gone, you need to reload your last checkpoint. If it's there, you're good.

The bit with the convoy doesn't count as a shot and you can actually shoot guns in the game (at servers etc), as long as you don't shoot at anyone.

I'm copying the below quote from this link

Under Options on the main menu there is a new area called Extras. Under Extras you will find Statistics which is what you need to view to get this trophy. To obtain all of the stats you must race on every track, yes all 24 tracks, and fire and absorb every weapon. You will notice that is shows your progress on Arcade Perfect on the first page, don't worry you don't have to earn Arcade Perfect to get Stats Life. UPDATE: You must do a split screen race on any track as well. If you don't have two controllers you can use either a Guitar Hero guitar or your PS3 DVD remote, just set the remote to controller 2.

If you follow a link, the author makes a special note about the split screen race being necessary. See if that helps.