It's fun to smash stuff. It's also fun to push GTA IV's physics engine and realistic damage simulator to the limit, which is what you can easily do by editing handling.dat, located in \GTAIV\common\data\ inside your GTAIV installation directory.
You can grab a copy of my handling.dat file here. It changes the bus to make it 99999 kg and take no damage, as seen in the video below.
Remember, back up your original handling.dat. If GTA detects it to be different to the copy distributed with the game, it won't let you play online.
If you would like to edit other vehicles, you can open up handling.dat in your favourite text editor and edit the various values. Note that the headings are at the top of the list of vehicles. If you find the row of data responsible for the bus:
; name mass drag boy centreofmass transmission brakes steer wheel-traction suspension damage seat val mflags hflags anim [...] BUS 99999 3.0 80 0.0 0.0 -0.2 0.0 6 0.12 0.3 135.0 0.15 0.55 0.2 40.0 0.90 0.75 15.0 0.15 0.45 1.0 1.0 0.7 0.20 -0.25 0.0 0.5 0.0 0.0 0.0 0.0 0.0 400000 8 300000 2
... the headings above the row of vehicle definitions match up with the data. It's quite a convenient way of laying out the data from an end user point of view because you can read and edit it in plain text effortlessly.
A note about damage: If you set the damage value to 0.0 0.0 0.0 0.0, your vehicle will take no damage.
If you're interested in seeing more smashing and action, I have a whole set of GTA IV videos.
