Cleanup is going to take awhile, so the site is back up but editing has been disabled.
Dune Buggy
From HalfLife 2 Knowledge Base
The Dune Buggy is a four-wheeled land vehicle used during the majority of Chapter 7: Highway 17. It has off-road capabilities, but cannot be driven in deep water. It is powered by a V8 engine.
It has a Tau Cannon mounted on its right side, functioning similar to its mobile predecessor in Half-Life 1. It fires laser-like beams which can optionally be charged with the secondary fire button for increased power.
Also available on the Dune Buggy is a turbo that provides a brief boost of speed. The turbo is particularly crucial in a few parts of Highway 17, when players are required to jump over damaged bridges and to avoid an oncoming Combine train. The turbo is activated when the Shift key is pressed.

