You may have used that free terrain flattening script from SL that creates flat spots in terrain for buildings. This Bulldozer can do that, plus much more! First of all, it can create flat areas that are tilted at angles, not just horizontal flat areas. You can re-size the prim to flatten small or large areas with a single click. Use the build tools to slide the prim to a new position and click on it to raise (or lower) terrain to continue the current tilt angle. This can be used to make ramps, river beds, cut road beds and other shapes.
Sit on the prim and use the arrow keys to start it moving. It starts out moving in its local +X direction, so it can make long straight road beds. While sitting on it, you can turn it with the arrow keys, bank left and right to create banked turns, pitch the prim up and down to change the slope in the direction of motion. This scripted prim can modify (or mess up if you are not careful) a large amount of terrain in a very short time. So like a RL bulldozer it moves very slowly (2 meters per second) and turns very slowly. If you need to turn sharply, stop the forward motion, turn in place, then start the motion up again.
For example, set the bulldozer prim sideways along the base of a mountain. Pitch it up at 10 degrees and bank it slightly down on the side towards the mountain. Jump on it, start it moving. Turn it with the arrow keys to keep it buried half way in the terrain. Drive a spiral path around and around the mountain until you get to the top. This will create a gently sloping road to drive up your mountain. (For a mountain to try this out on, check out my fractal island terrain height maps).
The original version was just a square prim that you sat on and drove around. But this works so much like carving terrain with a bulldozer that I found a mesh bulldozer and attached it to the working prim! Now you can look like you are using earth moving equipment while you edit your terrain! This is fun but actually not as practical as the single prim version. The working prim is invisible under the bulldozer and is fixed at 6x6 meters. The bulldozer has a lot of land impact for no practical purpose, but it is a lot of fun to drive around! Terraforming has become fun instead of a chore!
This scripted object works on OpenSim 0.9 or 0.8, but it REQUIRES Owner permissions, Estate Manager and Threat Level HIGH. Test for these with the Terrain Test Prim which is available free in my Kitely world Fractalis. You can hypergrid there with this address: grid.kitely.com:8002:Fractalis . The full perm script from the test prim is available here. Or you can buy the Test Prim ready to go from the Kitely Market here for a small price.
The Terrain Test script also checks for a common OpenSim bug: On OpenSim regions hosted on Microsoft servers, some innocuous script calls take up to 10000 times longer to run! The result of this is that it takes hours to generate terrain on a large var on a Microsoft Server, when it takes under 2 minutes on a Linux server. The Test Terrain prim will turn yellow to warn you about this if you are running on a Microsoft Server.