Apparently Stellar Stone sent out a patch for Big Rigs fixing numerous issues. Here is a quote from Gamespot's updated review:
I always thought that the fact that the game was so bad made it fun. Going up mountains at full speed, driving outside of the geometry of the level, all of that crazy shit. Big Rigs: Over the Road Racing used a uniquely terrible game, but now it's just a generic racing game.
I don't know if this is old or not, but Gamespot's review was updated on April 2, 2010 so I'm assuming this is a new patch.