What is Rigs of Rods?

Rigs of Rods is an off-road truck simulation game. It is based on a specific physics engine called Beam.
Beam simulates a network of interconnected nodes (forming the chassis and the wheels) and gives the ability to simulate deformable objects.
With this engine, trucks flex and wheels deform as you ride the terrain, which is based on real terrain elevation data.
A closed-source, free beta version will be available soon.