An interesting rack pinion gear system is composed of two gears. The straight or flat bar with a teeth cut in it is the rack which is snared with the normal round gear, the pinion. As the pinion rotates, it moves the rack in a straight line which explains the ability of the rack pinion gear system in changing rotary motion to linear motion.
Trains that are made to travel up sheer inclines are a certain example where a rack pinion gear system works. There is no way that the wheels on a train will grip the steel track since they are made of steel. The train can travel safely and at a speed along the track because its weight is typically enough. Even so, the train is likely to array backwards if it has to go up a sheer bank or hill, which is why to overcome this problem, this system has been added. A rack is then added to the track and a large gear wheel to the center of the train. The attachment is lowered and it snares with the rack as the train approaches a sheer hill or slope. Instead of slipping backward, the train is pulled up to the sheer slope. In Snowdonia National Park, North Wales, an example of a train using this gear system can be noticed.