More common in Yellowstone during winter than the rustic 1950's Bombardier Snowcoach are common passenger vans with a MATTRACKS conversion. MATTRACKS replaces a 4x4 wheels with a rubber track allowing the vehicle to travel over the snow during Yellowstone's harsh winters. After winter the wheels can be returned to the 4x4 and it is once again a standard passenger van allowing use year round. While slower and less memorable than a Bombardier Snowcoach, I found the MATTRACKS equipped vehicles to be quieter and more comfortable.