For more than the last 50 years, nearly every roller coaster built has had a safety mechanism to make sure trains are physically locked onto the track. This is usually accomplished by "upstop wheels," small wheels that sit beneath the track. Gold Rusher is tame, and lacks any airtime, negative g-forces, or inversions, so it doesn't require wheels under the rails. Small metal pads situated under the "drive wheels" ensure that the cars will stay attached to the track.
The chain is installed to make sure the empty train doesn't roll away.
©2016 Joel A. Rogers.