Have you ever seen a red reflector mounted between the rails of a roller coaster? (If you look carefully, one is partially visible on the bottom of this picture.) These are part of a sophisticated system used to measure the g-forces on roller coasters. During testing, accelerometers are mounted in the car and record both vertical and lateral g's as the train goes through the entire ride. A light is also mounted underneath the car and records when it passes over a reflector. This enables engineers to determine where the train is on the course during a data run.
I am surprised that Woodstock's Express, an old coaster and a tame coaster, recently required such accurate testing. I guess that proves that amusement parks are very careful to make sure that rides don't subject people to unsafe g-forces.
©2014 by Joel A. Rogers