Been on a few of those growing up. Never that fast.
Go Pro-style footage from a single-pipe alpine coaster in Mieders, Austria. You reach the summit via a cable car and then sit on a small car with a brake lever and off you go. Having ridden it once using a little braking, I decided to try it a second time without using the brakes.
Here is the off-ride footage.
How about one of those for the Olympic Peninsula? Low-impact, cheap to build, lots of fun and great attraction?