Innovation and experimentation are what drives the theme park industry forward. Most new rides are based on proven concepts, but every now and then a manufacturer or park operator will invest in something truly unique. Sometimes, the risk pays off handsomely - look at Harry Potter and the Forbidden Journey at Universal's Islands of Adventure, for example.

On other occasions, the gamble backfires. There have been numerous instances over the years of rides and attractions that have failed to function as expected, or that didn't capture the public's imagination. Let's take a look at five examples...

5. Pipeline Roller Coaster

Back in the early 1990s, the once-mighty Arrow Dynamics was on the verge of bankruptcy. However, it hoped that its salvation would come in the form of the pipeline coaster, a new design that it was showing off to various theme park operators. Chief among those was the Tussauds Group, which had just acquired Alton Towers in the UK and was looking for a unique new roller coaster to boost its line-up.

The chief innovation of the pipeline coaster (and the one from which it derived its name) was the positioning of the ride’s trains. Rather than sitting on top of the track (as with a traditional coaster) or beneath it (as with a suspended or inverted coaster), the vehicles would instead sit in-between the rails. The u-shaped track, with the trains running down the middle of it, had the appearance of a pipeline.

According to Arrow, the early test runs of the pipeline coaster were a huge success. “Awesome”, “smooth” and “totally different” were among the superlatives apparently thrown at the new creation by those lucky enough to try it out.

Problems, though, began to emerge when Tussauds' John Wardley was invited to Utah to ride the prototype. He found it to be a huge disappointment, later describing it as “very slow and rather boring”. The primary issue was the level of friction generated by the ride’s trains as they traversed the track, which made it very energy inefficient. Alton Towers chosen to build a Bolliger & Mabillard inverted roller coaster instead - and Arrow never succeeded in selling one of its pipeline coasters. The company went bust, and was eventually acquired by S&S.

4. Flying Saucers (Disneyland)

The futuristic Flying Saucers ride was installed in Tomorrowland at Disneyland in 1961, having been manufactured by longtime Disney partner Arrow Development and National Research Associates. Like a large-scale version of air hockey, it saw guests boarding personal flying saucers that sat on a cushion of air, and then bouncing into each, bumper cars-style. There was no steering wheel, instead guests simply leaned from side to side to try and guide their saucer.

Unfortunately, the Flying Saucers proved to be troublesome and expensive to maintain. This, coupled with the ride's low capacity, meant that they were scrapped in 1966 as Tomorrowland was converted into New Tomorrowland. A similar attraction, Luigi's Flying Tires, opened at Disney California Adventure in 2012.