In RollerCoaster Tycoon, do vehicle crashes always have a probability of occurring?

Question

I was playing the scenario White Water Park (also known as Aqua Park), which starts off with a water slide, among other rides, already in place. I know water slides are among the rides that have to be carefully designed so that no guest is sent to an early grave thanks to a sharp turn, or by hitting a small incline at too great a speed!

During this playthrough, I made no attempt to change the water slide's track or operations in any way, and for two years it did not crash. On the third year however, one (and only one) of the dinghies crashed. The crash was far from the station and it exploded off-track, so it was not due to a brakes failure (if water slides can even suffer that particular breakdown). Of the guests remaining on the ride, they all completed the circuit and exited without issue.

From testing rides before, I know that trains with guests on-board can move slightly faster than those without, but the ride had been running with guests on-board for years without a problem. In cases of 'crashable' rides, is there always an element of probability involved in whether vehicles might crash under certain conditions? Is there anything outside of the ride and guests that can somehow alter the speed of a vehicle?

The crash occurred in the original PC version, with all official add-ons available.

Answer 1

Without looking at the specific ride in question, there are a few possible causes:

Guest weight variation

There is some variation in the weight of a guest. It is possible to create a dinghy ride that 'almost crashes' with two average guests, where it will crash if two fat enough peeps happen to share a boat.

You can prevent this type of crash by making sure that sections with strong lateral Gs and negative Gs use covered pipes.

Note: The same underlying cause can cause boats to bump into eachother if you have a slide with relatively high ride duration and/or relatively short minimum time between two dinghies leaving the station. This type of crash usually involves two or more dinghies crashing into eachother though¹.

Safety cut-out

This particular breakdown stops the lift hill from working. If a dinghy is right at the top of the lift hill when the breakdown happens, it can stop right at the cusp of the hill. When the ride starts up again, this dinghy will start with a speed of 0 km/h, instead of starting with the speed of the lift hill (usually 8 km/h or 5 mph).

This may cause this one dinghy to not be able to complete the circuit, reversing, and flying off the track in reverse.

You can prevent this type of crash by making sure that the dinghies dont go very slowly at any point except for the lift hill and the station.

Long downward slope bug

Any drop with more than one steep downward slope may sometimes cause crashes, according to the RCT wiki.

That same wiki notes that this particular dinghy ride does have a tendency to crash.

¹: What usually happens here is that dinghy #2, filled with heavier guests thus going faster, catches up to #1 and bumps into #1 on the top of a hill in the track, transferring its momentum to it. This usually happens near the top of a hill as the dinghies are moving slowest, so the distance between them is smallest there. Dinghy #2 will then slide back down into the preceding valley. Dinghy #3 can then hit #2 at high speed as it's travelling fast in the valley, at which point both will explode.