Roller Coaster Safety Series – Part 1: Block Sections

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Roller coasters are a great source of fun. Theme parks and roller coaster manufacturers keep pushing boundaries to offer thrilling and unforgettable ride experiences to their visitors. Sadly, lots of people still cope with fear of roller coasters. They are genuinely afraid of heights and speeds or they just don’t trust the overall safety of these rides. In our safety series, we’d like to elaborate more on a few important safety aspects of roller coasters to make you feel more at ease during your next ride. This post is all about block sections. Buckle up!

Let’s start off with a short history lesson. We can track the history of roller coasters all the way back to Russia, where sleds (and later wheeled carts) were pushed off snowy hills, often supported by wooden structures. Hence the French name for roller coasters: Montagnes Russes (Russian mountains). There’s no complex technology being used here. No lift hills, no launches, no break runs. Fast forward to modern times, where roller coasters have become highly complex and innovative machines due to technological evolutions and the growing popularity of theme parks and their coasters. These days, parks have to take three things into consideration when building a roller coaster: safety, amusement and capacity. They would want to offer an amusing and thrilling capacity to as much visitors as possible in the safest way possible. Talk about a challenge! Here’s where block sections come into play.

block sections
It’s a huge technical challenge for coasters like Taron to manage 4 trains and create a throughput of 1.200 riders per hour in a safe way!

A block section is a section of a roller coaster’s track, preceded by a control mechanism capable of stopping trains. Only one train is allowed into each block section at a time, preventing them from colliding into each other. Every coaster which operates more than one train use this system. You see, failures happen. Both machines and human beings can produce errors. If a train looses one of its wheels, the train behind it needs to be stopped before it crashes into the first one. The block system thus ensures the safest rides with the highest throughput of riders.

Let’s step aside for a second. You might be interested to learn that this system of block sections is not only applied to roller coasters. Railway transportation uses the same principles as well! Generally the entire railway network of a country is divided in sections in which only one train can travel at any given time. Once a train starts moving, it automatically demarcates a zone for itself. Other trains wanting to enter that section will be halted by a red light. Ofcourse the difference between roller coasters and trains is that trains often travel in both directions. To prohibit two trains for running into each other head on, the direction in which one train is moving will be automatically closed for trains coming from that direction. Last but not least, when something doesn’t work as it should, all lights in close proximity will automatically turn to red until the error is found and fixed. Sounds an awful lot like blocking systems!

Alright. So far we’ve talked about the definition of block sections and made a little detour to illustrate its use in railway transportation. Let’s go back to roller coasters with an example: Python at De Efteling (NL)! Python is a pretty straight-forward coaster: it features a lift hill, drop, two loopings, a turnaround, two corkscrews, a helix and a brake run. The image below illustrates Python’s three block sections.

Block Sections

Python’s first block section starts at the end of the station and ends at the top of the lift. The second section starts when the chain disconnects and extends to the brakes just before the station. These brakes should be able to stop the train if the other operating train has not cleared the station yet (which is always the case with Python as it’s a short coaster). The third and last block extends until the end of the station. Sensors can detect which block section the trains are on. However, when transitioning from block one to block two, for example, the train will be in two blocks at once. That’s why Python has three blocks but only two trains to guarantee safe operations. In general, there will be one less train on a roller coaster than the number of block section the track has. Simple, right?

This entire system needs to function perfectly. It therefore relies on a computer system (PLC or Programmable Logic Computer) which makes decisions based on inputs coming from the ride’s sensors. The PLC then communicates with the controllable start and end points of each block: should the breaks be open or closed? Can the train be released from the lift or should it wait for a second?

To detect the position and movement on each train, roller coasters depend on a series on sensors. There are a few different types of sensors but you’ll mostly notice green-ish boxes on different parts of the track. These proxy switches are electromagnetic devices that detect small little plates (often called flags) mounted to the bottom of each coach when the trains are passing by. Try to spot a few of those switches when you’re riding your next roller coaster!

Block Sections
By WillMcC at English Wikipedia, CC BY 3.0

Safety systems such as block sections make roller coasters immensely safe. The sensors can even be too sensitive, causing a roller coaster to stop on the lift or break section without a real risk or threat. For example, in the case of photo eye detectors (a system relying on a the reflection of light beams), a leaf can disturb the sensor’s signal and make the ride stop. Riders then have to be evacuated and the ride has to be inspected to see what caused the warning signal when, in reality, there’s nothing to worry about. Media tend to blow this situation up to ridiculous proportions but, as you now know, there’s almost never really an alarming error or danger happening. The slightest uncertainty makes the ride stop. There’s a reason why the chance of dying in a roller coaster is only about one in 24 million

Sadly though, when a rare accident occurs, it is caused by block violations. The accident with The Smiler in Alton Towers (UK), for example, happened because engineers working on the ride after a small malfunction didn’t know ride staff had placed another train on the tracks. They decided to overrule the block system because they could see four trains when, in reality, also a fifth train was on the tracks. This led to an awful crash and left a number of riders seriously injured. Sounds scary (and it is), but a simple visual check of the entire track could’ve prevented this from happening. Never overrule the mighty block system if you’re not 200% sure where all trains are. Don’t let this scare you though. I can’t repeat it enough: riding a roller coaster is still much (much, much) more safe than, say, driving to work each day.

That’s it for this piece about block systems! Up next in our safety series: roller coaster restraint types.

I'm a twenty-something living in Bruges, Belgium. I have an obsession for football, working and roller coasters. My fav? Twisted Colossus (Six Flags Great Adventure, California)!

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