Roller coasters provide you with sensations we can’t normally feel.
There aren’t many opportunities to safely plummet towards the ground, reach stupidly
high speeds, or experience total weightlessness.
Roller coasters can take some of these sensations to the extreme - Kingda Ka plummets you 127m
418ft towards the ground; while Formula Rossa accelerates you to the top speed of 240kmh
149mph.
But, how much of this can the human body handle?
Is there a roller coaster out there that’s too much for even the bravest thrill seeker?
Put simply, no.
Roller coasters are designed to be enjoyable, though some would perhaps disagree.
Your body can only tolerate so much before it becomes uncomfortable.
Therefore, roller coasters have to adhere to strict standards which limit how intense
they can be.
These limits are measured in G-forces.
What are G-forces?
Theme parks often tout their rides as having many Gs of force.
Like Skyrush, which, according to Hersheypark, subjects you to up to 5Gs!
Cool, but what does this mean?
G-force, short for gravitational force, is a measurement of acceleration, not force - not
the best name really.
You, wherever you are currently, are experiencing the force of gravity, which pulls things towards
the centre of the earth.
If you drop an object, gravity will cause it to accelerate towards the ground at a rate
of roughly 9.81 metres per second squared - which usefully corresponds to 1 G-force,
or 1g for short.
Therefore, a roller coaster which boasts a maximum of 5Gs, 5 g-force, causes you to feel
five times the effect of gravity.
In most cases, this means you’ll feel like you’re being pushed into your seats 5 times
harder than if the ride wasn’t moving.
This sensation makes you feel heavier, almost as if the ‘new’ additional weight pins
you down.
The G-forces you experience on a roller coaster can be broken down into six key directions.
Forwards and backwards, known as linear or longitudinal acceleration, denoted by the
x-axis; left and right, known as lateral acceleration, denoted by the y-axis; and upwards and downwards,
known as vertical acceleration, denoted by the z-axis.
It’s this final direction that we most commonly associate with roller coasters.
To make things more confusing, the G-force being applied to your body is opposite in
direction to the acceleration you feel.
This is because your body has inertia, essentially meaning it doesn’t want to move.
When a roller coaster launches, the entire train accelerates forwards.
Your body doesn’t want to accelerate but is inevitably forced to, causing you to be
pushed back into your seat, as your seat pushes you forwards.
With that in mind, let’s explore the six directions of g-forces.
At the bottom of a large hill, you’ll experience what is commonly referred to as positive G-forces,
which act in the upwards direction.
These forces give you the sensation of being pushed downwards into your seat, causing you
to feel heavy.
The opposite occurs while climbing over the top of a hill at speed.
You’ll feel as if you’re being pulled upwards out of your seat, causing you to experience
weightlessness.
These types of Gs are commonly referred to as negative g-forces and act in a downwards
direction.
Linear or longitudinal g-forces accelerate or decelerate a roller coaster’s train.
On a launch coaster, you’ll be pushed back into your seat while the train accelerates
forwards.
The opposite occurs when you hit the brakes - the train decelerates and you fling forwards,
into the restraint.
And finally, lateral g-forces act from side to side.
Some roller coasters feature tight hairpin turns that drastically push you to the side.
These g-forces are less comfortable for the human body to experience, causing designers
of roller coasters to reduce their effect.
Each type of force affects the human body differently.
With training and special equipment, humans can be subject to ridiculously high g-forces
- fighter pilots regularly experience 8Gs for example!
Fortunately for you - roller coaster designers understand that not everyone is a fighter
pilot.
Rides are designed for the masses.
Their g-forces are limited to what the average person can endure.
How much force is too much?
The human body can deal with a surprising amount of g-force for short durations of time.
Our tolerance quickly declines with duration, however.
This means that a high amount of g-forces for a short duration of time could feel less
intense than a smaller amount over a longer period.
On top of this, the transition between different types of G-force can also impact a ride’s
intensity.
A quick transition to large amounts of Gs would feel stronger than a gradual increase
over a prolonged period.
With all of this in mind, various authorities around the world have placed limits on the
amount of force roller coasters can feature.
Rides in the USA are bound by the American Society for Testing and Materials, the ASTM;
while roller coasters in Europe adhere to the European Committee for Standardisation,
the CEN.
Both of these authorities place the following similar, if not identical limits on the amount
of force roller coasters can subject you to, in all six directions.
The most common g-forces found on roller coasters, positive and negative g-forces, feature distinctly
different limits.
Positive g-forces, which cause the sensation of being pressed into your seat, are limited
to a maximum of 6Gs for no longer than 1 second.
This decreases to 4Gs by 2 seconds, 3Gs by 5 seconds, and 2Gs after 12 seconds.
Interestingly, the world’s most intense roller coaster features an incredible 6.3Gs,
which according to the limits, can’t be experienced for longer than 0.2 seconds.
Roller coasters with extreme amounts of positive Gs may cause you to grey out.
During this phenomenon, the body finds it difficult to pump blood up to the head.
This leads to your field of view shrinking and becoming excessively grey.
If you’re subjected to a grey out for an extended period you may blackout and become
unconscious, known as G-LOC, G-Force induced Loss Of Consciousness.
Fortunately, once the g-forces have been removed, you’ll regain consciousness and normal vision,
with no damage done to the body.
Negative g-forces, responsible for the sensation of being lifted out of your seat, feature
much lower limits than positive g-forces.
These quickly fall from -2G after 0.2 seconds, to -1.5Gs for up to 4 seconds, before decreasing
to -1.1Gs after 7 seconds.
For context, the first airtime hill on Kondaa at Walibi Belgium subjects riders to roughly
-1Gs for about a second, before decreasing to 0Gs for a further second.Sadly, I don’t
think any roller coaster in the world has a hill big enough to reach this 7-second limit.
Ride’s with excessive negative Gs may cause your body to struggle to pump blood away from
the brain, known as a red-out.
A redout is potentially dangerous.
As a result, strict lower force limits are placed on negative Gs to make redouts impossible
on roller coasters.
Linear g-forces feature similar limits to positive and negative g-forces.
G-forces which cause you to be pinned backwards into your seat, during a launch, for example,
can reach a maximum of 6Gs for up to 1 second, 4Gs for up to 4 seconds, 3Gs for up to 11.8
seconds, and then 2.5Gs onwards.
The launch of Bluefire at Europa Park in Germany causes you to feel approximately 1G for about
a second, before slowly decreasing back to 0Gs.
The limits to linear G-forces in the opposite direction, when a train hits the brakes, for
example, depend on the type of restraint used to secure you into the train.
A heavy brake will cause you to fling forwards, which may be more comfortable with a more
restrictive over-the-shoulder-restraint, compared to a lap bar.
Beyond 0.5 seconds, lap bars restraints are limited to -1.5Gs whilst over-the-shoulder
restraints are limited to -2Gs.
Roller coasters which place you in a prone position have higher limits, up to -3.5Gs,
as they better support the body during braking.
The final brakes on Anubis the ride at Plopsaland de Panne in Belgium subjects you to just over
-1G worth of deceleration.
Lateral g-forces, which can throw you to the side, are uncomfortable for prolonged periods.
As a result, both directions are limited to 3Gs, which begins to fall towards 2Gs after
one second.
The hairpin turns on Matterhorn Blitz at Europa Park in Germany feature 1G corners, pinning
you to the side of the train.
Theoretically, in all six directions, roller coasters have no g-force limits for Gs sustained
for less than 0.2 seconds.
Despite this, on a technical basis, a ride’s maximum g-force will be limited by other factors,
and are unlikely to fall too far outside of the peak g-force limits.
All of these limits are designed to ensure the average person can ride roller coasters
comfortably and safely.
Manufacturers of roller coasters will often add additional margins to the limits to make
the ride even more suited to the average theme park goer.
Although, that doesn’t mean they can’t pack a punch.
Intimidator 305, a 305ft 93m tall giant at Kings Dominion in the United States became
infamous for its incredibly intense turn right after the huge first drop.
Upon opening in 2010, riders quickly reported greying out during the long corner, with some
even saying they blacked out completely.
This was despite the ride being designed well within the confines of the force limits.
Intimidator 305’s manufacturer, Intamin, went on to adjust the turn to reduce its intensity
and solve the issue.
Nevertheless, the ride continues to cause grey-outs even to this day.
How do roller coaster designers get it right?
Throughout the designing process, the limits set out by the ASTM and CEN are at the forefront
of roller coaster designers' minds.
They want to ensure their rides are enjoyable, and ultimately, safe.
However, there’s a lot more to designing roller coasters than just their intensity.
The amount of stress placed on the ride’s track and trains, where the supports will
be placed to deal with this stress, and obstacles in the ride’s general area must all be considered.
And, on top of all of this, the G-force exerted on roller coasters changes depending on where
you sit in the ride vehicle!
Roller coasters with longer trains create more variance in force across the ride vehicle
compared to shorter ones.
Take a traditional roller coaster drop for example.
The front of a long train slowly navigates the top of the drop while the rest of the
train climbs the lift hill.
As the train begins to fall, it builds up speed, causing the back of the train to be
pulled over the top of the drop.
On Silver Star at Europa Park in Germany, the front of the train peaks at 0.12Gs throughout
the first drop, close to near weightlessness.
This decreases to -0.05Gs for the middle seats, and -0.29Gs for the back seats.
We’ve produced a whole video which explains this weird quirk in more detail.
Essentially, the shorter the train, the more similar the ride experience will be regardless
of seating position.
https://www.youtube.com/watch?v=digOQme9aFU
So, with all this in mind, how do designers get it all right?
Well, fortunately, they have specialised software to calculate the G-forces experienced on a
ride in different positions within the train.
Unwanted G-forces, ones which could lie outside the limits, can be removed via small adjustments
to the track.
For some elements, these G-forces may occur at the front of the train, while for other
elements, they may occur at the back.
Today, specialised software can also create the “perfect” ride experience.
‘Force Vector Design’ flips the process of designing a roller coaster on its head.
Instead of designing the track and seeing the resulting G-forces, the G-forces are designed
first which the software then converts into a layout.
This removes unnecessary jolts to create smooth transitions between elements, resulting in
a ‘perfectly’ flowing ride.
This type of ride design can be found on some of the newer rides built by Vekoma, like Lech
Coaster, at Legendia in Poland.
Although rides without force vector design may feature greater variations in acceleration,
sometimes this can make them more thrilling, as manual design allows for snappier transitions
between elements.
What’s next?
So, the ride has been designed, and the track fabricated.
What happens next?
Once it’s transported to, and built at the theme park in question, the new roller coaster
is tested.
How?
With test dummies!
Accelerometers, small instruments that measure acceleration, are placed on various locations
of the train to record the amount of g-force experienced during the ride.
The placement of the accelerometers on the trains is critical.
According to European standards, they have to be placed 120cm above the seat, and 10cm
in front of the backrest, roughly corresponding to the position of the rider's hearts.
Unfortunately for those testing roller coasters, speed and thus accelerations aren’t always
consistent as you might think.
Several conditions can change a ride’s speed, including weather, the number of times the
roller coaster has already run, and how full the ride’s train is.
Additional dummies are used to simulate extra weight within the train, helping the roller
coaster to maintain its speed through the entire layout.
On top of this, rides must have at least three test runs before their G-forces can be measured,
to maintain consistency between measurements.
The readings gained from the accelerometers are highly detailed but often include unwanted
noise or vibrations.
These are removed with help of computer software, resulting in a clear indication of the roller
coaster's G-forces throughout the entire ride.
The ultimate result are these, the graphical visualisations of g-force you’ve been seeing
appear throughout this video.
They’re a fantastic way to visualise the strength and length of G-forces across all
six directions of motion.
They’re also incredibly useful for determining whether or not a ride breaks the G-force limits.
The exact G-force breakdowns of roller coasters aren’t anywhere near as common as the maximum
G-force figure many theme parks advertise.
Fortunately, there’s a group of people going around recording the G-forces of roller coasters
to a level of accuracy which often matches the official organisations.
CoasterStats are currently travelling to theme parks and correctly attaching their accelerometers
to roller coasters to demonstrate the huge range of G-forces that can be experienced
on rides.
All of the visualisations in this video have been captured by the CoasterStats team, and
these are just some of the many rides already documented.
If you’d like to know how intense your favourite ride is, check them out by clicking the i
button, or clicking the link in the description.
Conclusion So there you go, despite roller coasters getting
taller and faster, they’re never going to be too much.
Rides are designed for the masses, not fighter pilots.
The G-force limits put in place by authorities such as the ASTM and the CEN are there to
keep you safe.
Though, it’s up to roller coaster designers to continue to make rides more fun than ever.
Thank you for watching, and a huge thanks goes to CoasterStats, for helping to make this video!