This is sorta related to the small principle in visual design, that you shouldn't actually make rounded corners by joining a straight line (of infinite radius) to an arc of a fixed radius—because things don't work that way in nature. Instead, the radius should change gradually in and out.

If only Arrow Dynamics understood that when they designed their roller coasters. Maybe they'd still be in business instead of losing to B&M and Intamin.

Here's a lovely example of Arrow: https://youtu.be/mEcQyO77p7E?t=63

Note how jarring the transitions are between elements. Meanwhile, here's a nice smooth B&M ride: https://youtu.be/6Ee3pfpo1eQ?t=86

AD seem to have been able to make the pitch flow quite alright, but dropped the ball on the roll movement. Shame—the ride per se looks exciting just from the vid.

The other problem Arrow had was the lack of heartlining. That is, the axis of rotation when banking.

For optimum comfort of the rider, when the track banks, the center of rotation should be at the rider's chest. Arrow fails to do this, and places the center of rotation between the rails. This causes any banking to create a significant lateral force on the rider, which whips the rider's head into the over-the-shoulder retraint. In a proper heartlined roll, the track appears to "slip" from under the train, like this: [0]

In the video I linked, the turnaround after the two vertical loops was particularly brutal and painful.

What makes it even worse is a poor design of the wheel assemblies. The wheels on the inside of the rail that keep the car centered are designed to allow a small gap between them and the rail, and they're not spring-loaded or dampened in any way, which causes extreme levels of hunting oscillations [0].

Their roller coaster Drachen Fire [1][2] was so rough and painful that they stopping running the ride out after only 6 years.

[0] https://rcdb.com/3475.htm#p=42548

[1] https://en.wikipedia.org/wiki/Hunting_oscillation

[2] https://youtu.be/zhtZLRZ4p8w

[3] https://rcdb.com/112.htm

That's interesting you mention Haldon Hill. They may have got the A38 bit right, but if you go up the other road, the A380, then there is a quite sharp blind right bend at the top that clearly hasn't been done right.

That's due to topography I think and probably history too. Those roads have been around for quite a long time. I don't go down the A380 very often these days but I know the the A38 between Plymouth and Exeter very well.

Holden and Telegraph hills and that area in general have roads that are millenia old or their course was generally decided quite a while back and repurposed every now and then. Starting off life as livestock drovers trails and the like. The old Britons may have cut back the trees and the like a bit. The romans did proper engineering. After them things went a bit vague for a while. etc.

Have a look at this: https://www.romanobritain.org/7-maps/map_counties_roads_town... - the Fosse Way runs "under" the A38 for quite a way and may be the A380 too, south of Isca Dumnoniorum (Exeter.) I'm now in Yeovil and the Fosse is the A37 here. The stretch from here to Ilchester (Lendiniae) is called Roman Road and is straight and flat and prone to flooding!

I think the Holden Hill roads have been done quite well. The hill is a nightmare shape! Each square metre will belong to someone, who would have to be bought out or worked around. There's a race course at the top and a fuel station, houses, and who knows what else on it. The traffic volume can be huge, especially in summer.

My mum was from Devon and her description of driving from Newton Abbot (Ipplepen) to London in the sixties is pretty ... different to now. It often took two days by the time you decided to stop after sitting in traffic for hours (now: about three hours.) She also drove to Edinburgh and beyond quite often and that really took some time. I used to commute from Plymouth to Chertsey (near enough London) and that took around four hours in the mid nineties.

Next time you drive out that way or anywhere for that matter, cast an eye on the place. See the boundaries, think of the history. In Devon, look at the depth of the hedges - its called "Devonshiring": the dense hedging "walls" with lanes running through them. Many of those hedges are bronze age or older. Modern Devon and Cornwall are roughly what was Dumnovaria (according to the Romans) which is suspiciously similar to modern Brittany and rather closer to Wales (Brythonic) than what becomes modern England eventually. The Corns wave a flag and a language that sadly was only properly native up until about 50 years ago when the last native speakers died. It is being revived and is a Brythonic language, like Welsh (Cymraeg), Scottish (Gaelic), Irish (Gaeilge) and the rest. There is also Cumbric (Cumbria) and others. Devon was largely subsumed by Wessex (West Saxons) earlier than Cornwall and hence is a bit more English (whatever that means.)

The reason that I'm wittering on about history is those roads are seriously old and have a context. Imagine who else has trod those roads back in the day. For example the patron saint of Germany is St Boniface. He's from Crediton.

> in and out and the main bend itself

How would you rate humans for doing this right, in general , everywhere they have?

Not sure I've looked at the entire world's road bends.

I do know that with a few exceptions, English roads do what the posted signs say they will do.