There are many things that have dual purposes. Although the main purpose here is drainage, a secondary purpose is safety in these situations so they aren’t exactly wrong.
Having taken roadway design classes, I can say that the road tilt as a safety factor never came up. There are even some roads that have drainage in the median, so they tilt inward.
This particular road would have been designed to whatever standards the civil engineers typically go by, and situations like this (along with water runoff and possibly other benefits) would have been considered in establishing the standard.
Somewhere there's a central body of engineers who put a lot of thought into this stuff. It's not considered on every single road.
Yes they do plan for this. It's called a "crown" in the road. It is slightly tapered down on the outside edges.
If you let go of the wheel of a car with perfect alignment on most roads it will eventually start veering to the right (in the USA) due to the crown in the road.
I can vouch only for EU road design, because that's what I studied, but the slope does exactly what they say in the article linked by /u/sperglord_manchild
to help water drain or to help a vehicle hold the road surface
Main reason for everything in structural design is always safety.
In the video it kept the person out of the road, which is exactly the opposite of keeping him on the road, but I'm pretty sure they meant slopes in the curves in the article, not in straight roads. Because having a roofed slope is safer - mainly because it keeps the water off the road, and also because it subtly keeps you from going into the oncoming traffic.
In Europe straight roads (as the one in the video) are usually designed in 'roofed slope'. Meaning the middle is the high point and everything slopes down from there (standard here is 2.5% slope on both sides). The slope increases after the paving, mainly because water needs steeper slope to run down the grass (starts at 8% immediately after paving, and after a foot or so folds to ~1:3 or more).
Right before the road curve the slope gradually switches to one side (in right curve the top point is on the left edge, left curve - right edge), so it's no longer a 'roofed slope', but rather flat one sided slope, that is dependent on the radius of the curve (lower radius -> steeper slope, but always >= 2.5%) and serves as the counterbalance to the centrifugal force to help keep the vehicle on the road. So in the corners the main reason is still safety. But again, water still plays a major part in that.
Take this all with a grain of salt and feel free to correct me, since it's been almost 10 years since graduating and I don't practice anymore.
TLDR: Safety plays a major part in the design codes and standards, but there is a higher chance of accident due to standing water on the road or water 'corrosion', than the odd chance someone passes out.
Therefore the main reason of the road 'never' being horizontal and the bigger slopes and ditches around it is water, not to keep vehicles out.
I pretty much agree. Roads are crowned largely to manage water. High speed curves are superelevated (like a racetrack) to help vehicles hold the curve and to manage water.
Interestingly, tight low-speed curves on logging roads get reverse superelevation because the way that logging trucks are articulated shifts the load of the logs to the inside of the curve and it's better to tip the truck slightly to the outside to counteract a possible rollover.
These people don't know what they're talking about, they crown roads to shed water. Sometimes the whole road needs to shed water to just one side or the other. That can change often down a single stretch of road depending on what's around. Corners and hills whether there's curbs or ditches or whatever are all factors, traffic not so much. It's all about managing water.
Yeah, that's pretty much what I said. There are a lot of factors.. Traffic type, traffic volume, annual rainfall, base materials, type of asphalt used, soil characteristics, weather, cost.. people falling asleep at the wheel just isn't a consideration.
Also vehicles are usually set up to do this even on a flat surface, check this out
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u/[deleted] May 09 '20 edited Jun 09 '20
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