Comment by FinnKuhn
5 months ago
This doesn't look unsafe though, just inconvenient.
Both in the US[1] and UK[2] you can find bridges with actual 90-degree angles. The one in India[3] is more like 75 degrees.
[1]https://maps.app.goo.gl/3CBqVHbVEtonHjcr9 [2]https://maps.app.goo.gl/8cVB44VDJRPadY6s6 [3]https://maps.app.goo.gl/ikPSmLEGYwVJLqDz7
Those are not the same at all.
Search for "swept path analysis" for just one component of what you're missing. (There are many other components of design of a curve like this to consider.)
A 90 degree change in direction is fine by itself provided there is sufficient radius for vehicles to make the turn at the design speed.
In this case, if its two lane you may not be so convinced of its safety when it's your loved one on a scooter who got hit by a bus which tracked over into the oncoming lane just to navigate the curve. Or if its a single lane, when they died on the ambulance which was stuck in traffic on the bridge because two vehicles are unable to pass and everyone behind them would need to backup in unison to sort out the resulting cluster.
But safety is only part of the duty to the public here. The bridge needs to function for its intended specification and if it fails to do so for basic engineering reasons, you absolutely have no business holding a license and signing off on public plans and indeed you would be disciplined or stripped of your license for something like this.
An elegant solution to this problem would be to enforce a very low speed limit entering the turn.
“Sharp turn ahead, reduce speed to 5 km/h”
Completely ignoring that the point of the bridge was to move a fuckton of traffic and saddling it with a restriction that makes it unfit for purpose if the users behave lawfully is not elegant. It is ignorant to the point of not being distinct from malice. It's like an adult version of one sibling being told don't touch the other and then they get in the others face while saying "I'm not touching you".
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Even if the swept path issues were not an issue here, that method has been tried and tested, doesn't work, and is considered bad design practice in the field of traffic engineering.
There's a great deal of evidenced backed engineering practices and solutions to draw from to solve issues like this. Unlike software in noncritical applications, you can't just pull things out of a hat and hope it works. People die if you do that.
You can't just say "here's how fast you can drive this road." You have to design the features of a road to calm traffic. If you design a road like a freeway and then put up a 15mph speed limit sign, people aren't going to just drive 15mph. Thats just not how traffic and people work. If you want people to go slower you should design traffic calming features into the road.
Its generally bad to have inconsistent design speed for different features of a road. And by bad I mean people will get killed at disproportionate rates. It happens all the time anyway for various reasons but not very often.
I am curious, how did you find those?
I like to think that it's (posh accent) "Yes good sir, I do indeed keep an extensive collections of references to exotic bridge layouts"
What would be neatest is to learn that there is an exotic geospatual query language. "no junction and road bend radius less than 20M within 50 meters of bridge"
But I suspect it is a well formulated web search "Complaints about right angle overpass"
And final thoughts, Your right, it is not much different than a common freeway offramp system. So I am not sure what the fuss is about. Perhaps too constrained, and it needs a larger turning area?
I just remembered that I saw a Reddit thread with some users posting other examples of this so I just clicked on the most upvoted post for this bridge and filtered the comments to those linking to Google Maps.
So sadly there was no exotic geospatual query language involved - although that would have been a way cooler answer. :/
in the 90s i built a webinterface for a database of architectural details for a university department. i don't know if it included bridges, but i am sure that some university departments teaching bridge building or traffic planning somewhere have a database of bridge layouts. maybe this one here: https://urbannext.net/
The first one looks much safer on streetview, the road bends at 90 degrees but the lanes are curved with plenty of room between the edges and barriers on the edges too. The bridge here looks like a one laner with barely enough room to turn and barriers small enough that you could fly off the bridge.
The second link is in Canada.
"New Westminster, British Columbia" lol. It looked nothing like the UK but at least they didn't plump for Colombia!
Anyway, here is a real British one:
https://maps.app.goo.gl/VAdfguBXNcDB74Yu5
I don't think it's that uncommon especially when crossing rivers because roads typically run along the river bank. A lot of roads and field boundaries were set down 1000s of years ago.
The British way is that so long as you put up big 'ol black and white arrows then 90° is child's play, it could be a 180° hairpin. I don't drive much but I hated multi-story-car-park-spiral ramps that for four floors would be a 1560° turn at full lock in a small car. Feels like I am failing astronaut training as my stomach turns over.
There's been a bridge there since the 13th century, and the current bridge is a listed structure built 1857. It's not really something you'd choose to build today.
That is my mistake, very sorry for that. Apparently that changed all the way back in 1867. Oops.
Lmao that quayside bike lane is diabolical. Suicidal.