JoeyBike

For you guys out there, ever find yourself cycling along and notice an attractive woman walking toward you on the sidewalk with a tree between you and her? The tree is so close to the woman that as you cycle at say 15 mph and she walks at 2 mph, the tree will STAY between you and her foiling any chance you might have for a better look. Unless of course you, or she, alter speed.

There is a scientific phenomenon where this occurs with a cyclist (the woman), a car (the man), and the front pillar post of the vehicle (the tree). Only instead of resulting in frustration it often ends in tragedy.

If you like geometry, and want to learn how to avoid crushing or getting crushed at an intersection with clear lines of sight, then this is for you. Enjoy

Collision Course: Why This Type Of Road Junction Will Keep Killing Cyclists


» Collision Course: Why This Type Of Road Junction Will Keep Killing Cyclists

KD5NRH

Is the tree transparent, or am I using some sort of towed-array hottie spotter?

There are good looking women all over the place. I'm more interested in this apparently unique tree that I can sort of see through.

JoeyBike

Funny. Tree is solid. Woman is spied far up the road briefly, then disappears behind the tree forever. Even though both people keep moving at a steady rate of speed the woman and the tree remain in "eclipse".

Ninety5rpm

Simple solution:

Kontact 

This is a problem for pedestrians as well - I see it all the time.


That said, I am now firmly anti-geometry.





I am also against molecules.

wingless

There are many decent roadway design guidelines available.

All of them specify having intersections meeting at 90°, flat, level w/ unobstructed view. As any of those deviate from that ideal, then other changes are required to maintain safety, such as decreasing speed or adding stop signs.

The linked, unimplemented modification is okay, but a better solution would be to have modified both minor roads so that both met the major roadway at 90°, with the added benefit of being offset, to ensure the vehicles on the minor road come to a stop.

wvridgerider

Too much math but a good looking woman is hard to beat

FBinNY 

This is an important and worthwhile article for anyone wanting to improve his own safety on the road. I strongly recommend that people read the original in it's entirety.

While the car's pillar is a factor, these collisions also happen at sea where there's no visual obstruction.

The reality is that humans are not good at calculating the vectors involved and predicting the future positions of themselves and crossing objects. When the speeds and angles are right a crossing object will appear to stay in the same place (angle in the field of vision) and so it's very easy to underestimate it's speed (it's not moving at all, right?) and not be aware if the risk of collision.

When you and a car are approaching an intersection at right angles, odds are that you'll under estimate it's speed, but much more important is that the driver will greatly under estimate yours, so neither of you won't make the adjustment to avoid collision.

There's not much anyone can do about this, but awareness will ensure that at least one party (you) will make the necessary adjustment, or at least be prepared to if the other party doens't do so first.

WNCGoater

What about gravity? Not only is it a good idea, it's the law!



Kidding aside, it was a very interesting article. I would surmise the strange angle is somewhat of a fluke which made this particular phenomenon particularly prevalent there. Seems it would be a simple and relatively inexpensive fix.

FBinNY 

Not at all. The problem is somewhat independent of angle, and at sea manifests at just about all crossing angles.

As an example, I was sailing on a large schooner, and we were slowly passing another sailboat that seemed to be on a parallel course. Turns out it wasn't and both crews were watching a collision in slow motion until it became obvious and we altered course at the last minute.

DrIsotope

I detest non-90ş intersections. Nearby Riverside is chock full of them.

KD5NRH

Simpler solution; when approaching an intersection where you don't have right of way, slow down. Stop if necessary. If there are obstacles blocking your view of cross traffic, move your head.

CliffordK

Oh, I can imagine the return of the bubble shaped Pacer.



Perhaps a little more work to reduce the pillars. There are quite a few cars with frameless windows on the doors, but still have the main pillars.

That is one thing I dislike about Mom's Prius, really bad rear visibility

FBinNY 

Not quite so simple. What about when you have the right of way.

Intersection accidents are usually the result of 3 incorrect assumptions.

1- I've correctly estimated the speed and position of the approaching vehicle.
2- the approaching driver has correctly estimated my course and speed
3- I have the right of way and the crossing driver will recognize that and yield

We can blame intersection design, but the fault is human, not technical. I'm sure that I'm not the only one who's come to an intersection where the crossing driver is dutifully stopped at a stop sign. Then at the last, and most inconvenient moment has decided it was a good time to proceed.

Stay alive by being ready to react not only to what drivers should do, but what they might do.

njkayaker

The collision occurred because the drivers blew the stop.

FBinNY 

It's a shame that the article focused so much on the main pillar. Has it occurred to anyone here that bicycles don't have these pillars?

While drivers were at fault here, the bicyclists contributed by relying on false assumptions about what those drivers were going to do.

FBinNY 

Assumption no.3 in my post immediately above yours.

79pmooney

I should point out that the crash in the scenario Joey is using as an example is different; it wll lead to a single vehicle crash. Cyclist will veer toward the right as he focuses all his attention to the right hoping to see that woman. This rightward veer will take him into the tree. Woman walks past unharmed.

Ben

CliffordK

True,

A basic rule of driving is to assume all the other drivers are going to do something entirely stupid. So, for example, when sitting at a stop sign, you see a car signalling a right turn. One should assume they're not going to turn until it is proven otherwise.

So, there are two cases...

1. Car never stopped, and blew the stop sign. Cyclist had right-of-way, not stop. The cyclist SHOULD have seen the car approaching and not stopping, and should have simply stopped and yielded to the car.
   However, that does require a little extra attention on the part of the cyclist. Perhaps an accident can be avoided 99 out of 100 times, but there is always that 1/100 time.
2. Car did a quick stop & go stop. These are the least predictable. Car appears to be stopped, but when one gets right in front of them, they start moving again.
   Fortunately these stop and go stops are the least lethal as speeds are often reduced, and both parties often note their error and take evasive actions before an accident occurs. This may also be the reason why the first cyclist in the article was spared serious injury.

I'm not sure the staggered intersection favored by the author is the answer. I find them to be quite annoying. Yes, they should slow traffic, and that might be worthwhile considering. Although, for a cyclist, it often means merging onto a busier street for a block or so.

I hit this one a few times a year.

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