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This comment avers, on What knowledge might save your life one day? : AskReddit

If you're a pedestrian and crossing a street, if you can see the sun[']s reflection on the windshield of a car, there's a good chance the driver can not see you.

Can someone please ELI5 this? I know no physics. That comment is followed by this

If your shadow points toward the car, same.

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    $\begingroup$ Sounds like it is based on that the sun must be roughly behind you relative to the driver, who presumably has a hard time seeing you because of the glare. The reflection is however tricky, since a slanted or curved windshield might allow reflection from a very different angle - this is a rough rule of thumb, not an absolute fact. $\endgroup$ – Anders Sandberg Aug 11 at 8:41
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In order for you to see an image of the Sun coming off the windshield, that means that rays therefrom must be hitting that windshield and then reflecting off in the right direction to reach your eyes.

And the fact that rays are hitting that windshield means that also, given that it is mostly transparent, some, in fact most, of those rays are being transmitted, instead of reflected. That is, the Sun is shining into the inside of the vehicle, and hence will be near or in the driver's field of vision, likely greatly interfering with their ability to see thanks to the intense light.

Of course, depending on the exact angles involved, it might still be out of hir field of vision, or sie may have a visor down to block it. Nonetheless, the point is to use the precautionary principle: since it indicates a sizeable chance that something dangerous is happening, treat that chance as 100%, and act accordingly (i.e. don't just dart out into the road expecting they'll see you and stop, but wait for them to pass and there to be a large enough opening in traffic to make it through with considerable safety margins or, better yet, look for an intersection with traffic signals).

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It depends on the conditions which the driver uses inside his vehicle. If he uses polarized glasses or lowers his visor, he might still be able to see the pedestrian since the only factor which is coming into play here is that the intensity of the sunlight from the front is very high, but insufficiently high for the driver not to drive his vehicle properly. So, there is no definite answer to this question. It depends on too many factors such as the curvature of the windshield, dimensions of the vehicle, the timing of the day etc.

Now, assuming the windshield to be perfectly plane and the driver not having any kind of visor or protective appliance, the facts that you stated above may very probably be correct.

If you see your shadow towards the driver or the reflection of the sun on the windscreen of the car, it simply implies that very intense sunlight is falling on the windscreen, intense enough to be visible at a distance. The rest depends on other factors as I have stated above.

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Windshields are slanted, so you would only see the Sun's reflection if the Sun is high above. This would not affect the driver's view.

If your shadow points toward the car then the driver is looking into the Sun, so beware.

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