How to tell if someone really has high beams on

It happens all the time: Someone is driving towards you in the opposite lane, or perhaps its on the other side of an intersection. Their headlights are so glaringly bright that it's blinding you, and you think they must have their high beams on. You want to flash them back or throw up a finger, but you aren't totally positive their high beams are on.  How can you really tell?

Here's 2 ways to tell: 
First way: Most modern cars have two low beams and high beams both located in the headlight housing on each side of the car. Low beams are always on the outside edge of the light housing, and high beams are always on the inside edge, creating a narrower, more concentrated and higher beam.
If it's bright, You shouldn't look at the headlight at night, but if you do, you will immediately notice the difference in placement on every car.  The high beams are closer to the inner edge of the headlight housings, (closer to the cars grill) and the low beams are always on the outside.


The other way to tell: Fog lights. Most cars with fog lights automatically disable them when the high beams are on. Unless you take the time to rewire it specifically, if a car has manufacturers fog lights on, the high beams / brights on likely not on.

"high beams" on Google image search bought back
 some rather unexpected results, so there is no photo.

What to do if someone has their high beams on and is driving toward you? A quick flick of your own high-beams should let the person know they are blinding everyone, but don't prolong using them.

 I have also always found that looking at the line on the shoulder is an effective way to avoid being blinded.