# Twin headlights

Discussion in 'The Perfect Line and Other Riding Myths' started by Sparrowhawk, Jul 12, 2014.

1. ### SparrowhawkLong timer

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More excuse finding. The Road Glide Customs presented the same headlight image as an automobile 0.8 miles away. For this analysis we get into trigonometry (from the Greek trigonon, meaning "triangle" and metron, meaning "measure").

I'll use 50" as a typical distance between headlights for an automobile. The distance between the two Harley lights is 8". Two headlights 50" apart and 0.8 mile away makes a long, narrow triangle. At which point along the triangle would two lights 8" apart fall? About 0.13 mile away, or 680 feet. That means when I pulled out to pass, the Harleys were about 225 yards down the road instead of 1,410 yards, or about 105 yards past the front bumper of the leading semi. (My apologies to those more familiar with metric units. We have yet to modernize our distance units here so we still have to multiply and divide by 5,280, 12 and 3.)

To answer DesertTortoise's question " How long will it take for my passengers to see their life flash before their eyes?" With me going 90 mph and the Harleys going 75 it's about 3 Colorados before we close the gap. That is about the time I get passed the second car. My passengers better flash quickly.
2. ### anotherguyunsympathetic

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They'll probably live longer if they call a cab.
3. ### SparrowhawkLong timer

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Been awhile since you've ridden in a cab?
4. ### jgiacobbeLong timer

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I usually don't pile on this kind of thing but dude. Your math states you F'd up by not reading the situation right. You put the bikes barely in front of the Semi with your calculation. There youh ave your item to judge scale by. Let me give you a clue. Get your eyes checked again and have them tell you what you're vision actually rates as. There is a huge difference between 20/20 where you see nice clear images and 20/30 where the doc says you check out fine and don't legally need glasses to drive.

I had PRK laser surgery for nearsightedness a bit over a year ago. 3 days later they told me I was legal to drive unaided. I drove to work. Felt like I was blind. Couldn't tell you anything about cars that were more than 5 car lengths away. At work I turned all my font sizes to gia-hugic so I could work on the computer. That was 20/30 and legal to drive. Luckily it improved to 20/15 after a couple weeks. Point is, just because your doc told you you can see, you may not be able to see 20/20. That bnluriness around the edges makes a big difference. Also if it has come on gradually you are most likely not cognizant of it. As a kid when I went nearsighted, I had no idea it was my vision worsening. I just thought that teacher wrote smaller than the previous one.

Operating vehicles at high speed, especially if you are doing stuff like trying to pass 5 cars and a semi, which is stupid, requires extra super vision to make sure the way is freaking clear. There is a reason pilots have high requirements for vision.

For the OP, don't be stupid trying to pass so much at once. It is stupid. For everyone including the OP, don't take your sight for granted. Get it checked. That way if nothing else you can see the look on the faces you are going to hit head on before you do.
5. ### DesertTortoiseFreedom Fighter

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Come to think of it, I've had a few near death experiences like the OP described in a Korean taxi
6. ### Bill HarrisConfirmed Curmudgeon

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Exactly-- that is the arrangement I settled on many years ago-- a distinctive pattern, and since it is legal up front, a pattern plus a color difference.

What I ended up with in front:

As a "next step", I'm thinking of replading the daytime (H4) headlight with a ring of uber-bright white LEDs, much like on many current autos.

Rear lighting:

The two large outer tail lights are also brake lights, so the pattern keeps while braking.

One problem of the times is that nowadays many cars have required "daytime running lights" in front. Good idea, I guess. But back years ago, the only vehicles with DRLs were motorcycles, and they stood out from the crowd. Nowadays, they can blend in.

My 2c.

--Bill
7. ### SpaceKnightAdventurer

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I find it amazing that you can tell how far apart headlights are when the vehicle is .8 miles away. Wish I could see that good.:eek1

If you see a single headlight do you assume it's a motorcycle or a car really really far away?
8. ### anotherguyunsympathetic

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Since installing an HID in the Tuono I notice more people paying attention to me. It's aimed properly and not blinding. I get no high beam flashes when on low beam. When on high the road is daylight for about a mile 'cause I have three lamps. Only the main is HID the other 2 are 35 watt H7 halogen. I tread the fine line between bright and annoying but err on the side of caution. I don't wanna piss anyone off but I don't wanna be a hood ornament either.

I'll be installing some turn signals with 1157 bulbs so I can have 4 brake lamps and colored running lights up front w/o looking like crap. I ride too much to trust in others ability to pay attention.
9. ### SparrowhawkLong timer

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Not that difficult really if you're driving/riding in open country. Find a car or whatever off in the distance that produces the sight image you're thinking about. Note where it is in relation to a hill, overpass, curve, etc. then look at your odometer, and see how far you travelled when you get to that same point. Easy peasy

Lots of folks have focused on finding fault with my driving. That's OK. I never claimed to be perfect. I screwed up. It's missing the point though.

The thing is that I am a long time rider. I like motorcycles, all of them. I watch them as they go by. I look out for them.

The point is that if a motorcycle enthusiast can mistake the sight image of a twin headlight motorcycle and perceive an automobile in the distance then so can any driver. My 90 year old mother, my teenage son, the guy who had a few drinks before heading home, the young woman texting, the guy on his way to work without enough sleep, the woman who just found out her husband is cheating, and on and on.

Really, the only point is that a person can see two side by side headlights in the distance, mistake it for a car or truck much farther away, and do something thinking there is plenty of space that puts the rider at risk.

Be careful out there.
10. ### catweasel67RD04

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I'll often wait, if I'm looking to pass, until I'm positive about the distance to the vehicle coming my way, or about how much space I have to use - sometimes it means I miss a prime over-taking slot but I've had perception play tricks with me before. Better safe than sorry.

As for how I appear to oncoming traffic - well, I really don't buy the whole twin-headlight thing but that doesn't really matter because, even if I did,, it'd be the very least of our worries. I've lost count (well, OK, it's about a dozen over 20 years or so) of the amount of times cagers have "forced" me over to the side of the road because they're incapable of looking properly, or have depth perception issues, or are just wankers. It's never really been a problem because I'm aware that the vast majority of cagers are only looking for cars so I'm also aware to the possibilities when I get on a long stretch of road and see a lorry or other presumably slow moving vehicle coming my way. Sometimes a nice healthy weave fixes the problem, sometimes it doesn't but one thing's for sure, it'll happen again.

Oh, and something else before I forget - if you're riding in the late afternoon and your shadow is directly in front of you, that means the sun is behind you. The longer the shadow the, the more behind you the sun is and the higher then chance that you'll be "lost" in it. At this point headlights, on or off, won't make a blind bit of difference.
11. ### SparrowhawkLong timer

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No argument, except influencing how you appear to traffic is one of the few things you have some control over. Color, light patterns, etc.. Some situations are beyond control or predictability. http://youtu.be/lNJVG0zCpG4
12. ### SgtDusterLong timer

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Maybe but once you decide to pass 5 cars and a semi AT ONCE, you're potentially putting yourself in trouble. No matter what.
13. ### SparrowhawkLong timer

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Maybe. Having five miles of straight road with good visibility and a wide shoulder made it too tempting for this thrill seeker. I'm a bad person.
14. ### ZaethDekarBeen here awhile

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You're crazy!

I don't blame you, I have done stupid things while driving too... we all have. At least you can admit it.

On the flip side I do understand it being closer to a 15-25 mph difference between staying where you are and passing. I took i-90 from Spokane to Seattle this past week. I went ~90 MPH the whole way. A 20 mph difference over a 6 hour ride means I was 120 miles farther down the road compared to some of my family who left at the same time. I went a farther distance, was stuck in traffic, and was relaxing with a friend before my SIL made it home. There is something to be said about going quick on long trips.
15. ### catweasel67RD04

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Your depth perception is so good you can tell how far away a vehicle is on a 5 mile stretch of road eh? And how fast it's going? And what type it is?

So you claim that you can see a car 4 miles away doing 120mph and know it's gonna hit you quicker than a car at 2 miles doing 30?

I can't do that. I just see a blob. Might be it's a large blob, or possibly has a light. But that's about it. I've got no way of telling how fast it's going, especially on a straight road.

And, given this...

I'm gonna say you can't either.
16. ### SgtDusterLong timer

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Yeah, we saw how good your visibility was...

The day you'll admit you made a mistake, a big and potentially lethal one, instead of finding excuses, the road will be a lot more secure for everyone. Including yourself.

Don't misunderstand me. We all made mistakes one time or another. But if you want to learn from them, you must take them for what they are. You can analyse them but stop trying to rationalize the whole thing to find a reason "why" it wasn't really your fault so you could feel better.