# Too Much Rear Light?



## m85476585 (Jun 7, 2007)

I recently rode from where I live to the Silver Comet Trail, a 90 mile MUP that's nearly flat and runs from Atlanta into Alabama. I want to start doing longer rides and the trail is an ideal place to do that. But the ride getting there is awful. It's about 10 miles from where I live, but the only roads that go there are 45mph with 2 lanes each way (so traffic does 50-55) and no shoulder. There's a 1/2 mile long bike lane in one section that ends as abruptly as it starts. I've spent some time looking and I really can't find a better route because there are train tracks, a river, and a major interstate that interrupt smaller roads. (edit: I just checked, and there are a total of six roads and four interstates that cross this 20 mile section of the Chattahoochee river in the direction I need to go, and all the roads are major arteries.) On my trip there and back I was nearly run off the road twice, once by an eighteen wheeler. Both cases I was about 1/3 of a lane width from the right, but I guess I should have just taken the center of the lane. To make things worse, no one ever bikes on these roads, so cars aren't expecting bikes.

For my rear light I was using a Superflash Turbo and the little 2 LED Reelight dyno light I have one the wheels, and I think that may not be enough. I plan on making my own light to be as attention-getting as possible. I'm envisioning four or five clusters of superbright LEDs that would flash rapidly, like the brake lights on a bus that flash quickly a few times before staying on. I would guess the flashing is at about 10-20hz. Probably a bit faster than the two small LEDs on a regular Superflash. The idea is that the fast flashing is perceived as motion, so the light is very easily noticed in observer's peripheral vision.

So I'm wondering if it's possible for my lights to be too distracting? The idea isn't to blind people, just to make myself visible as early as possible and from as far a distance as possible. Does anyone here have experience riding with an excessive number of flashing rear lights? Any tips for riding on this kind of road?


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## nov0798 (Nov 27, 2005)

I would think that amber/yellow leds would be better as that is the universal color for caution, where red is danger/stop. Just a thought!


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## sean salach (Sep 15, 2007)

Too attention-getting will cause target fixation. Your goal should be to get them to notice you, not to blind them or get them to stare at you.


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## mtbxplorer (Dec 25, 2009)

Was this in the dark or the daylight? If it was daylight, it may be more effective to fluorescent green jacket, or safety vest. If you use a backpack, add a safety triangle (by aardvark).


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## BeastRider (Oct 20, 2011)

Grainger has available a flashing GREEN led light that you might want to look into. Relative cheap and they ship rather quickly!!!!!
Five-LED Green Flashing Light, for Bikes - Bicycles - Carts and Trucks - 5DNH1 : Grainger Industrial Supply


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## BrianMc (Jan 5, 2010)

Dealing with helping drivers who are not expecting a cyclist and who are inattentive is a pet project of mine aka 'survival'.  This is not an easy answer when you have to vie for driver's attention.

Check out this thread, this thread, and this thread for some options.

In sunlight, a bright traffic yellow-green top or an ANSI vest beats all but high power headlamps. You can see that in my daytime video in those threads. In shadows of buildings or trees, riding in overcast, or other slight reductions in ambient light, a powerful tail light is about a tie, under lower light conditions the tail light pulls ahead.

The amount of tail light to be really effective in the day is much higher than for night. Most blinkies don't allow adjustment of levels on flash or rates. A series of discussions of tail light issues are in this long thread.

The Planet Bike Turbo, PDW Radbot 1000 and Danger Zones and my DIY lights seemed to make drivers look at me rather than the road ahead when passing and so they drift towards me.

The Red Zone 4 is a wide angle light of about car brake light brightness on the two highest power flash settings, has several flash modes for different rates, and 5 power levels of flash. The wide angle handy for cross traffic and curvy/hilly roads and taller vehicles. I am planning a day light test today to see what distance it attracts attention (versus being visible). Two of these at 45 degrees got my best response I have had from drivers while riding a shoulder of a 55 mph highway. YMMV

The Cygolite HotShot is adjustable for flash speed or power level on steady. It is a narrow 10 degree beam so needs to be aimed straight back and up at 5 to 10 degrees to reach truck cabs when closer. At a car length, the hot spot of the beam is only about 40 inches across, covering the lane at about 2 car lengths. It has a wider spill beam but that won't be too useful in daylight. I haven't ridden with it yet. Video coming.

I am hoping the pairing of the Red Zone 4 and a Hot Shot will be a winning combination. Maybe *mechbgon* will chime in, as he recently added the HotShot to his setup.

BrianMc


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## woodway (Dec 27, 2005)

This is an aside, but some Interstates are open to bicycles, and they tend to have very wide shoulders. Maybe not the most pleasant roads to ride on, but may be safer than a two-lane arterial that has no shoulder, at least for parts of your ride. Check with you state DOT to see if bikes are allowed. Here in Washington State, bikes are allowed on Interstates outside of major metro areas.


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## WR304 (Jul 9, 2004)

Some rear lights to consider would be the Cateye TL-LD1100 or Cateye TL-LD610. The TL-LD1100 would be the one to go for if you really want to show up. It's in a different league to the small LED lights that you can get.

Have a look at the reviews here:

Wiggle | Cateye TL-LD1100 LED Rear Light Rear Lights

Wiggle | Cateye TL-LD610 LED Rear Light Rear Lights

I have a TL-LD610 fitted to my mountain bike for riding on the road in bad weather and that's very bright, even in daytime. I use it in solid light mode. Whenever I see other cyclists with their rear LED lights set to flashing the lights never really seem to stand out that well.

Something to consider with LED rear lights is that they're directional. An LED light that shows up well when you're looking directly into it will only be a soft glow if viewed from an offset angle. Lorries in particular might not see an LED rear light because it isn't angled towards their cab. I'd suggest standing your bike outside at night and then have a look at how well your bike's rear lights show up looking at them from a car height eye view.

Pictured below: Cateye TL-LD1100 rear light has two banks of LEDs and shows up well at night.


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## m85476585 (Jun 7, 2007)

It's mostly daytime visibility that I'm concerned with, since at night I don't usually venture very far and I'm somewhat used to dealing with city traffic and city drivers are more likely to expect a bike. Like I said, the idea isn't to blind drivers, but to be as visible as possible. At the same time I want to avoid attracting too much attention and having drivers fixate on me (causing them to drift closer).

I can design something with as much power as needed, and if I run everything from a microcontroller it will be easy enough to tone it down at night. They make high power LEDs similar to white ones used for headlamps in any common colors, like this 7 watt red star:
Red 3-Up EndorStar - LEDSupply.com
Of course, superbright LEDs are cheaper and simpler do drive, so I'll probably stick to those. I can also get something in between, basically a discrete package with multiple LED dies in it but without the special drive requirements of a high power LED. In terms of angle I can do anything from a laser focused on driver's retinas to a wide angle 120 degree beam, and I'm guessing wider is better as long as it's still visible. My bike is set up for commuting, so I don't care about weight or size. I have a basket on the back, so there's plenty of space to work with.

One idea I had is an array of LEDs that appears to expand, giving the illusion that something is moving towards the driver. I was thinking red for the same reason: to indicate that I'm moving slow or might require the driver to use the brakes, and people are more used to reacting to red lights in the way I need them to (slow down or go around). Whatever the light is, the goal is to get drivers attention so they see me, then get them to recognize that I'm a bike (or something going slow) so they can safely pass or avoid me.

I know when I'm driving if I see a blinkie light in the distance, especially at night, I usually see quickly it but it may take me a few seconds to figure out what it is or where on the road it is. The problem with a single blinkie is that it's impossible to judge distance to it if it's beyond the range stereo depth perception works at, which is up to 10 meters according to Wikipedia. Beyond that the brain uses clues like size and perspective which don't work well for single points of light. There's an interesting article here
Longleaf Bicycles: How the Brain Works and Bicycle Visibility
on how people are conditioned to look for cars when they are driving, so it might help to appear like a car in some way. Ideally I would have a wide bar to give people a standard size based distance reference, but that would quickly get impractical and might add a lot of drag. I'd rather limit lights to the width to the back of the basket if possible.

I will definitely get a high visibility vest. I found a class 3 (intended for 55mph+ traffic) one here for $12:
ANSI Class 3 COOL MESH Safety Vest
The site has other cool stuff, like high-viz moisture wicking T-shirts and gloves with turn signal arrows on the back and a stop sign on the palm. I think I'll also get a reflective slow vehicle triangle.

woodway, these are interstates coming into downtown Atlanta, so bikes are not allowed and even if they were riding on them would be suicidal. I would definitely take the wide shoulder of a rural interstate if that was an option. I asked around and found one of the roads that's a little better that adds 3 miles. It's the same kind of road as the one I was on, but it's a "bike route" (whatever that is. It definitely doesn't mean it has a bike lane or that it's really all that suitable for bikes) so cars might be more likely to have seen bikes there before, and it goes through a commercial area instead of an industrial one so people are more likely to be expecting slow moving traffic in the right lane with people going to and from Starbucks and whatever. As opposed to the road I was on that was more of a means to get from point A to point B with no reason to stop in between. Along that road I passed a landfill, a large coal fired power plant with a facility that appears to process the coal, a sewage treatment plant that smells like poop, and a rail yard, among other things.


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## BrianMc (Jan 5, 2010)

Testing the narrow 10 degree beam 2 W HotSHot with the 180 Degree 4 W RedZone 4 and a Planet Bike Turbo under worst case scenarios (lowering sun washing out the lights and note the vest works well then, and riding into a lowering sun), here.

Having drivers looking for slower traffic is a very good thing and though it is a longer and slower route, with more traffic, it may be a lot safer. Trust the 'vibes'. Besides a Starbucks trumps a Sewage Treatment Plant in the olfactory department, at least. 

BrianMc


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## m85476585 (Jun 7, 2007)

I made a quick demo/video of the flashing pattern I'm going for. The LED flashes at about 15hz for 7 cycles then stays on for 400ms. The video shows the led directly, with a piece of paper over it, and out of focus with the paper, all in a dark room. The brightness is irrelevant since I'm not driving it at full power, I have no light reference in the video. I have a bunch of these blue LEDs for another project, but I won't use them on my bike since blue is reserved for police. Here's the video:





There is some interference between the camera's framerate (30fps) and the flashing LED, which is why it sometimes appears to flash less. All the timing is very easy to adjust if I want to slow it down.

The LEDs I would most likely use, and the blue LED in this video, are Piranha series by Cree. The red one puts out 7.7 lumens with a 120deg viewing angle at 70mA (about 1/6W). They cost just 0.19 each, so I can easily get lots. 
Digi-Key - CP42B-RKS-CL0P0AA4-ND (Manufacturer - CP42B-RKS-CL0P0AA4)


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## mechBgon (Jan 28, 2007)

m85476585 said:


> ]So I'm wondering if it's possible for my lights to be too distracting?


No, it isn't. I wouldn't advise using a 12Hz assault-strobe pattern designed to disorient, but I haven't seen any bike lights that do, so you're safe there.



> The idea isn't to blind people, just to make myself visible as early as possible and from as far a distance as possible. Does anyone here have experience riding with an excessive number of flashing rear lights? Any tips for riding on this kind of road?


I have tons of experience with that. Start by confirming your existing lights are aimed dead-level and straight back, because the SF Turbo is directional, and it won't do nearly much good if it's not aimed at your targets. Also confirm your SFTurbo is actually on... mine turns itself off at random, frequently.

Consider getting a Cygolite HotShot, which is significantly more powerful, rechargable, and not much more money. I have two and they seem to be reliable. For long-range daytime visibility on a highway (from the direct rear approach), this is a must-have at only $40. Sweat the aim, it's very directional.

Also consider some Bontrager bar-tip lights to give yourself more "width." Bontrager: Trek Beacon Bar End Lights (Model #06988) These are available in flat-bar and drop-bar versions. Use rechargable AAAs because they do gobble up batteries quickly.

In darkness, present as much reflective profile as possible. If you have panniers, get some iron-on reflective tape off eBay and iron on some vertical striping. Also get a neon-lime ANSI reflective vest, Harbor Freight Tools has basic ones starting at $5. Use reflective ankle bands, REI has the good Jog-A-Lite ones for $5. The idea here is to do what you can to be recognized for what you are, at least at close ranges, instead of just a random assortment of weird lights. Although I'd hope motorists associate blinkies with cyclists by now.










I also apply 1cm stripes of high-performance reflective tape to my fenders. The Reflexite v82 from night-gear.com is some of the best for this, very high reflective performance yet thin enough that it doesn't try to peel itself off.



> At the same time I want to avoid attracting too much attention and having drivers fixate on me (causing them to drift closer).


This is a non-issue in real life, don't worry about it. Attract all the attention you can.


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## BrianMc (Jan 5, 2010)

m85476585 said:


> I made a quick demo/video of the flashing pattern I'm going for.


FYI the HotShot has a very similar pattern in its repertoire.

BrianMc


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## WR304 (Jul 9, 2004)

A rear light for a vehicle on the road really should be red. In the UK it's a legal requirement (it probably is in the US too? ). If you use a different colour as your rear light that's going to be confusing and potentially dangerous.

The problem with many LED rear lights is that even though they can be bright the lights and reflectors they're integrated into are often very small, too small really. You only get a small dot of light from the light. It might be bright but that small dot is competing against all the other light sources (cars, street lights, other lighting near the road). When driving a car at night, especially in a city with lots of traffic, a single small LED light on a bicycle is hard to pick out. I know that when I've been driving at night in rush hour traffic the bicycles are often difficult to spot as a result.

The old style 1980s rear lights that used bulbs instead of LEDs had a much larger lens, providing a big block of red light visible from behind. What you want from a rear light is something that's high output with a wide beam spread (something you don't really get with LEDs unless you have lots of them). If you're going to make your own light it needs to be large enough to stand out. The picture below was in Google images and is a homemade rear light where someone bought a tractor LED rear light and mounted it on their bike.:eekster:

_"Even better is LED based tail/brake lights commonly used for tractor/trailors. I have 2 mounted on the rear of my commuter bike wired for full power (brake light mode) flashing ~5 times per second They only draw 0.3 amps but are visible even in very bright daylight conditions. They also have a very wide visible angle, 80 degrees in any direction.

The ones I'm using are Truck-Lite brand LED Super 44 S/T/T and were $15 each on EBay. The flasher is homebrew, wired to a 12V battery."_*cycling forums.com post*

Brightest LED red (rear) light?

Pictured below: This rear light will show up!


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## BrianMc (Jan 5, 2010)

Size matters. I think the brightness champ goes to Leopold Porkstacker's DIY at about 900 lumen total.

There is a max output for vehicle lights, but as I read Indiana law it doesn't apply to bikes.

He also has truck air horns on his Big (Heavy) Dummy.

Here is one source of an LED similar to what he used.

Two can get you 1200 lumens if you want! Brightenuffurya? 

How bright are vehicle lights and an old discussion of what might be too bright here. I have become a bit more of a scofflaw fi it means being alive instead of dead. Short of burning out driver's retinas, in line with mechbgon.

Don't forget the Designshine tailight: 600 lumens.

The

BrianMc


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## BrianMc (Jan 5, 2010)

m85476585 said:


> There's an interesting article here
> Longleaf Bicycles: How the Brain Works and Bicycle Visibility
> on how people are conditioned to look for cars when they are driving, so it might help to appear like a car in some way.


That web page influenced this post.

Many of the same themes as in this thread.

BrianMc


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## WR304 (Jul 9, 2004)

The weather here has been quite miserable for the last few days - lots of fog, drizzle, very grey and overcast. I've had my Cateye TL-LD610 rear light on all the time whilst riding. Visibility in the fog up in the hills was down to as low as 20-30 metres on Monday. The only rear lights of passing cars that showed up at all in the fog were their foglights.

I thought you might be interested in seeing the Cateye LED bike light brightness compared to a set of car rear lights. The pictures were taken at 4.30pm which is dusk roughly. It was just beginning to get dark.

One picture is with the car rear lights on their standard setting and then the other is with the car's rear fog light turned on. The bike light brightness when viewed from a distance is close to the car foglight. The camera loses a lot of the detail but the five individual LEDs of the bike light are clearly visible when you see the actual light. The bike light is actually slightly brighter than the car's rear fog light. The standard car rear lights are much dimmer in comparison. 

Pictured below: Cateye TL-LD610 rear bike light compared with a car's rear lights


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