closetbiker

Does anyone know of any good studies that have been done showing whether or not judging distances from a steady, oncoming light is any more reliable than a flashing, oncoming light?

I know this is much discussed, but don't know if all that been shown is anything more than speculation.

I remember when the flashing rear lights came out, there was discussion on whether or not one could judge how far up the road the lights were, but it was agreed that the flashing lights were much more visable than the old steady rear facing reds.

I couldn't wait for the white LEDs for the front, but now that they're here, I'm reading that distance judging problem could result in inadvertant cut offs because the drivers cutting off the cyclists couldn't tell they were as close as they were.

cyccommute 

There's this one but it kind of old. I haven't read it.

Here's one on snowplows.

Here's an interesting article on optical illusions that explains some of the problems.

cyccommute 

I found another one: Croft, T. A. 1971. Failure of visual estimation of motion under strobe. Nature 231:397

My library has it but I have to go look it up.

closetbiker

Thanks.

BarracksSi

In that first link:

"Nearer lights tend to be judged as being farther away then they actually are,..."

That's a dangerous misjudgment. I know that I have trouble judging distance myself when presented with a bright flashing light.

It depends on the time of day whether I choose flashing or steady. During the daytime, I choose rapid flashing. It's more attention-grabbing, and a rapid flash is more likely to be spotted as a driver makes a split-second glance to the side.

I run a steady light at night for better distance estimation. In the dark, until another driver/cyclist/jogger/dogwalker gets close enough, my light is the only thing they can see; they don't have the advantage of seeing my body & bike like they do in daylight. I've also used two headlights for even easier distance estimation if I'm around pedestrians -- although I now think it's smarter to avoid pedestrian-heavy areas in the first place.

Two of the three flash patterns on Dinotte lights are partially steady -- that is, the flashes are supplemented by a constant low-power light. I think it's a good blend that works for most conditions.

closetbiker

for all my worry about whether or not someone might cut me off at night because of poor distance perception of a flashing light, the only times I've been hit in a cut off, it was light in the daytime (and I spend half my time riding in the dark)!

Giro

I have been reading on bicycling safety in general. One distinction made in the literature is the detection distance ("something is there") versus the recognition distance ("its a bicycle reflector, not a beer can"). This can be an important distinction regarding bicycling safety.

I found a few publications of interest regarding flashing lights, although they do not discuss the tracking issue per se. Somewhat to my surprise, studies are mixed if flashing is or is not 'better'. This may be because this is a complex problem with many variables (urban, suburban, or rural; ambient lighting; light's intensity; background of other lights, etc.) that may not have a simple, consistent answer.

There is a collection of reports at Loughborough University Institutional Repository in the UK at LINK. The most relevant ones on lights are LINK1 LINK2.

I also found two reviews on cyclist and pedestrian visibility:

"Visibility aids for pedestrians and cyclists: a systematic review of randomised controlled trials" ABSTRACT

"Interventions for increasing pedestrian and cyclist visibility for the prevention of death and injuries" ABSTRACT, which cites:

Watts 1984c
A flashing beacon on a bicycle yielded a greater detection but not recognition distance when compared with reflectors (588m versus 444m and 59m versus 71m respectively).

Markowitz 1971
Markowitz J. Optimal flash rate and duty cycle for flashing visual indicators. Human Factors 1971:427–33.

If anyone wants more details on the two reviews above, please private messenger me.
_________________________________________________
“Complex problems have simple, easy to understand, wrong answers.” - H.L. Mencken

closetbiker

Thanks (again) I'll try to read it today.

as a side note about only being hit in the (light of) day, every time I had a chance to ask the person who hit me if they had seen me before they cut me off and hit me, they all said * yes *

Cyclist0383

^^^

The question is how much before and if either a strobe or steady light would have made a difference.


FWIW I use a strobe is it is much more attention getting in urban traffic.

cyccommute 

Thanks for the posts. I haven't read through them completely yet but I found a couple of things that are interesting in your LINK1

In section 5.3.6, they state "warning beacons ...contain an element of distraction...significantly in the driving environment, their use should be kept to a minimum." This is in reference emergency vehicles but it does seem to say that getting peoples attention is one thing, overwhelming them is another. Current police vehicles seem to have gone to the overwhelming side of the equation.

And in section 3.1.3, they state "for small motorycycles, a 50% increase in headlight power increased conspicuity distance by 350%..." This is something I've been advising people to do for years. Lots of people think that you don't need that much light in an urban environment. I think you need more to keep from getting drowned out by all the other interferences.

ccd rider

I would say detection would lead to recognition. If you notice something near the road from a great distance you will probably keep paying attention to that until you recognize it. If something is bright enough to gain that attention from as great a distance as possible, it gives the motorist more time to react to the situation.....even if they don't initially recognize it to be precisely a flashing light from a bicycle.

As far as depth perception of flashing lights.....what kind of studies have been done SPECIFICALLY on that? My view is to be noticed, period. If someone doesn't notice a steady light it won't matter what their depth perception is. My thinking is that if someone sees you and can discern after that you are a bike rider....then they will adjust to going far enough around you, behind you, and ultimately back in front of you by going BEYOND what it is "just far enough" to get around you. I will trade any sense of someone in a vehicle possibly misjudging where you are on the road when maneuvering around you for INITIAL DETECTION any day of the week. They have to know you are there before they can do any maneuvering! And I'm not convinced that a steady light is going to garner the same attention as something that flashes. Flashing is annoying.....that's why people notice it!

Along those lines....yes....there probably is a practical saturation point for what is "overwhelming". But who gets to decide that when it's my life that could be in the balance? I would say as long as it's not so bright as to literally blind an oncoming motorist....then it should be okay. If it's too "distracting" that's your problem as a motorist. I want you at least temporarily distracted, yes. There's no reason a driver has to be "fixated" on the bright lights on my bicycle. Someone else argued about how bright a car headlight has become these days....but when is the last time you saw a motorist getting a ticket for blinding the crap out of a bicycle rider? So....push it to the edge. Check your local laws and abide.....but I would say push those right to the limit. If I have to break a law to keep myself alive, I might just do that. Laws are made to protect all people.....and they are subjective in at least their initial make up (and often even afterwards in their interpretation). And laws are typically made by people who think they know what is best for all.....but perhaps don't have all the insights necessary to make a completely responsible determination. Why do you think there are so many variables from municipality to state to federal views on things? Not saying they are all arbitrary.....just arguable.

We can argue all day about what is best, but MOST of that should be up to the discretion of person who legally puts themself in that situation. Within reason, someone's individual liberties should be paramount.

ccd rider

Just as an addendum to my initial rant, I would also wonder how many of the good folks who make laws......or do these studies have ever ridden a bike at night on a highway? I would rather have a consensus of anecdotal evidence from actual riders (or from my own experiences!) than from a science experiment, thanks.

Also, I read the report on the snowplows. It talked about the motorist being able to discern the deceleration of a snowplow from behind better with steady lights. Why is that even an issue? Why are you so close to a snowplow truck that you would even need to make that kind of a judgement??? Not only are they kicking out sand/salt out the back which could damage your vehicle.....but there are a whole host of potential items in the road that they could kick up with their plows. I drive a snowplow in the winter for the college where I work, and it's amazing to me how much people don't take those things into consideration. It makes you wonder whether making any rationale decision on such matters would make any difference......flashing or not.

And let's say we put some figures out there for safe distances and/or the proper clearances for going around a bike rider with flashing lights. You see the snowplows already that have signs on the back warning of staying back so many feet for your safety. But how many people even pay attention to them? OR would even know how far 50 or 100 feet is??? How many drivers do you know follow the car length per 10 mph rule? Ha, ha!

I'm not trying to be cynical....just realistic about human nature. There is no utopia. Even if 99% of drivers out there were adhering to all of the rules (which is comical)....I would still worry about that 1% of knuckleheads who don't.

CdCf

I can't stand looking at a strobe myself. I look away. I'm certain many drivers do the same. How does THAT help your safety?

Steady all the way, all the time, for me.

acroy

I think that the main point to keep in mind is that we, as cyclist, want not just to be seen, but to be recognized and not hit!!

to this end, anything we can do to help drivers not just see us, but to recognize us for
a) what we are
b) where we are
c) how fast we're going

is going to help increase our chances of survival

To this end, stuff like wheel, pedal, and ankle reflectors help a LOT. a blinkie or 2 with no other frame of reference is no help at all. An uber-bright front light just blinds them, they don't know what you are or how fast you're going. Drivers have to just guess.

I'm lucky in that a lot of my coworkers drive by me on the way to work. I ask them what helps the most. My bright blinkie & headlight let me be seen. Concensus is that the reflectors help them a lot to recognize and "place" me on the road, and thus drive around me without guesswork as to where and how fast I am.

Cheers & be safe

BarracksSi

Depth perception, as expressed by "distance estimation", has been studied. The results say that the distance of steady lights is easier to judge accurately.

And, no, I'm not going to trade better initial detection for poorer distance estimation. If someone sees me at a glance and doesn't realize that I'm only 15 feet away instead of 30, then that's going to be a problem.

That's why I do what I do: run a bright, flashing light for quicker detection, and also run a steady light -- but still bright -- for better distance estimation.

PS - "car length per 10 mph" is overly complicated and still doesn't address the logarithmic nature of increasing speeds & distances required for braking. The 2-second rule (or three seconds, etc) is much easier to follow.

closetbiker

I too, talk to a lot of my co-workers about what they can or cannot see when I'm either coming in or leaving work.

I find their input invaluble.

Giro

Good & enlighting thread. I think we agree that different methods may be better in different situations. Some of the published research might help you choose which methods may be best for which situations.

Regarding detection versus recognition as a bike, research cited in "Visibility aids for pedestrians and cyclists: a systematic review of randomised controlled trials" found some visibility aids had better detection distances but worse recognition distances.

For example, a study of flashing beacon vs. reflectors:Thus in this study a flashing light was detected farther away but it was recognized as a bicycle at a shorter distance than reflectors. I want to read the study's details, but I may add more reflectors for earlier recognition as a bicycle despite using a DiNotte tail light on steady+flash.

The other cited studies make me want to use reflective tires and biomotion to increase early recognition (e.g. could a DiNotte tail light be attached to the left leg?).

As I offered before, if you want details on these studies, please private message me.

GlowBoy

Flashing and steady for me. IMO early detection is invaluable for reducing the incidence of conflicts -- the more time motorists have to identify and figure out how to deal with me, the less likely there will be a problem. Having some blinking component to my profile helps me stand out from all the other visual noise so that motorists (who, around here, ARE used to dealing with cyclists) know there's a cyclist in the mix.

But there's no substitute for steady lumens, especially in front. Essential to helping people quickly judge your location and speed. I have steady LED running lights on both ends of my bike in addition to my 1200 lumen headlight.

znomit

What do the ones who don't see you at all say? They are the ones who are going to run you over tomorrow.

BarracksSi

How many lights have a blinking pattern that blinks while sustaining a dimmer setting? That is, it's always lit, but it gives pulses of bright light at the same time?

The two Dinotte lights I have (200L headlight and 140 taillight) both have two flash patterns like this; any others?

closetbiker

welll, they're the ones that are a problem aren't they? Or, are the ones who see you and still hit you the bigger problem? Usually these are the ones who get into car wrecks every couple of years (and say I'm the one who's taking "chances" on the road)

At any rate, most offer unsolicited opinions during the day. Occasionally, someone'll say they passed me and I might ask how I looked, visability wise. What they noticed, or how it was they knew that it was me.

More people have commented on the flashing lights than the steady lights. A couple of times, when I've had a strong steady light and a flashing light on the helmet, they've mentioned they noticed the flashing light and when I asked if they noticed the steady light, they've said, no, just the flashing one.

Giro

The Cateye L1000 'pickle' rear light has two banks of lights, each with a switch that cycles through various options. You should be able to set one row on steady and the other on one of various blink modes. Their newer and brighter L1100 is reportedly less complex, so it may or may not have that option.

BarracksSi

Oh yeah, I've got that one... heh, the "pickle"...

The thing about it, though, is that even when one is set to steady and the other to blink (and not the back-&-forth pattern, just on-off-on-off), it doesn't really appear brighter when it blinks on, if you catch my drift. There are more lights, but that's different from having brighter lights. Move far enough back, and it only looks like one light flickering somewhat.

Not my vid, but one of the best-filmed comparisons I've seen anywhere that includes the LD1000:

https://youtube.com/watch?v=fl5y72POyiU

T Waldo

I agree fully about biomotion. That's one thing that often gets left out of the detection/recognition debate. The agents driving cars are HUMANS, and anything that immediately lets them know another HUMAN is on the road (vs., say, a random reflective sign) is to our advantage. I'm still amazed when I'm driving by how quickly my brain registers legs in motion by the time-tested pedal reflectors going up and down on a cheap bike.