Sunday, August 31, 2014

Bicycling's "Light Up the Night" Suggestion for a Headlight



Or, Why This Is A Bad Approximation At Best


I was reading through the latest Bicycling issue (October, 2014). On page 26 is a one pager on lights and reflective stuff. Interestingly, the article states that a 100 lumen headlight should work "for most situations". But then down in the lower right hand corner of the page is a little picture that is titled "the right light" and which suggests that a 100 lumen light is good to a range of ten feet while a 500 lumen light illuminates to 50 feet and 1000 plus lumens to 75-100 feet.

Ten feet?? A commuter cyclist riding at 10 mph covers ten feet in about two thirds of a second. Assuming Bicycling has its numbers right on light range, 2/3 of a second is barely time to think "oh, shit" as you note the pothole or piece of lumber you are about to hit.

There is a lot more to lighting then lumens and more to this story than lumens. For one, the shape of the beam determines how the light is distributed, which affects lux, which is actually more important. Lux is a measure of how brightly something is illuminated, i.e., lumens per square meter, so a light that puts all of its lumens in a narrow beam will illuminate brightly for a longer distance but leave anything west or east of dead ahead in blackness. The link from the Appalachian Mountain Club used the example of a full moon illuminating the earth to about 0.25 lux. Likewise, not all of us have equally good night vision and some of us need more lux than others. Luck, too. So let the buyer do some serious R and D before purchase.

But just taking that little graphic in the corner of pg 26 at face value, what can one say about how much light you need to get out to a distance of say, 1 to 3 seconds. 1 to 3 seconds is the broad measure of human reaction time in traffic. So what really matters to avoid that pothole is to be able to see it in time to do something besides hit it. I put Bicycling's range vs. lumens into a graph and used that relationship to solve for a 1 to 3 second range at various speeds. This is what I got.


Bicycling's 3 points put on a graph

At a given speed (abscissa), the number of lumens (ordinate) will, in Bicycling's model, illuminate the road 1 to 3 seconds ahead
As Stuart mentions, this is a little strange given that if you assume the light is illuminating to a given distance and that the beam widens with an angle, say, theta, the area illuminated increases with the square of distance. Hence, you should need lumens to go up as the square of distance at constant lux. Is that correct? My hunch is that Bicycling's numbers are not rigorously scientific, but rough estimates as to what works. But I'd be surprised if it should be linear.






Mind you, this is more of a thought exercise and not hard and fast advice, but if you are thinking of buying a light (and Fall is coming up fast), you need to think about how fast you are going, the roads you are on, and therefore, how far out you need to see. You also need to think about whether you need a light that distributes light side to side (to avoid those raccoons darting out from the side of the road, etc).  That is a highly individualized decision and goes far beyond "...should work for most situations".

Other stuff on this blog having something to do with lights.


Saturday, August 30, 2014

"Science flies you to the moon. Religion flies you into buildings"


My old friend and Univ of Hawaii colleague Vic Stenger (Physics Dept), owner of the quote in the title of this post, passed on this Wednesday. Vic had no use for religion, so I will spare this blog a homily. So long, Vic.

A brief synopsis of Vic's life is here at the Huffington Post, where he was a regular contributor.Here is a neat essay Vic wrote in Huffington, "Science is Politics".


Wednesday, August 27, 2014

NPR: Next Time You Want My Money, Forget It


Share the Road. Share the Love
Recently, NPR ran a story on cyclists cycling in groups in Los Angeles, and that story included a quote on how a motorist in LA bragged about buzzing and potentially hitting a cyclist. Apparently that got enough bad press that the NPR Ombudsman responded with another article. Well, no good deed goes unpunished, and among the worst comments that second post received were some by a person posting as a Jim Johnson, who had such gems as

"Bicyclists don't belong on streets or sidewalks. You are freeloaders and pests."
"I am okay with "vigilante justice" applied to bicyclists."
"Bicyclists need to know just how despised they are."
"Bicyclists are self-entitled freeloaders"
"Oh, I wouldn't be so blatant as to drive into a cyclist. But how would you like to be followed for the entire duration of your ride by someone who's leaning on the horn? There are plenty of ways to spoil your fun without actually touching you."
"But I am here. And behind the wheel. And you had better keep that in mind, because I'm not the only irritated driver."
"Better be careful when you're alone is all I can say."
"The difference between you and me is that I really do carry a gun in my motor vehicle. Spandex boy, this is not a fight you want to start."

Mr. Jim did his best troll imitation, trying to hijack the entire discussion thread with threats and abuse. I tried to report some, but as most of us know, Disqus is relatively insensitive to reporting abuse. Likewise, I tried to find a way, any way, to contact NPR's Ombuds. I left a phone message which was not returned and one of those "fill in this little box and some day, in your next life, if you are really lucky, we will get back to you" comment pages.

I find it interesting that it is soooo easy to reach NPR when they want my donation, and almost impossible to reach an executive, board member, or ombudsman when you want to say something of substance. So NPR, do me a favor. Don't ask for my money any more, either. I'll try to be as hard to contact as you are.

Wednesday, August 20, 2014

Don't Forget to Ride the TORGV



Hello bicyclists,

Hope you all will ride the 2014 TORGV with your friends, FAR FLAT FAST FABULOUS AND FUN!

Registration info at www.TORGV.com both mail-in and electronic.

Proceeds go to supporting the Bicycle Coalition of NM’s (a 501 c 3) advocacy work to support safe and fun bicycling in NM.  BCNM is the only state-wide advocacy organization that works at the national and state level for bicyclists’ rights.

Optional jersey for sale this year!

Tandem riders ride for a $60 fee, not $120!  Spread the word to your friends!mi

DIANE

Diane E. Albert, PhD, JD
Vice President and Board Member, Bicycle Coalition of New Mexico (BCNM)
League of American Bicyclists LCI #2292

Greater Albuquerque Bicyclists Advisory Committee member

League of American Bicyclists National Board Member

P.O. Box 30548
Albuquerque, NM 87190-0548
505.235.2277
www.BikeNM.org

Tuesday, August 19, 2014

Lessons From The Last Time Civilization Collapsed

Go over to National Public Radio and read this.

"Consider this, if you would: a network of far-flung, powerful, high-tech civilizations closely tied by trade and diplomatic embassies; an accelerating threat of climate change and its pressure on food production; a rising wave of displaced populations ready to sweep across and overwhelm developed nations.
Sound familiar?
While that laundry list of impending doom could be aimed at our era, it's actually a description of the world 3,000 years ago. It is humanity's first "global" dark age as described by archaeologist and George Washington University professor in his recent book ...."

Wednesday, August 13, 2014

School Starts Tomorrow....be careful out there



With school opening tomorrow, we can expect the usual mass confusion and heavier traffic than we have seen in the last few months.  Watch out for distracted or harried parents ferrying their kids to our various schools (while blocking bike lanes and pulling across your path).

In addition, I would suggest that that folks bicycling or motorcycling to LANL along the Diamond Drive corridor should be extra careful in the section of Diamond Drive between North Road and the Omega Bridge. There are numerous side streets and curbcuts (driveways) where students will add to the existing confusion and we can expect a lot of sometimes oblivious turning and crossing traffic. Several of my LANL colleagues have been decked, at least one suffered major injuries, and many of us have had near misses, myself included.

Be careful out there and if it’s your teen driving to the H.S. make sure he or she takes those car keys seriously.  Like loaded guns and alcohol, smart phones and moving cars don't mix very well.