[GRRiders] Re: Lights being perpendicular

Fri Jul 8 10:41:00 PDT 2005

Eric--
We agree that something is better than nothing; a poorly aligned rear lamp
is obviously better than what you describe from the ER. My experience is not
based upon trauma rooms like you, but from driving a lot of hours in the
dark behind randonneurs during nighttime brevets. As a rider of many years
experience doing brevets I hadn¹t noticed this too much, but in recent years
as a sag driver, there is a difference. Perhaps not huge, but there is a
difference, and given the speed at which a driver overtakes a rider, those
few slim seconds can make a difference to the rider¹s safety and peace of
mind.

But to your points:
You obviously haven¹t looked at the route profile of the GRR or paid
attention to the ride reports on-line. The first and last 100 miles of the
route are pancake flat. On the outbound, darkness will fall for most folks
after about 40-50 miles or so, leaving a good 50-60 miles in the dark. Then,
after Jarbo Gap is climbed, the long ride up the Feather River Canyon is a
very steady grade that appears flat, so more of the same thing. In 2001,
during the last night getting back to Davis, most riders were on this
100-mile section after leaving Susanville around darkness, so they rode a
century in the dark on flat ground with only a couple levees to climb.  At
any rate, in hilly areas, with cars having less time to see the riders due
to the ups and downs, or especially due to the curves, I believe alignment
is equally important there too. I know it has been to me as a sag driver, no
matter what type of terrain the brevet goes over.

The beam pattern of tail lamps is pretty much as you write, but I think
you¹re missing the point of the overtaking car driver some hundred yards
back or more, not standing nearby it or riding close behind it at the same
speed. A car going 60 mph is another matter. The sooner the driver sees that
something is up ahead, the sooner s/he can start to adjust their driving
speed and placement in the lane. It is a speed/reaction time ³thing². What I
have noticed about this while sagging brevets is that some riders seemed
more visible than other. At first I thought this might be from low
batteries, but upon looking carefully at the riders as I drove by, I have
noticed the ones harder to spot often had their lights somewhat off the
perpendicular (usually because the lamp was mounted on a seat stay and
probably couldn¹t be angled downward enough. Or, others had their lamps on
Camelbaks, which in the standing position would be fine but when the rider
is crouched over the handlebars they were less effective.) Lee Mitchell,
route monitor extraordinaire, says the same thing. Given our collective time
riding behind randonneurs and other nocturnal cyclists, I don¹t believe this
is mere anecdotal evidence, but with the sheer number of opportunities we
had to observe this phenomenon, that counts for something.

True enough that being close to a rider with LEDs, especially blinking ones,
can be annoying. I agree.* However, our main concern is problems with
overtaking motorists, not other cyclists. I think what happens to many
riders is that they install their rear lamp and think the job is done so
long as it is ~pretty close~ to perpendicular. Consider, though, that if the
bike is on the floor, the lamp is about 2-3 feet above the ground or so. The
person standing nearby doing the installing is crouched down next to the
bike, looking at it, and it seems fine. Then they stand up and look at it
again, and it seems similarly good. And, out on the road, other riders don¹t
notice the alignment too much due to their proximity to the other cyclists.
I was in this group when I was doing more riding in years past. However, in
recent years, as I am doing more sagging these days, now I notice a
difference. I would suggest one walk backwards from their bikes in a very
dark environment (like a really dark country road) at least one hundred
yards or more, as if they were a motorist overtaking the rider with ³low
beams² on, and the rider is not yet in the car headlights. I have done this
experiment with two identical lamps (one on either seat stay) and do see a
difference.  Yes, an upward angled lamp one can be seen, but the one
perpendicular to the road is brighter to the overtaking driver.

*(About annoying other cyclists on your wheel, I run a Œwimpy¹ LED on steady
all the time mounted on a seat stay, but also use a good Vistalite (sp?)
too. This is attached to my seat post. When in a group, I reach behind and
turn it off on the fly. When alone, or at the tail end of a group, then I
switch it on.)

At any rate, you seem to be speaking from your ER experience with
idiots/drunkards who don¹t use any sort of night gear; come volunteer to
drive sag on some all-night brevets and I¹ll show you what I¹ve learned.

Bill Bryant

> 
> 
> 
> 
> 
> 
> 
>  This perpedicularity of lights seems like just so much BS to me.
>  
> 1. As an anesthesiologist at a trauma hospital every cyclist I have taken care
> of who was hit riding at night had no head or tail lights, was wearing dark
> clothing and had no reflective material. Randonneurs present the antithesis of
> this model when riding at night.
>  
> 2. The roads we ride are not flat. Therefore a cyclist with perpendicular tail
> lights, beginning to ascend a hill will have lights pointed well below the
> direct line of vision of a driver descending the hill just behind the cyclist.
> There are almost limitless variations between the direct beam of the tail
> light and the approaching observer. Regardless of the angle (within reason) I
> have no trouble seeing cyclists ahead of me in the dark 1/2 to 1 mile ahead
> (depending on the terrain)  unless I am blinded by the headlights of an on
> coming vehicle. 
>  
> 3. Tail light lenses broadcast a wider beam of light than the headlights that
> we use. The headlight beams are focused for the rider to see where he/she is
> going and the taillights cast a broad beam for the rider to be seen. Some
> thought was give to visibility by the engineers who designed the taillights.
> Even at 145-160 degrees from the center of the beam most tail  lights are
> still very visible so, a few degrees off the perpendicular has little or no
> effect on ones overall visibility, especially if one has two or more tail
> lights.  
>  
> 4. Bill, If you want to give a logical reason for having the lights
> perpendicular it should be so that the brightest beam of the tail light is not
> focused directly in the eyes of the cyclist behind you, just as the blinking
> mode becomes distracting and irritating the bright center is irritating and
> causes the night vision of the following cyclist to be reduced.
>  
> I would especially like to here from our engineering trained randonneurs on
> the subject as my diatribe is based on personal experience, observation and a
> limited knowledge of physics.
>  
> Eric Simmons
>  
>  
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