Category Archives: lighting

Daytime running, nighttime blinding

Here’s a sign I just noticed for the first time, on the Minuteman bikeway, outside Boston.

Sign on Minuteman Commuter Bikeway

Until LED lights went on steroids, who would have ever thought that this would be a problem? But then, unregulated industry is ever willing to find an answer to a perceived need.

Do you think that major bicycle manufacturers are straight about safety, any more than, say, auto manufacturers were until their feet were held to the fire by Ralph Nader’s book Unsafe at any Speed and the Federal regulations it led to? (Not that auto manufacturers are straight about safety even now, witness the commercials of cars being driven at insane speeds, but that’s another story).

Latest example: Trek’s campaign for daytime running lights — not a bad idea, but I have some real problems with Trek’s advice.

A light that is visible from a long distance in daylight is blindingly bright at night. Light-emitting diodes have become so efficient that this is entirely possible with a small, battery-powered headlight. Trek markets and sells lights designed for daytime running and improperly designed for nighttime use. Trek claims that these lights are visible at distances up to a mile in daylight. These lights shine into people’s eyes and blind them at night (as with many other brands as well).

This trend is abetted by the “more is better” syndrome. Brighter must always be better, right? There are even lights marketed under the name “blinder” and “supernova”. I kid you not. Look them up on the Web — you’ll find them.

The round beam pattern of Trek’s headlights is inappropriate for nighttime use. A headlight used at night should have a flat-topped beam pattern. Automobile headlights have one. German standards for bicycle headlights require a flat-topped pattern  (not surprisingly, as a lot of bicycling in Germany is on paths, and German regulators are sticklers about detail). You may read about very fine headlamps from Germany on Peter White’s web site. In the Boston, Massachusetts area, Harris Cyclery sells them, as do other discerning bike shops. (Disclaimer: a write for a Web site which has a business relationship with Harris Cyclery). Lights with a flat-topped beam pattern are available from some Asian manufacturers, too.

Trek’s advice doesn’t avoid mentioning blinding people, and also doesn’t mention the pedal reflectors or ankle bands which are required by law in Massachusetts, or the rear reflector which still alerts overtaking drivers if a taillight quits or becomes dislodged. Trek taillights do not include an integral rear reflector. Laws vary from place to place, but they generally require a steady taillight or rear reflector at night. A blinking taillight alone is hard to track with the eyes.

To use a headlight properly designed for nighttime use as a daytime running light, just tilt it upward a little so it shines into people’s eyes!

Above all though, safety needs to be active, not only passive. “Being visible is key to your safety on the road,” says Trek. Well, yeah, but lights protect you only when there is a clear line of sight between you and the person who needs to see you. Ride to be visible, and that means, among other things, pass on the left, not on the right, and on a narrow, winding country road, merge away from the right edge as you enter a blind right-hand curve.

A more detailed discussion of bicycle headlights is at

A more thorough understanding of how to be safe can be gained by taking a CyclingSavvy course, or a League of American bicyclists Smart Cycling course, Can Bike course (Canada), ROSPA Cycling Proficiency course (U.K.) reading the booklet Bicycling Street Smarts, John Franklin’s book Cyclecraft, John Forester’s Effective Cycling… Disclaimer: I am a CyclingSavvy and League of American Bicyclists instructor, and I wrote Bicycling Street Smarts.

But why do I do these things? Because I want you to be safe, to give a quick answer.






About the bicycle radar reflector Kickstarter campaign

This article has been translated into Portuguese. Brazilian flag
This is commentary about a Kickstarter campaign for a radar retroreflector integrated into a bicycle taillight assembly.

An image from the Web site:

Image from Ilumaware Web site

Image from Ilumaware Web site



One nice thing I can say about the product is that it is quite inexpensive, so I’ll say that first. The reason is that this is not a high-tech product. This is a low-tech component of a system whose high-tech component is in cars.

Retroreflectors work by concentrating light (or in the case of a radar reflector, radar signals) back toward the source. The product is a single cube-corner retroreflector. Optical retroreflectors are the insect’s eye version, with multiple smaller reflective elements, so they work at the much shorter wavelengths of visible light. The technology is described on another Web page.

As to the effectiveness of this product, I have no doubt that it improves the visibility of a bicycle to radar — but…

The product’s Web site repeatedly uses the term “OTR technology”, without ever spelling out the meaning of the acronym. I couldn’t find a definition anywhere online, either. This term makes the product appear more high-tech than it is. Indeed, the site claims:

Stealth techniques use radar reflection to make an object less visible and/or “invisible” to radar. We have reverse engineered this technique into a product used by a cyclist to make you more visible to a car. This is a revolutionary application of radar technology.

Reverse engineering is correctly defined as analysis of an undocumented product to develop specifications for a duplicate or similar product. Examples are the Wright brothers’ reverse engineering the flight characteristics of birds to design aircraft, and Linus Torvald’s reverse engineering the proprietary Unix computer operating system to construct the Linux operating system. The Kickstarter campaign uses the words “reverse engineered” inaccurately, so as to mislead people who do not understand it, as if to mean design of a product to have the opposite effect of an existing product. And when that product is a stealth bomber — wow, now the new product must be extremely high-tech! Again, the product is a simple cube-corner radar retroreflector, as has been used in boating for decades. The designers describe design and optimization of their product, but this is plain vanilla engineering, not reverse engineering.

A radar retroreflector which works in all directions is more desirable, (though it still will not always work, even if a car has radar, because the radar beam may not be aimed in its direction, and there may be a line-of-sight obstruction).

Radar alone as a robotic aid to a human driver is possible, but not very practical. Only a small percentage of cars have radar as of yet. A human driver uses visual cues. A fully-robotic car also must, because not every potential obstacle will be as large or reflect radar signals as well as a bicycle — think potholes, cats and dogs, etc.

The product, as shown on the Web site, includes an active taillight, but no optical retroreflector — though installed in the same location on the seatpost which is usual for one — following in the long tradition of new products promoted as a panacea for cyclists’ conspicuity problems while ignoring basic legal and functional requirements. Most states require a retroreflector or taillight, but any taillight can go out without the bicyclist’s being aware of that, and so any bicyclist who rides after dark should have a rear-facing retroreflector, not only a taillight.

The online promotion entirely fails to mention the need for a headlight, or the legal requirement for one. The Web site shows a bicycle with no headlight.

A bicyclist must always use a headlight at night, because an optical forward-facing reflector does not alert pedestrians or drivers who do not have headlights aimed at the bicycle (cars backing out of driveways, at stop signs in side streets, other bicyclists without headlights, etc.) Still, unlike the optical retroreflectors on bicycles, a forward-facing radar retroreflector is likely to be effective, because a car’s radar is likely to scan in more directions and its pulsed output is immune to interference from other sources. But the retroreflector here is only rearward-facing.

The online promotion also makes a number of inaccurate statements.

 Riding with a tail light [sic] is important regardless of the time of day.

While a very bright taillight can help to alert drivers — human or robotic —  during daytime, reducing the probability of a collision somewhat, there is no law requiring a taillight (or rear-facing optical retroreflector) when riding during daytime.

* “In 2015, more than 35,000+ collisions occurred between cars and cyclists in the U.S. Approximately every 3 minutes, world-wide, 6 people die and nearly 285 people are injured in collisions involving cars and bicycles. The majority of these accidents are from behind because drivers didn’t see the rider and it is NOT because they did not have a tail light.”

This is wildly inaccurate. While rural car-overtaking-bike collisions are disproportionately serious and fatal, only approximately 7% of car-bicycle collisions in the USA are car-overtaking-bike collisions. A very large percentage of these occurs to cyclists riding at night without a taillight! In urban areas, most of the serious and fatal collisions involve turning and crossing movements. No rear-facing conspicuity equipment —  optical or radar retroreflector, or taillight, will prevent most of these. Sure, many if not most car-overtaking bike crashes could be avoided, day and night, by use of a radar reflector, if cars have radar connected to a robotic crash avoidance system — but again, as of yet, only a very small percentage of cars is so equipped. Which takes me to my next quote:

* “In 2016 … there are 470 out of 566 unique car models sold in the U.S. equipped with radar (83%).”

This is very seriously overstated. Saying that a model is equipped with radar is not the same as saying that radar is standard. Adaptive cruise control is still often an expensive option. Only some adaptive cruise control systems include automatic crash avoidance. Some systems use laser ranging rather than radar. The fleet of motor vehicles turns over slowly. More even-handed estimates are found in this article in the Detroit News. Quote from that article:

IHS Automotive forecasts 7.2 percent of vehicles produced globally by 2020 will feature adaptive cruise control, up from 2.2 percent in 2014.

More details and a list of vehicles are on Wikipedia.

Why do promotions like this occur? Fundamentally, because regulation of bicycle equipment in the USA at the Federal level, where equipment standards are set, is a Wild West situation, harkening to the interests of the bicycle industry. That is another story, too big to cover here.










About bicycle lighting and onions

A chance meeting can lead to unexpected discoveries.

I met and spoke with Kurt Cibulski following a reading from a new book by its author, a mutual friend. I had arrived at the reading by bicycle; Kurt and I were talking bicycling. Kurt explained that he has a seizure disorder. The bright, rapidly-flashing LED headlights that bicyclists are increasingly using can initiate a seizure for him. “Who’d ‘a’ thunk it.” thought I.

Who? A proper, national standards-setting body, because someone, somewhere, would have brought the issue to its attention. On second thought, it’s obvious. Flashing lights are well-known to trigger seizures.

It’s also a truism that flashing lights draw attention. Many bicyclists ride in urban areas with overhead lighting, and don’t need a steady headlight beam to guide their way. But on the other hand…there’s the seizure problem.

Without careful standards setting, issues like this slip through the cracks. Designs get based on whim, commercial appeal, economies of production and avoidance of liability risk.

In the USA, individual cyclists are held responsible under state laws for using lights at night, but law enforcement is near-nonexistent, and many cyclists don’t use lights. The USA does have a Consumer Product Safety Commission, which, under pressure from the bicycle industry, has set standards — weak standards — only for retroreflectors on bicycles, never for lights. Retroreflectors only work for drivers whose headlights are pointed at them, and do not light up for the pedestrian stepping off the curb, the motorist in the cross street ahead, two bicyclists on a path approaching each other head-on. Bicycle manufacturers can point to Federal regulations and say that they are doing something for nighttime safety, while not being held responsible for these deficiencies.

This situation holds some ironies and unintended consequences beyond the obvious one that cyclists are being injured and killed for want of lights. The lack of standardization in the USA has given lighting manufacturers free rein to innovate, and has led to the availability of some very fine bicycle lighting systems. In the USA, when you see a cyclist with a light, you will probably see that cyclist from a good, long distance, because the light is a very good light.

In Germany, by way of contrast, lights are required on new bicycles. Manufacturer pressure comes to bear in a different way. To keep expense down, most lights only meet the letter of the law and are are less bright, and much less reliable, than the good ones sold in the USA. Bureaucratic inertia has compounded the problem: Germany requires bicycle lights to be powered by a generator. That made sense 40 years ago when battery lights were weak and battery replacement was expensive. Today’s efficient light-emitting diodes and high-capacity rechargeable batteries make battery lights economical and practical.

Generator lights also have improved, thanks to advances in technology and to discerning European cyclists’ demand for better lights that also meet the requirements of their laws — but a good generator lighting system can cost half as much as the bicycle on which it is installed.

A restrictive legal climate leads to this kind of market distortion; contrast this with the wider scope of innovation and slip-through-the-cracks issues in the US market.

I can’t help noticing that kiosk “bike share” (actually rental) bicycles that are becoming popular in American cities all are equipped with LED headlights and taillights, powered by a generator in the front hub. It only makes sense. The rental agencies have a more direct liability exposure than bicycle manufacturers who sell to individuals. But — the lights on the rental bicycles flash, because the generators produce alternating current and the output is not smoothed. Possibly also because flashing lights are popular and nobody though of the seizure-disorder issue.

Where are we heading with all this? I think that we’re approaching a political tipping point where regulations requiring lights on at least some kinds of new bicycles might be possible in the USA: both because of an increase in interest in utility cycling, and because improving technology had made bicycle lights much less expensive, more reliable and more compact. I mean, if little children can have flashing LEDs in the soles of their shoes, just to look cool, it isn’t much of a leap to think that every new utility bicycle could be equipped with lights.

But we also need to be smart, and look forward as technology improves, so regulations don’t box us in with outdated technology and inferior products, as in Germany.

Now, about those onions:

To give Kurt proper credit in this article, I asked his name and came up with another unexpected discovery. He spelled his name, and then volunteered, “Cibulski means ‘onion man’ in Polish. It’s a pan-European word.” Yes! Again, who’d ‘a’ thunk it? German, Zwiebel. Spanish, cibolla. I looked it up, and found variants in languages as diverse as Basque, Czech, Gaelic, Norwegian, Romanian…

I suppose that there’s another parallel, besides the two unexpected discoveries. Bicycle lighting issues, with all the political and technological complications, peel apart in layers like an onion, too.

Thanks, Kurt!

Tipping point for electric bikes?

I have just returned home from the 2010 Interbike bicycle trade fair in Las Vegas.

This was the year for electrically-assisted bicycles – over 40 booths displayed them. Here are some examples:

Lahaina electric bike, essentially a conventional bicycle with a motor in the front wheel and a battery on the rear rack.

Nirve Lahaina electric bike, essentially a conventional bicycle with a motor in the front hub and a battery on the rear rack.

The Nirve Lahaina electric bike is essentially just a conventional bicycle with add-ons. The front brake is an inexpensive long-reach sidepull, marginal even without the added weight of a motor and battery. The rear wheel has a Shimano three-speed hub with a coaster brake.

Front brake and hub of the Lahaina bike

Front brake and hub of the Lahaina bike

Here’s another example, a Pedego electric bike configured more or less like a conventional bicycle, and with derailleur gears, but with an electric motor in the rear hub, and on its way to be a motorcycle with fat tires that would have unacceptable rolling resistance with pedal power only. The disc brakes should be adequate to their task.

Fat-tire electric bike, with distinct motorcycle tendencies.

Fat-tire electric bike, with distinct motorcycle tendencies.

The e-Solex electric bike shown below is configured more like a motor scooter, with a step-through frame that favors a rider with limited flexibility, or who wears a skirt. The saddle is adjustable upwards, for efficient pedaling. (Note other bike in the background, with raised saddle.) Solex was the classic mid 20th-century French moped add-on, a small gasoline motor that transmitted power through a roller on the front tire of a conventional bicycle. The e-Solex recalls this design, though the motor is actually in the rear hub and the cylinder over the front wheel is a baggage compartment.

An electric bike which is more like a motor scooter

An electric bike which is more like a motor scooter

At the show, there was even one cargo trailer with a motor, that could be hitched onto any bicycle and could help bring home a heavy load.

I didn’t expect to see so many electric bikes at the show. I have thought in the past that adding a motor to a bicycle would inevitably lead to atrophy of the pedals through disuse. Motorcycles began as a subspecies of bicycles in the first decade of the 20th Century. Again, in the mid-20th Century, bicycles with a small gasoline auxiliary motor evolved into mopeds, with vestigial pedals, and into motor scooters, with no pedals at all. Why?

  • The heavier machine with its motor made pedaling ineffective;
  • the motor also made pedaling irrelevant;
  • the motor made higher speed possible, and a larger and more powerful motor, in turn, required a heavier frame;
  • storing a gasoline-powered machine in a living area was not practical.

For these reasons, motorized two-wheelers diverged into entirely different categories from bicycles, with little or no overlap. Electrically-powered two-wheelers never succeeded in the market, as the dead weight of batteries made them more trouble than they were worth – no fun to ride, heavy to carry, with short range.

But now electric bikes have improved substantially thanks to lithium-ion batteries and rare-earth magnets. Concerns about air pollution also come to bear. An electrically-assisted bicycle can be stored in a living area. It can go up in an elevator, though it can’t easily be carried over the rider’s shoulder like a pedal bicycle. Electric two-wheelers have become popular in China (though still using lead-acid batteries there), and the corner may be about to turn in other countries as well, including the USA.

At the dirt demo days at Interbike, people on electrically-assisted bicycles were effortlessly cruising up the steep hill to the demo site in the 99-degree heat. Even in the dry, desert heat of southern Nevada anyone who pedaled up the hill would be wearing a coat of sweat-soaked dust before reaching the top.

There was even a sort of John Henry vs. the steam drill uphill race. Everyone was pedaling furiously, so everyone ended up sweaty, I’m sure. One particularly strong cyclist on a racing bike finished near the front, but a small-wheel, fat-tire electric bike was first.

At Interbike, I spoke with my colleague John Schubert, who suggested that electrically-assisted bicycles would be useful:

  • To allow a person incapable of producing enough power to make use of a bicycle for local transportation. This is obvious enough. With the Baby Boom generation aging, this can be a substantial market.
  • To make short “Dutch-style” utility-cycling and commuting trips possible without a person’s having to work up a sweat – important for many people.
  • To make longer “bigger, hillier US city” trips practical for people who would otherwise only consider shorter trips.
  • To allow a bicycle tourist to cover greater distances or keep up with a group of stronger riders. This is, to be sure, only possible where there are places to recharge overnight — but most campgrounds have electrical power. John tells a story of an elderly man who was thrilled to have participated in a multi-day tour which would have been impossible for him otherwise.
  • And entirely eliminating the complications and extra weight of pedal power, that small, electrically-powered motor scooters, would be practical for short-distance urban travel — and they exist, but they do not yet fit into a legal category in many places.

I would add one more point: that electrically-assisted bicycles will be much more appealing in hot climates than in cold ones. This is mostly a question of rider comfort, but also, battery performance decreases appreciably in the coldest weather. In impoverished countries with hot climates, bicycling of the very slow, energy-conserving variety has been a favored mode of transportation, but has given way to gasoline-powered motor scooters as soon as rising income made them affordable.

Whether electrically-assisted bicycles are going to find an important niche in the US market remains to be seen. Certainly, they are less expensive than mopeds or motorcycles; their environmentally-friendly and indoor-storage-friendly characteristics may appeal — but for the foreseeable future, the power-to-weight advantage lies with the internal combustion engine and its fuel tank.

Wherever electric or gasoline-powered two-wheelers steal a substantial part of the market for utility trips away from pedal cycles, expect some serious dislocation in planning. But that’s a topic for another article.

About the laser bike lane…

Lasers projecting the image of a bike lane from a bicycle onto the street ( Laser — high tech — must be a great idea then? Not really.

Light shining directly from the vehicle toward the viewer is many times more efficient than lighting the road to indicate the position of the vehicle.

A bike lane that moves with the bicycle conflicts with the road markings on the road.

The page: (with the red lines) is a Photoshop job. The beam from the light would have to pass through the rider to illuminate everywhere shown, and there is no pavement texture visible in the lines on the pavement.

The green lines at either side on the page appear to have been generated by a device on the bicycle, but the bicyclist symbol in the middle of the lane looks like a Photoshop job.

The video embedded above and at, [missing from the Web page as of July, 2011] appears indeed to show lines on the roadway projected from a device on the bicycle’s seat post, but not from the device shown on, as the green spots which the light comes from are too far from the centerline of the bicycle. Also, I just gotta love this masterwork of obfuscation:

“Preliminary contextual research shows its performance in real world situations is best when lighting conditions are at their worst, improving safety in the most critical situations.”

That is to say that light output is weak.

Lasers are hugely inefficient, but because they produce a pencil-thin beam, can send all of it into the pupil of an eye and cause retinal burns if bright enough to light the road — especially, green lasers, whose light is absorbed by the red chorion tissue behind the retina. One reflection from a puddle into the pupil of your eye, of a laser above 10 milliwatts in output power, for as little as a few microseconds — boom — retinal burn, if a mechanical scanning device is used to generate a pattern, as is usual, or if the device stops. A hologram might also be used, but it would reduce efficiency. The lines shown do not extend forward of the bicyclist where most conflicts occur. Notice in the picture that the reflective spots on the cyclist’s shoes show brighter than the taillight included in the laser device, when the cyclist is in the car’s headlight beams. To the credit of the promoters, the cyclist is shown using a headlight.

There is only an e-mail address on the Web site for contact information but, judging by the uniquely nonstandard curve-into-curb edge stripes on the roadway, I think this video was shot here in Massachusetts.

And, the bicyclist in the video rides in the door zone and makes a left turn from the right curb on a red light. The car following him also turns left on red. I’m glad I wasn’t sharing the road with these people!

Now, looking at this photo, , I can confirm Massachusetts — the famous Citgo sign near Fenway Park (go, Sox!) is visible in the background.

Right here in Massachusetts! Maybe the perpetrators are associated with a certain educational institution on the Charles River, of which I’m an alumnus! What a thought…