John S. Allen's Bicycle Blog

The dream of an autonomous bicycle is that it would control itself, relieving the rider of the need to know how to control it or ride safely. It would also have an electric motor so it could deliver itself to where it is needed. But the weight, expense and power draw required for the sensors on an autonomous vehicle put them out of consideration for a bicycle. Those problems might be solved with another 20 years of technological progress, but still, how would an autonomous bicycle pick itself up if it fell over? How would it climb stairs, curbs, snowbanks or other obstacles, without someone to carry it?

There is a video of an autonomous bicycle online — as an April Fool’s joke.

There is a project to design what is called an autonomous bicycle at the Massachusetts Institute of Technology — but it is not a bicycle, it is a tricycle.

As described in another post on this blog, metal detectors embedded in the street to trigger traffic signals first appeared around 1970, when transistorized electronics made them practical. By 1986 they were in fairly widespread use, and the definitive report on them, the City of San Diego Traffic Signal Bicycle Detection Study, had been published.

I myself have published on this topic.

Two articles in the June, 1983 issue of Bicycling Magazine, one of which I wrote, describe a fatal crash in California: a bicyclist could not trigger a protected left-turn signal phase. He was struck and killed by a vehicle proceeding straight through in the opposite direction, concealed by another vehicle in the opposite-direction left-turn lane. The protected left-turn phase was supposed to be triggered by a metal detector buried under the surface of the street. The metal detector was not sensitive enough to detect a bicycle. This incident likely prompted the work which led to the San Diego report.

I also posted an article about traffic-signal actuation issues on my Web site in 1993, and have updated it several times since.

The measures described in the San Diego report are easy to implement: they require only a change in the pattern of wires installed in the street, and an adjustment of the sensitivity of the electronic controller. A painted marking to indicate the best place for a bicyclist to wait is desirable with some wiring patterns. No new equipment is necessary. Though there have been many other publications about traffic-signal actuation, adoption of the measure has been spotty.

Here is a selection of current reference materials available online as of November, 2018:

The 2012 edition of the AASHTO Guide for the Development of Bicycle Facilities, section 4.12.5 (page 4-47 ff.) explicitly indicates that

[a]ctuated traffic signals should detect bicycles; otherwise, a bicyclist may be unable to call a green signal and may be forced to break the law by violating a red signal. Various technologies are available for detecting bicycles, including inductive loops, microwave, video, magnetometers, and pushbuttons.

The AASHTO Guide deprecates the quadrapole loop in favor of the diagonal loop, which is sensitive across its entire width and so, does not require a pavement marking .

The Manual on Uniform Traffic Control Devices describes a sign and pavement marking to use in conjunction withe loop actuators.

Portland State University has published a detailed technical report which addresses issues of clearance times etc., Operational Guidance For Bicycle-Specific Traffic Signals in the United States.

Some documents from advocates and local governments, among many others:

• Bikewalk NC description of actuators including newer types (video detectors, etc.)
• City of Santa Cruz, California, description of measures for bicycle actuation
• Not just a problem for bicyclists: “What to do about traffic signals that ignore motorcycles”

Steven Goodridge, North Carolina bicycling advocate and engineer, earlier posted an article describing the technical functioning of actuator loops in terms understandable by a layperson.

In recent years, as described in some of these documents, video detection has become common, though it can fail in the presence of heavy rain, snow or falling leaves. At night, a bicyclist may need to aim a headlight directly at the camera. LIDAR (Light detection and ranging) sends out light pulses to measure the distance as well as the direction of objects, and overcomes the problems with video, but as of yet is expensive and has seen little use for traffic-signal actuation. (It is a keystone tehcnology for driversless vehicles.)

Video and LIDAR vehicle detectors  respond to bicycles which have non-metallic (usually carbon-fiber composite) rims and tires with non-metallic (usually Kevlar) bead wires. Loop detectors do not. This problem should be addressed in product design regulations — the province of the U. S. Consumer Product Safety Commission) by requiring a loop of wire in the rim, but the CPSC has not addressed it.

An article on the UKrant.nl Web site describes an intersection in the Netherlands with simultaneous green lights in all directions for bicyclists. The headline, “How to Survive Simultaneous Greens” misrepresents the installation (not all greens actually are simultaneous) and tends to promote a spirit of support for careless innovation.

The video below appears at the top of the article. The featured still image looks benign enough. When you click on the image to set it into motion you’ll see that bicyclists are crossing at right angles to others, and some are taking odd routes across the intersection.

Alle Richtingen Tegelijk Groen from UKrantvideo on Vimeo.

How to survive simultaneous green lights? Same way we survive any uncontrolled intersection: yield to traffic already in the intersection. Note in the photo that the simultaneous green lights are only for bicyclists, who have special bicycle signals. Motor vehicles are shown waiting for red lights.

There is no legal right turn on red either, so the motorists may not enter the intersection. Bicyclists enter from a narrow channel to the right of the waiting motor vehicles and so the intersection works more or less like a roundabout during the all-green bicycle phase. This treatment solves the problems with right-hook and left-cross conflicts, at the cost of increased delay for everyone because of the additional signal phase.

Couple quotes from the article:

In the subhead; “It might look chaotic, but in fact – it’s the safest way to do things.”

A couple of paragraphs in: “When the city of Rotterdam tried to implement a similar system, there were two accidents in the first two minutes, and the alderman quickly cancelled the experiment.”

If people understand to circulate as in a roundabout, then it is going to be reasonably safe. If not — chaos, of which there is much in the video.

The article mentions two problems in Rotterdam: the intersection was too small, and people weren’t used to it. The article makes no mention of any rules for circulating in this intersection or education in how to use it — essential to improve the survival rate — and I can add, there is no mention either of how pedestrian traffic is addressed. (The video, however, does show pedestrians crossing during the bicycle phase — so the rules for them during the bicycle phase are also the same as in an uncontrolled intersection: cross in any direction at any time, and drivers  — bicyclists — must yield) The claims that this is the safest arrangement is unsubstantiated in the article and undercut by the Rotterdam experience.

Here is another video, of a bicycle roundabout on the campus of the University of California, Davis:

I think that a bicycle roundabout is a valid concept where bicycle traffic is heavy enough and motor traffic light enough to justify it. The Davis installation, which prevents chaos by channelizing the bicycle traffic, is better than the Groningen one, where bicyclists — and moped riders, who also use the bikeways —  ride straight across from one corner of the intersection to another, and take shortcuts that put them into conflicts. Whether that kind of traffic flow could be achieved without physical barriers, allowing heavier motor traffic between the bicycle-only signal intervals, is another question, though.

This video is long on promotion and unbalanced, weak on anything which approaches a description of a comprehensive bicycle program. Parking? Enforcement? Education? Other infrastructure?

0:00 Leads with fear and hyperbole. “Let’s be honest. For many people, the thought of cycling in a city was terrifying.”

0:06 — picture of a door zone bike lane, just like most in NYC, cyclist risks dooring from the left and then is doored from the right. A perfect example of how not to ride. The hazard is obvious to anyone with an elementary understanding, so why did the bicyclist ride right into this trap?

0:24, Picture of a gauntlet, Sadik-Khan says “it was almost like being a cast member from Escape from New York.” Maybe if you were an extreme sport person, it was a great place for you because you were dodging cars (picture of traffic jam, dubbed-in sound of car horns.). Well, yeah, that’s fiction, but as Sadik-Khan uses it, it’s hyperbole.

1:10 “We put down 400 miles of on-street bike lanes.” (Note, all bike lanes are on-street, by definition.) Bicyclist is shown riding in a door zone bike lane, like most in New York, like the one the cyclist at 0:06 was doored in and like the one where a cyclist was killed a few weeks ago when a livery vehicle pulled out, collided with her and dumped her under a truck.

1:20 Claims that the 9th Avenue lane is much less stressful are buttressed by running video clips in slow motion, and with calm music.

1:32 Cyclist is shown avoiding the bike lane.

2:15 Staggered traffic signal timing: The 9th-Avenue bikeway was the first, and well-designed to avoid conflict if everyone obeys the rules, but the video neglects to mention that the staggered timing reduces green time for bicyclists, and the timing still favors motorists (green wave originally at 30 mph, now down to 25 due to city-wide speed limit reduction).

2:20 More slow motion.

2:23 Injury claim is for all users, not bicyclists. This is not stated. “Win” claim is vague, different for each type of user. The win claim for motorists is only that they got a separate turn lane, not that capacity was increased. It was reduced. Claim for bicyclists is of reduced stress, not of reduction in travel time: it was increased. And again, safety claim is an overall claim, not one for bicyclists.

2:50 The 9th Avenue lane was carefully designed. Later ones were done on the cheap without separate signal phases and other amenities. Saying only that more were constructed avoids the issue of their quality.

3:35 “You can’t just paint sharrows on a street and expect that people are just going to, voilà…” Shared lane marking shown is in the door zone.

4:00 Roger Geller’s categories of cyclists are not from a survey. They are a categorization he created out of thin air.

4:25 “If you want to build a better city, you can start by building better bike lanes.” — That’s what the closed caption says. Sadik-Khan says only “building bike lanes.” Conveys that the only thing a city needs to do for bicycling is to build bike lanes.