On Bicycles, and.... what else is there?

In previous post I proposed an algorithm for automated detection of speed limit violations from GPS data . Then in a later post I tested this on simulated data . Here I apply it to data which was collected by someone else during a short drive in San Francisco. I've a general 40 kph speed limit within the city (also previously here ), except on the interstate highways. This car trip didn't include any interstate highways, so it will be interesting to see how it would do with such a restriction. Here's the speed versus time. As you can see, it was a short trip, only around 8 minutes: It's mostly slow going, except for one stretch on Bayshore Boulevard, which is faster. That portion is generally 50 to 65 kph, Sure enough, this triggers the algorithm as speeding for a 40 kph limit. I assign a fine in dollars equal to the excess distance ahead of a "pace car" beyond the 50 meters allowed by the algorithm, at a ratio of one dollar per 100 meters. So if...

Last time I proposed an algorithm for detecting speeding vehicles. In summary, the algorithm was to set an actual speed limit 5% over the nominal speed limit, then compare the car's position to a "virtual pace car" going that speed limit, where the pace car would slow to avoid getting behind the car in question. If the driver got 50 meters ahead of this virtual pace car, he'd be fined proportional to how far ahead he got. If he kept pulling away, the fine would keep increasing. I tried various approaches, but I think the best one is relatively simple. I assume a car starts at rest, then accelerates at 3 m/s 2 (0.31g, or 0-60 in 8.94 seconds) to some final speed, then holds that speed. There's a posted speed limit of 20 meters/second (72 kph), implying an enforced speed limit of 21 meters/second (75.6 kph) which the driver reaches in 7.00 seconds, having traveled 73.5 meters. If the peak speed is no more than 21 mps, the driver is never cited. But if the p...

Last time I argued for automated speed limit enforcement using GPS receivers installed in all new vehicles sold. I would be negligent in doing so without at least proposing an algorithm. So the algorithm is this: Determine the present speed limit. If GPS is used to monitor speed, the GPS coordinates would need to be mapped to a street map to determine a local speed limit. This seems complicated, but in many urban areas the speed limit is the same on all roads in a local grid, so you'd basically just need to identify if the driver might be on an expressway or an interstate based on position and direction. If the speed limit was varying wildly from one road to the next, this would become more complicated, and only the maximum of the local speed limits could be enforced this way. GPS has only a certain position precision. Set a true speed limit 5% higher than the nominal. This gives some margin for error. GPS doesn't have systematic error nearly this large, but it makes se...

San Francisco's Board of Supervisors embraced a " Vision Zero " policy goal which is gaining traction: the goal is for zero pedestrian and cycling deaths within 10 years. It sounds good, but it's a bold goal which demands real action. It's like San Francisco's "Transit First" policy, a part of the City Charter, which states that the pedestrian safety and public transit receive priority over individual motor vehicles. But in the end, there's little evidence this law drives actual policy. Lip service without action reeks of hypocracy, and hypocrisy is in no shortage in San Francisco. "Leland Yee". Nuff said. ' But assuming Vision Zero is serious, there's only one way for San Francisco to substantially reduce the carnage seen on the roadways year after year: reduce vehicle speeds. A classic example: Potrero Ave near Potrero Hill where I live. It's signed for a 25 mph speed limit, appropriate for a road with a school, a...

Governor Brown, after vetoing two, finally signed a 3-foot passing law for the state of California: AB1371 . Hats off Jim Brown and the California Bike Coalition for their dedication and persistance to this issue. It was very much on my mind this year as I experienced several close passes by heavy vehicles. With the status quo of "no blood, no foul", these passes were effectively legal, since what constitutes a "safe pass" is so vague. Here's the text of the bill-now-law, which I'd like to review here. Note I'm an engineer, not a lawyer, so I'm just interpreting the language, without any insight into lawyer-specific knowledge: SECTION 1 . Section 21750 of the Vehicle Code is amended to read: 21750 . (a) The driver of a vehicle overtaking another vehicle or a bicycle proceeding in the same direction shall pass to the left at a safe distance without interfering with the safe operation of the overtaken vehicle or bicycle, subject to the limitatio...

A year ago, Troy Davis was executed for murders he is claimed to have committed, in Georgia. From an article in Time : In the 48 hours leading up to Davis' execution, the nation heard that the case against Davis was built entirely on eyewitnesses who said they saw Davis gun down off-duty cop Mark McPhail. But of the nine witnesses who testified against Davis in his original trial, seven would go on to change their mind and recant. So nine people, who didn't know him, claimed to have seen Troy commit the crime. Seven later recanted, and yet he was still killed by the state. In contrast, there are reportedly ten independent people, each of whom knew him, including teammates, an ex-wife, and an ex-fiancee, testifying that they observed Lance Armstrong either self-administering illegal drugs, or describing his method and practice of doing so. Additionally, Lance is reported to have encouraged others to use these drugs. He left behind blood samples which have been tested by ...

As virtually everyone knows, in March Chris Bucchere, riding a bike over a Strava segment on which it has been reported he was trying to KOM, rode his bike through an intersection in the Castro district, hitting 71-year-old Sacha Hui. Sacha's head hit the pavement, causing an apparently fatal injury (I'm assuming he didn't happen to die of natural causes on the spot). The reaction has been almost of lynch mob proportions. The local news web sites are full of comments raging against cyclist irresponsibility in general, and specifically for Chris to be held to the highest standard of accountability. The San Francisco Bicycle Coalition, when asked about the case, has emphasized that "pedestrians always have the right of way" (which is flatly incorrect), and stresses the importance of riding safely and responsibly. Indeed, recently Chris was charged with felony manslaughter over the incident. Claimed reasons were reports he had run red lights in intersections...

Recently, for Strava, the inevitable happened. It was announced they are being sued . In this case Kim Flint , who was 41, rode his bike down treacherous South Park Road in the Berkeley Hills. That segment was later marked as "dangerous" by a user, but he still has the record descending nearby Centennial Drive . Kim obviously liked to put it on the edge downhill. There's risks with that, and in his case, he lost the bet. The key issue here is what responsibility Strava has for Kim's risk-taking? If I promote a bike race on a course which is obviously dangerous, and people enter the race expecting some degree of safety, then if someone dies in the race I expect I'd be fairly exposed. But the historical standard for bike racing is at a relatively high level of risk. Anyone who's tried to stay with the lead group descending from Hamilton summit in the Mt Hamilton Road Race knows that. But the question in this case is: is Strava acting as an event promot...

Here's the AAA's explanation of why they oppose SB910, the bill which would require a 3-foot passing gap when motor vehicles pass cyclists. Thank you for your inquiry relative to AAA's position on SB 910. Our official position is not a straight oppose, it is an 'oppose unless amended'. We don't take issue with the 3 foot distance rule when it can be safely accomplished. The problem is how to address situations when a 3 foot distance cannot be maintained or met. Current language in the bill would require the vehicle to slow to 15 mph of the speed of the bicycle to pass. But this is problematic for several reasons, as pointed out in the bill analysis, the link for which you provided. Law enforcement has issues with this approach as well because it can cause a drastic decrease in speed differentials between the vehicle passing the bicycle and other vehicles on the road depending on the posted speed limit. Not only can this cause rear-end collisions, and...

A legislative analysis of SB910, the 3-foot passing rule for drivers passing cyclists, is here . Last time I noted that the AAA, an organization which opposes virtually all initiatives to improves cyclist rights, infrastructure, or safety, is the sole listed opponent. Excerpts from comments from the analysis, and my response: Enforcability.... How can either (the driver or a police officer) be sure that the driver is not 3 feet, 3 inches away rather than 2 feet, 9 inches? This argument could strike down almost any law in the vehicle code. If the speed limit is 65, how can I be sure I'm going 64 mph and not 66 mph? If the law required headlights after dusk, how can I be sure it's one minute before dusk and not one minute after dusk? Obviously enforcement carries a burden of proof, and behavior requires a margin for uncertainty. So while 2 feet 9 inches may be questionable, 1 foot 0 inches does not. And it's the really close calls which we care about. Ironically...

The Senate has posted an analysis of SB910, the bill which would impose a 3 foot minimum passing distance for motor vehicles passing cyclists. There is now on AroundTheCapitol an analysis, dated Thursday 28 April. First, I'll jump to the end: SUPPORT : Office of the Mayor, City of Los Angeles (co-sponsor) California Bicycle Coalition (co-sponsor) Amgen Cycling Club Channel Islands Bicycle Club Humboldt Bay Bicycle Commuters Association Sacramento Area Bicycle Advocates Santa Cruz County Cycling Club Silicon Valley Bicycle Coalition 47 individuals OPPOSED : AAA Northern California Automobile Club of Southern California Just in case any cyclists out there are members of AAA, please quit now. Try Better World , for example. AAA members are supporting the AAA's car-centric legislative agenda, opposing every attempt to improve the rights of cyclists on the roads. It is incomprehensible to me that any member of any bike coalition would be also a member of AAA. ...

Yesterday I hit refresh on my screen yesterday morning, and I saw this ( link )... the text of SB910, the bill supposedly requiring a 3 foot passing buffer when drivers pass cyclists, was revised. Changed from: 21750.1. (a) (1) The driver of a motor vehicle overtaking a bicycle proceeding in the same direction shall pass to the left at a safe distance, at a minimum clearance of three feet, at a speed not exceeding 15 miles per hour faster than the speed of the bicycle, without interfering with the safe operation of the overtaken bicycle. To: 21750. 1. (a) The driver of a motor vehicle overtaking a bicycle proceeding in the same direction shall pass to the left at a safe distance, at a minimum clearance of three feet or at a speed not exceeding 15 miles per hour faster than the speed of the bicycle, without interfering with the safe operation of the overtaken bicycle. Wow -- talk about flip flop from replacing a comma with an or. So it's now considered safe to blow by a c...

The California State Senate is considering SB910, the latest in a long-running series of bills requiring a minimum passing margin for cyclists. The text of the bill is here . The key text: 21750.1. (a) (1) The driver of a motor vehicle overtaking a bicycle proceeding in the same direction shall pass to the left at a safe distance, at a minimum clearance of three feet, at a speed not exceeding 15 miles per hour faster than the speed of the bicycle, without interfering with the safe operation of the overtaken bicycle. I'm a huge fan of a 3 foot passing margin. It really changes nothing, since any rational observer would conclude passing with less than a three foot margin is unsafe, and it's illegal to pass at an unsafe distance. But this codifies that less than 3 feet is de facto unsafe, removing the burden to prove it. For example, presently a driver could pass with a two-foot margin, hit a cyclist, then claim it was the cyclist's fault for veering to the left. T...

Sausalito has passed a plan to " ease the bicycle crunch ", including posting signs advising cyclists to "ride single-file". Unfortunately, it's not so simple: cyclists are not required to ride single file, no matter what law makers or enforcers whould like you to believe. Therefore such signs would be misleading. I propose the following, instead: This does a much better job of describing what cyclists must and should do on the roads. Which when you're riding the speed of traffic on a narrow road, has nothing to do with being single-file.

I've been sick the past few days. "Something's going around." But then around here, it always is... I almost don't remember the last time I felt the euphoria of a nice long ride. But on to today's subject. It looks like the Idaho stop may actually have a chance in Oregon . The Idaho Stop is the a law that in general cyclists may treat stop signs as yield signs, red lights as stop signs. Honestly, it's what most people do anyway when they're on a bike. They roll slowly up to a stop sign, check to see if the intersection is clear of cross-traffic, and if it is evident that it is clear, they ride on through without coming to a total stop. Is it always a good idea to roll through stops? Obviously not. Is it true that every time a cyclist rolls through a stop sign they do so responsibly? Obvious not. But then the Idaho law doesn't say it's always okay for cyclists to roll through stops. What it says is (italics mine): 49-720. STOPP...