Showing posts with label law. Show all posts
Showing posts with label law. Show all posts

Sunday, April 27, 2014

testing speed limit algorithm with real data

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:

image

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 the car in question pulls 150 meters ahead of the "pace car" during the trip, that's a $1 fine.

Here's how the fine varies with speed limit:

image

At a 40 kph speed limit, the fine would be $1.74. It goes up substantially if the speed limit is lower. By 49 kph, it drops to zero. Note the car actually got up to 63.2 kph, but not long enough to trigger a speed limit violation between 49 and 63 kph.

At present, a speed fine is viewed as a big deal. You get pulled over, mailed a citation, given a big fine with additional fees, and possibly waste time in court defending yourself. With this system, there would be none of that. You'd get notified of a fine, and you (the registered owner of the car) would pay it by 30 days or whatever. The fine could be big or small. But acceptance of the responsibility to pay assessed fines would be part of receiving the privilege of driving a car. If you don't pay your fines accrued for your car(s), your driving privileges are suspended until you do.

This was just a short trip, so fines tend to be small. But the speed was quite modest over the majority of the drive. The goal here is to eliminate the uncertainty. If you speed to a certain threshold, you'll pay. Such a system would substantially slow the prevailing traffic speed, both increasing safety and reducing congestion. It would make getting around, by foot, bike, or even car safer and easier.

I can't simulate the advantages of reduced speed on traffic congestion here, but I can calculate, at the same level of congestion, how much longer the trip would have taken with a 40 kph speed limit cap. That's 24.8 seconds, taking the trip time from 8:36 to 9:00.8. In the spectrum of factors which contribute to delays in getting to a destination, that's a very small number, and it wouldn't take much improvement in traffic smoothness to take it to zero.

Friday, April 4, 2014

simulating vehicle speeding detection algorithm

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/s2 (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 peak speed is in excess of this, he will eventually be cited. The key question is how quickly this happens, given my 50 meters-ahead-of-pace distance criterion.

Here's a plot of the time taken for the speeding indicator to trigger. For the 22 mps peak speed, only 10% over the nominal speed limit, it takes 53 seconds before the 50 meter threshold is reached. For the highest speeds more of the time is taken by the acceleration phase after the 21 mps threshold is crossed, and the time hits a limit of approximately 8 seconds.

time to speeding

The other statistic of interest is how much distance was covered before the threshold was reached. This is easy to estimate from the time: the "virtual pacer" goes 21 meters each second, so add to that distance the 50 meter threshold and you have the distance covered by the perpetrator. The result isn't exact because of the requirement three points in a row are over the distance threshold, so the final margin may well be more than 50 meters, increasing the net travel distance.

Here's that plot, with distances taken from the simulation, not the estimated calculation:

distance to speeding

It's around 1180 meters in the case of the 22 mph speed, decreasing to around 250 meters at the highest speeds.

200 meters is typical for a city block, so the algorithm won't catch a violator in a single block for this 20 mps (72 kph) speed limit. But a more typical urban speed limit is 40 kph or even 30 mph. With the "virtual pacer" going slower, it's possible the 50 meter threshold could be reached in a single block. But more likely is to get caught traveling over a longer distance, for example two blocks connected by a green traffic signal.

Here's an example of a randomized speed schedule, where the driver is averaging 20 mph, equal to the assumed speed limit:

random speed

It takes around 20 seconds for the driver to go from the 20 mps speed limit to 25 mps, at which point he triggers the speeding threshold. Then the speed decreases, eventually back below the speedlimit, and the "excess distance" decreases, eventually back below the 50 meter limit.

So the criteria I propose are fairly strict, yet only marginally strict enough to catch someone speeding along a single city block. Yet I stand by the strictness. If you don't want to be fined don't go over the speed limit. When you do could be the time you kill someone.

The one key point here is when the speed limit changes. A way around this is to extend the boundaries of the higher speed limit somewhat, to give drivers a safety margin, relative to where the higher speed limit is marked on the roadway.

Thursday, April 3, 2014

proposed automated speed limit enforcement algorithm

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:

  1. 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.
  2. 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 sense to have a small buffer if you're going to be fining people.
  3. Set a distance threshold. If you pop over the speed limit for one second, that shouldn't be fined. GPS has a finite position accuracy, for example 10 meters under the best of conditions, and you want the threshold to be sufficiently above this threshold. On the other hand, if the threshold is too large, streets like Potrero Ave where peak speeds in excess of the speed limit are not typically sustained for long due to frequent traffic lights will go essentially unenforced. So I'll propose 50 meters for this.
  4. Set an acceleration threshold. GPS can sometimes jump due to reflections off mountains, building, etc, yielding an essentially instantaneous displacement of position. These jumps should be ignored. So if the position jumps in a way inconsistent with the operation of a realistic motor vehicle, that should be ignored. This can be checked as follows. For any 3 points, p1, p2, and p3, with sampling times 0, 1, and 2, if p2 deviates from the average of p1 and p3 by more than 10 meters, then the interval from p1 to p3 is assigned a speed equal to the true speed limit.
  5. Maintain an integral equal to the accumulated distance in excess of that which would be traveled at the true speed limit. So for travel from p1 to p2 over time Δt, add ( p1 − p2 ) − vmax Δt to the excess distance. Excess distance may increase or decrease, but it is limited to zero if it would be reduced below zero. At the start of a trip, it's zero.
  6. If the car is in excess of the maximal allowed excess distance continuously over some period, for example 3 seconds in one-second samples (to allow time for checking the points as described above), the registered owner of the car is fined proportional to peak excess distance sustained over a 3 second period.

Note there's plenty of slop in this approach. First, the true speed limit is set higher than the nominal speed limit. Then the driver must get a certain threshold above a "virtual pace car" going at the true speed limit. Then he must stay beyond this threshold for a certain period of time. Additionally, the "excess distance" is unchanged if the GPS data are suspiciously inconsistent. All in all this would create a challenge for automated enforcement on urban roads.

For urban settings, fixed-point speed monitors would thus still be required. A video camera in conjunction with sonar, for example, can identify vehicles moving quicker than the speed limit. These are not presently used for automated speed limit enforcement, but with a change in state law, that could be changed.

This proposal is not in any way a threat to individual liberty. Driving is not a right, but walking is, and there is no greater denial of liberty than to create conditions where someone can't walk across their street safely. By driving in a way which compromises safety you are depriving others of their fundamental right. So this is about preserving rights, not denying them.

I'll show a simulation next time.

Wednesday, April 2, 2014

San Francisco Vision Zero: vehicle speed

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 hospital, and a large number of homes. But the 25 mph posted limit is a farse. Speeds more typically exceed 40 mph on the road, popular as a bypass for Interstate 101 when the freeway is clogged at Hospital Curve, which is often.

Another example: San Francisco has dense grids of streets where traffic is typically halted every block by stop signs or traffic signals. These blocks are short. Yet it's common for drivers to floor the accelerator, then slam on the brakes just in time to slow to what they perceive is a reasonable imitation of stopping. Such neck-snapping accelerations and decelerations do little to reduce travel time but do a lot to increase fuel consumption and reduce pedestrian safety. Really it's driven more by testosterone than rational thought. These people need to get out of their cars and exercise more. Then they'd have a healthier outlet for their aggression.

People like to talk about the three E's: Education, Enforcement, and Engineering for public safety. The Education part is no-brainer: the speed limit is as fast as you should go. That's simple enough. That's not working so well. Engineering suggests traffic calming, but it's prohibitively expensive and slow in the bureaucratic quagmire which is San Francisco. The real key is enforcement. But the present model for enforcement is not the solution. Police are paid with salaries well in excess of $100k per year, with generous benefits and pension programs no public sector industry can come close to affording. They're expensive, to put it lightly. And they have little interest in spending their time flagging down ubiquitous speeders. They consider themselves overqualified for such mundane tasks.

So we need another way.

That way is obviously automated enforcement. If your car exceeds the speed limit by some combination of speed and time, a citation goes to the registered owner of that car. That's it. Do that, and speeding will disappear virtually immediately.

The problem is the law won't allow for such a policy. First, the speed limit is restricted by the interpretation of the "prima facie speed law", which says that traffic isn't allowed faster than the maximum safe speed "as determined by a traffic survey". The problem is that's interpreted to mean the prevailing speed of traffic, which is measured by the 85th percentile speed determined in traffic surveys. That means if 20% of the cars on Potrero Ave are doing 50 mph in the 25 mph speed zone, then you can't be ticketed for doing 40 mph in that 25 mph zone, whether or not that speed is compatible with Grandma in her walking getting across the road alive.

So for safety-driven speed limits to be enforceable, the 85th percentile rule, in place due to car-loving Southern California, needs to go. This law is based on a more universal engineering principle which should also be retired.

Next is the rule that the driver of a vehicle needs to be positively identified in order to be cited. This rule is inspiration for hit-and-run drivers across the state to hit the accelerator after they run down pedestrians and cyclists. Even if their car is ID'ed, if they can provide a reasonable doubt they were driving, they not only avoid criminal charges, but keep their driving licenses. That needs to end. If you have a registered car, as is the case with a registered gun, you have responsibility for fines accrued by users of that car. This is already the case in Europe, for example, and it's already the case for bridge tolls and parking violations. Driving is a privilege, not a right. That means for traffic citations, the standard of proof is not the same as it is for misdemeanors and felonies. If you're car is speeding, you should be held accountable.

Then there's the speed limits themselves. In San Francisco, a compact city with dense population, there's simply no good reason for cars to be driving in excess of 25 mph except on the freeways which nature hasn't had the wisdom to destroy yet (the 1989 Earthquake did SF a huge service by taking out the Embarcadero Freeway. A targeted strike on 280 would be even better). The difference between 40 mph and 25 mph for a 7-mile drive across the city, assuming that speed can be maintained for half the distance (the other half of the distance congestion-limited) is 3 minutes and 10 seconds. Thats it. That's a very small price to pay for the huge safety advantages of a 60% reduction in vehicular kinetic energy associated with that speed reduction. So a city-wide 25 mph speed limit is appropriate. Even 25 mph is 5 mph more than the "20 is Plenty" program in London.

Unfortunately this all requires primary action from Sacramento, the legislative capital of California. But San Francisco's state legislators should be leading the call.

Automated enforcement is already applied to commercial vehicles in Germany, for example. This is a good start, because if the commercial vehicles were going 25 mph on Potrero Ave, it would be hard for private vehicles to go much faster. Germany uses speed sensors attached to the axles for this purpose, sort of like old-style bike computers which use magnets to measure wheel rotation. But with GPS technology having reached a cost level of 10's of dollars, it would be easy enough to require new vehicles sold in the US to monitor their speed with GPS as well as a black-box function to provide evidence for behavior in the seconds leading to a crash. The conspiracy theorists would go ballistic at this suggestion, arguing the government would be monitoring their travel. First, government is too incompetent to monitor much of anyone. Look at 9-11. Second, the remedy is simple: take public transit, ride a bike, take a taxi, walk... there's other ways to get around without a personal motor vehicle

So this is the sort of seriousness Vision Zero needs if it's not going to be the usual "cost of doing business" road carnage into the forseeable future. I honestly don't believe there's the political will to do it, but I hope I'm wrong.

Friday, September 27, 2013

California 3-foot passing law at last

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 limitations and exceptions set forth in this article. (b) This section shall become inoperative on September 16, 2014, and, as of January 1, 2015, is repealed, unless a later enacted statute, that becomes operative on or before January 1, 2015, deletes or extends the dates on which it becomes inoperative and is repealed.

This seemed an awful like the existing code, so I checked that:

21750. 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 limitations and exceptions hereinafter stated.

So it's exactly as it was before until September 16, 2014. So good luck everyone. I hope you survive the next year.

Then things change for the better.

First, 21750 is fixed so it refers only to vehicles: the word "bicycle" is removed (bicycles are not vehicles in California). This is clearly because the "safe distance" language is no longer sufficient for passing bicycles. "Safe" implies "no blood, no foul", which is realistically the present standard. Indeed, even a collision doesn't imply a pass wasn't "safe" under current enforcement.

SEC. 2. Section 21750 is added to the Vehicle Code, to read: 21750. (a) The driver of a vehicle overtaking another vehicle proceeding in the same direction shall pass to the left at a safe distance without interfering with the safe operation of the overtaken vehicle, subject to the limitations and exceptions set forth in this article. (b) This section shall become operative on September 16, 2014.

In the present code, there's 9 sections which follow 21750, providing exceptions: 21751 through 21759. These remain as-is. 21760 is added, as follows:

SEC. 3. Section 21760 is added to the Vehicle Code, to read: 21760. (a) This section shall be known and may be cited as the Three Feet for Safety Act. (b) The driver of a motor vehicle overtaking and passing a bicycle that is proceeding in the same direction on a highway shall pass in compliance with the requirements of this article applicable to overtaking and passing a vehicle, and shall do so at a safe distance that does not interfere with the safe operation of the overtaken bicycle, having due regard for the size and speed of the motor vehicle and the bicycle, traffic conditions, weather, visibility, and the surface and width of the highway.

So far it really doesn't change much. The "due regard" language should be obvious to anyone who's ridden a bike as an adult. Unfortunately too many police officers, traffic clerks, district attorneys, etc, seem to have no clue about cyclists rights to road, or the realities of riding a bike on the road. This language makes it explicit that the enumerated factors must be considered in establishing a safe passing distance, and therefore the driver can be found at fault for passing with what under ideal circumstances might have been a safe margin.

(c) A driver of a motor vehicle shall not overtake or pass a bicycle proceeding in the same direction on a highway at a distance of less than three feet between any part of the motor vehicle and any part of the bicycle or its operator.

This is good. Note the "3 foot margin" applies to any part of the cyclist or bike, not just the bike, not the center of mass of the rider or bike. So this is a good margin. There is the question of what would happen if a driver were passing a cyclist with a 3 foot gap, then the cyclist were to reach out with a hand and reduce the gap below the 3-foot limit. Would that result in the driver being in violation of the law? I think the answer is the driver should leave a buffer over 3 feet to prevent that from occurring.

In the bill from 2011, there was a provision which removed the 3-foot requirement when the car was below a certain speed limit. This was essentially necessary due to the situation near intersections, where typically cars and cyclists are in close proximity. Brown vetoed that version due to what was clear confusion over this quantitative speed threshold (arguing drivers would slam on their brakes and be rear-ended so they would be able to pass a cyclist with a less than 3-foot margin). So instead of a quantitative exemption, there's a fuzzy one:

(d) If the driver of a motor vehicle is unable to comply with subdivision (c), due to traffic or roadway conditions, the driver shall slow to a speed that is reasonable and prudent, and may pass only when doing so would not endanger the safety of the operator of the bicycle, taking into account the size and speed of the motor vehicle and bicycle, traffic conditions, weather, visibility, and surface and width of the highway.

I was initially opposed to fuzzy language, since it takes us back to the "no blood no foul" status quo. Any sub-3-foot pass could be justified on the basis that the "driver was unable to comply". But at least it doesn't provide a simple exemption: it further requires the driver "slow to a speed that is reasonable and prudent", which strongly suggests a typical high-speed buzz cut wouldn't pass muster. This is followed by some fairly strong language about not endangering the safety of the rider, taking into account the previous stuff, including the "width of the highway". So perhaps this language doesn't render the bill impotent, after all.

But a point of weakness of this law versus the previous bills is the removal of the provision formalizing what virtually every driver does when passing cyclists on a 2-lane road with a double yellow line: cross the line. It's obviously safe. Without removing this allowance, which is justified by the fact double yellows are put in place based on the much more dangerous and time-consuming maneuver of passing a full-size motor vehicle, a driver could still close-brush a rider, arguing that it would have been illegal to tough the double yellow even when there's clean line-of-sight ahead and no oncoming traffic. Fortunately drivers are sufficiently scofflaw that they typically ignore the inane double-yellow law, placing safety first.

Here's where it gets really tragic:

(e) (1) A violation of subdivision (b), (c), or (d) is an infraction punishable by a fine of thirty-five dollars ($35). (2) If a collision occurs between a motor vehicle and a bicycle causing bodily injury to the operator of the bicycle, and the driver of the motor vehicle is found to be in violation of subdivision (b), (c), or (d), a two-hundred-twenty-dollar ($220) fine shall be imposed on that driver.

$35 for endangering human life? That's beyond a joke. Even if the driver causes "bodily injury" the fine is only $220, which could be contrasted to the $1000 fine for littering. Stuff like this makes me wish California would split into two. I want nothing to do with the Southern California motorheads responsible for these low fines, a result of negotiations during the 2011 bill.

Then there's that date again: nothing for a year:

(f) This section shall become operative on September 16, 2014.

Then the money thing:

SEC. 4. No reimbursement is required by this act pursuant to Section 6 of Article XIII B of the California Constitution because the only costs that may be incurred by a local agency or school district will be incurred because this act creates a new crime or infraction, eliminates a crime or infraction, or changes the penalty for a crime or infraction, within the meaning of Section 17556 of the Government Code, or changes the definition of a crime within the meaning of Section 6 of Article XIII B of the California Constitution.

So that's it. If I had to rate it 0-5, I'd give it a 3. I'd really really have preferred it with the double-line-crossing language. And I also think allowing drivers to pass cyclists with less than a 3-foot buffer without an explicit speed limit for that sort of pass is insane. But CalBike tried, not once but twice, and the Governor rejected both times. I'll take what I can get. It is a lot better than status quo. I just need to make it through the next year until the 3-foot limit goes into effect.

Wednesday, September 5, 2012

Lance Armstrong and the Death Penalty

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 two independent agencies for illegal drugs. He has tested positive for cortisone. Activegan, an illegal doping agent which Tyler Hamilton claims they injected into their veins, was found in the team trash bins. He is reported to have tested positive for EPO for which he bribed the UCI to cover up. He is on record having made substantial money payments to the UCI as "donations". Approximately 90% of the top ten riders in each of the years he won the Tour have been involved in doping scandals or rode on teams for which systematic doping has been determined to have been practiced. The rate at which he climbed hills was unprecedented in the prior history of cycling, or in the history of cycling since. In short, the evidence against Armstrong makes the evidence against Troy Davis look flimsy.

Here's an excellent review by Laura Weislo of CyclingNews of reports on the Lance Armstrong doping scandals and on evidence which has been explained away.

Yet despite this, a group of California senators are calling for the USADA decision against Armstrong to be "reviewed". There's insufficient evidence, they claim. He "never tested positive" they say.

I think it's a sad, sad, state of affairs when our representatives in government hold apply a far higher standard of evidence to sports results than to application of the death penalty. Of course, being rich and white versus poor and black is a huge factor here. They come across as total buffoons. It's unfortunate, because among the authors of the letter is Alan Lowenthal, who championed the 3-foot passing bill which has recently passed the legislature and is awaiting Governor Brown's signature. Clearly he has time on his hands now that this important work is done.

Tyler Hamilton's book is released today. Maybe he should send a copy to each of these senators.

Wednesday, June 27, 2012

Chris Bucchere manslaughter charges

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 prior to the collision, that the video had shown him in an aerodynamic position riding into the intersection, and that he'd later posted to the Mission Cycling email group that he had been going too fast to stop. He even posted Strava data showing a reported speed of 35 mph near the intersection. Those data were subsequently removed from Strava (unfortunately I didn't pull them down when they were available).

Then recently, a blog was posted to Bicycling Magazine, Getting the Story Straight. I posted a semi-rambling comment, which I'll reproduce (with fewer typos) here.

As was reported by the SF Chronicle, the video showed the pedestrians and cyclist entered the intersection at the same time. The cyclist entered on yellow. There’s a two-second all-red phase before the pedestrian light turns white. That means the pedestrians entered the intersection at least two seconds early. This is common practice, as videos on this blog post show. Indeed Google maps satellite shots show it’s around 35 meters across that intersection. If the cyclist was going 35 mph, it would take only 2.2 seconds for him to cross. With a 2-second all-red phase, even if the cyclist hit the intersection with only 1 millisecond left on yellow, the pedestrians entering after the programmed 2-second delay would need to instantly teleport to fill the whole cross-walk, since Chris reported there were no gaps available.

And even it this is wrong, even if he was going half the speed and it took him four seconds instead of two, and even if you don't believe the video evidence that the pedestrians entered at the same time Chris did, even ignoring all of these things pedestrians are still required to wait for vehicles which entered the intersection legally to clear the intersection before they enter, whether the pedestrian light is white or not. So I think it's more than safe to say the pedestrians illegally jumped the light.

The video could be used to assess his speed. But the only data I’ve seen reported is from the Strava data uploaded from his iPhone. iPhones are notorious for the poor quality of their GPS data. And if you are trying to determine speed, you need two, not just one, precise GPS point. He was clearly going fast, no doubt, as his riding position shows, and I don’t defend going fast in that intersection. But the issue here is the prevailing standard of manslaughter, not my or your opinion of proper behavior.

I very much doubt if you took a radar gun to cars driving there you’d wait long before finding one matching Chris’s speed, whatever it actually was. Indeed the district attorney was recently quoted by Streetsblog : the reason so few drivers are charged in pedestrian injuries and fatalities is that “in the majority of those cases, unfortunately, the pedestrian has been the one deemed to be at fault.” He was speaking about car drivers, not cyclists. When it’s a cyclist, apparently, even when the pedestrian is proven at fault, as he is in this case, the cyclist gets the book thrown at him. If it had been a car entering the intersection at 30+ mph, and pedestrians jumped the light by over two seconds, the comment sections of the paper would be full of “crazy pedestrians!” comments, not calls for publicly hanging the driver. After all everyone nudges the speed limit when driving, right?

So if the cyclist was behaving like a typical car here, why don't cars pick off pedestrians on a daily basis at that intersection? The reason is, as this blog post noted, pedestrians are programmed to look and listen for cars, while less trained to look for cyclists. That doesn't change the legal obligation to do so, however.

I understand the desire to promote safe and courteous riding. I recognize cyclists, like drivers, like pedestrians, like virtually any pupulation sample, are often guilty of rude and risky behavior. But when discussing “facts”, it’s important to get them straight. In this case, there’s fault to go around. And if we’re going to hold road users to an elevated standard, which I support, it’s important to start with motor vehicles.

Thursday, June 21, 2012

Strava: the Flint lawsuit

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 promoter in this case? Strava's position is likely that they are simply recording and quantifying data that is willingly provided, extracting times over user-defined segments. They use graphical medallions for riders who rank near the top for each segment, which suggests reward, but is it really a case of them encouraging riders to go fast? And if they are, is that a problem?

To answer this for myself (I'm not a lawyer so have to do the best I can) I refer to the California Vehicle Code. Strava has a multi-national customer base, but they're based in California, so this seems a reasonable choice.

Here's a link to section 23109 of that code. A key portion is as follows:

23109. (a) A person shall not engage in a motor vehicle speed contest on a highway. As used in this section, a motor vehicle speed contest includes a motor vehicle race against another vehicle, a clock, or other timing device. For purposes of this section, an event in which the time to cover a prescribed route of more than 20 miles is measured, but where the vehicle does not exceed the speed limits, is not a speed contest.

The key language here is "motor vehicle". When this term is used, it explicitly excludes human-powered transport. Bicycles are subject to "applicable" portions of the vehicle code (even though they're not defined as vehicles) but "motor vehicle" portions don't apply. Usually the code refers to "vehicles" without the motor part.

So what this says is under the law I can challenge my friends or whomever to an informal bike race whenever I want, as long as no other sections of the code are being violated. The code is full of provisions like "exercise due care" so reckless behavior is generally disallowed, but riding uphill is usually no problem, or on open flat roads.

So if I want to "challenge my friends" to a "contest of speed" on my bike, that's fine. It's not fine on motorcycles or cars. People have been comparing times on roads for the full history of the bicycle. People have been blasting down hills as long as I can recall. Strava hasn't changed the existence of informal competition; it's just facilitated it.

Strava does host competitions they initiate, however. These competitions are never for the fastest time descending dangerous roads. They're typically who can climb the most feet, or ride the most miles, or do a climb from a famous race the fastest. There was no such contest for South Park Drive, obviously. If Kim tried to go fast on South Park, it was by his own choice. The irony is if he were still alive I'm sure he'd be the first to deny Strava had any liability in his crash. The last thing he'd want is for the future of Strava, which he obviously loved, to be put into jeopardy by liability concerns. This is a nakedly cynical move by his family to exploit his tragic death, at the expense of an activity he obviously loved. People have been dying on bikes since 1842. They will continue to do so, whether or not they're subscribed to Strava. This is unfortunate, but it's a risk we willingly take every time we get on our bikes. On the other hand, Strava should think twice before opening a category for motorcycles... but they've known this all along.

Sunday, May 8, 2011

AAA position on SB910

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 create a more dangerous situation for the cyclists. It is the differences in speed that is the number one cause of car crashes. Another suggested approach is to require the car to enter into the opposite lane of traffic (cross a double line) in order to give the cyclists the 3 foot distance. This is something being explored as well as a number of other ideas.

While we can all agree on the concept and goal SB 910, crafting workable legislation usually requires addressing a number of details and issues that arise throughout the process as the concept is flushed out and enforceability is addressed. The author of the bill, Senator Lowenthal, is committed to working with all interested parties, including law enforcement, AAA and the bicycle coalition sponsors of the bill to find the most appropriate and safest way to address situations when the general rule to allow a 3 foot distance cannot be met due to road design. We have to determine what the law should be in those circumstances and there is some disagreement on that level. Thank you again for allowing us to explain our position on the bill.

Paula LaBrie
Legislative Counsel
AAA Northern California, Nevada & Utah
Office (916) 443-2577



I generally agree with the letter of Paula's points. However, the mention of "enforceability" is troublesome. As I've already pointed out here, no law is going to be perfectly enforceable, so to hold this bill to a standard of unambiguous enforceability is overly restrictive.

Additionally, the comment that the sponsors of the bill need to "find the most appropriate and safest way to address situations when the general rule to allow a 3 foot distance cannot be met due to road design" is just plain scary. I have the solution to this problem: if the roadway does not allow a pass with a three foot margin then the roadway does not allow a safe pass and the driver must wait until it is safe to pass. The bill is premised on the assertion passing with less than a 3-foot margin is inherently unsafe, at least when the vehicle is going at least a certain speed (for example 15 mph). Therefore making exceptions to a 3-foot passing margin based on the context of road design is equivalent to making exception to a safe passing requirement, and there is no exception made to the safe passing requirement. This bill changes nothing unless you think passing with less than a 3-foot margin can be done safely.

So I wish the question would be put to anyone taking positions against the bill: "do you think passing with less than a 3 foot buffer can be safe?" Unless the answer is yes, spoken with a straight face, there is no longer any margin for debate.

Sunday, May 1, 2011

SB910: bill analysis

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, this very comment justifies the need for the law. If a driver can't judge his distance from a cyclist, then obviously passing margins closer than 3 feet are unsafe.

Is three feet always "safe ?" By defining safe distance as three feet, this bill resupposes that three feet is always a safe distance.

This comment exhibits profound ignorance of the principles of the vehicle code. If the speed limit on a road is 45 mph, that does not mean it's always safe to drive 45 mph everywhere on that road. This argument is so flawed, so twisted, that I immediately question the partiality of Jennifer Gress, the analyst.

The committee may wish to consider an amendment to delete the 15 mph (speed differential) provision from the bill.

Here we completely agree. Change it to an absolute speed instead of a differential speed and I am okay with it to handle the shuffle which occurs at intersections. But the 15 mph speed differential component of the bill is bizarre.

I include the full comment on the crossing the double yellow line provision:

Crossing double solid lines . Double solid lines are put in place when traffic engineers determine that characteristics of the roadway make it unsafe to pass. Does allowing a vehicle to cross these lines create an unsafe driving situation? The author argues that a bicycle is moving much slower and requires less clearance than another motor vehicle and thus would not pose the same risk. Others argue that crossing double solid lines when passing a bicyclist is already a matter of practice for some motorists.

Yesterday I rode along Highway 1 north of Stinson Beach, a 2-lane section with relatively light traffic, good sight lines, narrow shoulders, and a double yellow line. I was passed by several cars, each one crossing the double yellow without the slightest issue. Had a car attempted to pass without crossing the double yellow it would have been unsafe: the passing margin too small.

The double yellow is put in where it is unsafe to pass another car, a maneuver which requires moving fully to the opposite lane and accelerating to a speed significantly faster than car travel speeds. Crossing a double yellow while passing a cyclist requires overlapping the opposite lane by at most the passing margin, presumably 4 feet or so. The two actions are of a completely different class. Sure, we could define 3 sets of road markings: dashed for passing anyone, solid for passing nobody, or a special marking for passing cyclists, pedestrians, and equestrians but not cars. But this of course gets silly. The law relies on driver judgement for when it is safe to cross the double yellow for passing cyclists. Driver judgement is used all the time: for example in judging when it is safe to pass with a dashed yellow line. "Some motorists?" Virtually all, at least 98%, of drivers cross the double yellow in these circumstances. Codifying the typical practice, obviously safe by the standards of vehicular behavior, only makes sense and opponents pulling the safety card on this one is nothing short of hysteria.

Passing on the left only ?

This is an excellent point, and one I had noticed as well. When the cyclist is on the left preparing to turn left, obviously cars need to be able to pass on the right.

Saturday, April 30, 2011

SB910: supporters and opponents

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


AAAJust 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. It's like chasing down your own teammates in a bike race.

This happens time and time again: every initiative to improve cyclist rights, cyclist safety, is opposed by AAA. Recently they fought to get Federal transportation infrastructure dollars more focused on highways, less on trains, less on cycling infrastructure. Every dollar sent to them is supporting their pro-car agenda. AAA is, like it or not, a political lobbying organization, and if you sign on to their free maps or insurance or whatever then you're signing on to their agenda.

On the other hand, hats off the the organizations supporting this legislation. In particular, I'm glad to see Silicon Valley Bicycle Coalition there, and disappointed to not see San Francisco Bicycle Coalition. SFBC, to be fair, is focused on city issues. However, I would have liked to see them step up and show support for such an important state-wide effort.

Friday, April 29, 2011

SB910 gutted?

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 cyclist riding 20 mph going 45 mph within one foot of the rider? Now it's clearly too weak.

Not to mention the penalty has been substantially reduced, from felony to a $220 fine. We're not talking petty infraction here: the key text is "causes great bodily injury".

(b) If a person operates a motor vehicle in violation of subdivision (a) and that conduct proximately causes great bodily injury, as defined in subdivision (f) of Section 12022.7 of the Penal Code, or death to the bicycle operator, the person driving the motor vehicle, upon conviction, shall be punished by imprisonment in a county jail or in the state prison. (b) A violation of subdivision (a) is an infraction punishable by a fine of two hundred twenty dollars ($220).

One plus: Joe Simitian used to run a "It outta be a law" contest in which citizens could submit proposed laws to him which, if it won the contest, he would file as a bill. Mine, allowing cars to cross double-yellows up to 3 feet if there was sufficient visibility when passing "non-vehicular road users" (cyclists and pedestrians), lost out to a "mandatory running of windshield wipers" bill (which passed). A similar provision was added here, at least for cyclists:

(applying to double yellow lines)
(2) As provided in Section 21460.5. (c) (1) Either of the markings as specified in subdivision (a) or (b) does not prohibit a driver to whom any of the following applies from crossing the marking (A) The driver is on a substandard width lane, passing a person riding a bicycle or operating a pedicab in the same direction, and it is safe to do so.

So the 3-foot passing bill is now too weak: the penalty would too small and the 15 mph exception is too broad. If we're going 35 mph, it would okay to have a car pull next to me @ 0 mph delta and pull within 1 foot? Silly. But I'm glad to see the proposed rule allowing cars to cross the double yellow when passing cyclists. I (when I drive) and 98% of drivers do that already.

The whole speed differential thing really should go, though. I'd be willing to support it if it said the car was going no faster than 15 mph, period, no differential, to handle the turbulent conditions near intersections, but even then something a bit slower would be better.

Tuesday, April 26, 2011

SB910: 3 foot passing zone

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. The 3-foot margin gives the cyclist some breathing room.

Of course, it could be argued if a 3-foot margin is necessary to deal with unforseen circumstances, like the cyclist hitting an object on the road and swerving two feet to the left, then the law would actually require an anticipated 6-foot margin, to give the driver a 3 foot margin to avoid the 3-foot margin and therefore a violation. But this is perhaps being picky.

However, what I don't like about this bill is the 15 mph speed difference. It's simply impractical. Bikes are allowed on certain shoulders of I280, for example. Shall all passing traffic slow to 25 mph to accommodate a 10 mph cyclist? The fatal flaw is that the safe passing speed is actually a function of the gap. Perhaps with a 3 foot margin, a 15 mph differential is recommended. But then with a 4 foot gap, the speed can be higher, and with a 5 foot gap, higher still. The law doesn't recognize this: it simply places a 15 mph speed differential limit, even if the car is all the way into the opposite lane.

So I view this presently as bad legislation. I have been told by a member of the California Bicycle Coalition that an attempt will be made to clean this up. Nobody seems to know, I was told, how that 15 mph differential item got into the bill. Given that it's been there for several months, I don't know what's taken so long. It's so obviously flawed.

I really hope this one gets cleaned up and sent through. The arguments against it, that a 3-foot passing requirement will unduly slow traffic, are absurd because they imply, without explicitly stating, that it's acceptable to pass a cyclist closer. As it stands, it's simply too hard to prove a pass was "unsafe". With this bill you'll simply need to prove the pass was closer than the 3-foot margin.

Friday, April 24, 2009

New bike signs in Sausalito?

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:
21202A sign
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.

Monday, April 6, 2009

Idaho Stops

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.

Stop!

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. STOPPING -- TURN AND STOP SIGNALS.
(1) A person operating a bicycle or human-powered vehicle approaching a stop sign shall slow down and, if required for safety, stop before entering the intersection. After slowing to a reasonable speed or stopping, the person shall yield the right-of-way to any vehicle in the intersection or approaching on another highway so closely as to constitute an immediate hazard during the time the person is moving across or within the intersection or junction of highways, except that a person after slowing to a reasonable speed and yielding the right-of-way if required, may cautiously make a turn or proceed through the intersection without stopping.
(2) A person operating a bicycle or human-powered vehicle approaching a steady red traffic control light shall stop before entering the intersection and shall yield to all other traffic. Once the person has yielded, he may proceed through the steady red light with caution. Provided however, that a person after slowing to a reasonable speed and yielding the right-of-way if required, may cautiously make a right-hand turn. A left-hand turn onto a one-way highway may be made on a red light after stopping and yielding to other traffic.
(3) A person riding a bicycle shall comply with the provisions of section 49-643, Idaho Code.
(4) A signal of intention to turn right or left shall be given during not less than the last one hundred (100) feet traveled by the bicycle beforeturning,owing to a reasonable speed and yielding the right-of-way if provided that a signal by hand and arm need not be given if the hand is needed in the control or operation of the bicycle.


For some reason, Idaho has been able to live with this law for 27 years without carnage. Now Oregon is once again proving it is more enlightened than its southern neighbor by treating the idea seriously. The idea of an Idaho stop was floated in San Francisco last year, and the response was a spew of frothy rage. Some of the sentiments:

  • "Cyclists don't deserve to be rewarded with special favors as they show disrespect for the law": First, "cyclists" are not an autonomous group, "cyclists" are people, like all people, who happen to be on bicycles. And among people as a whole respect for the law, sorry to say, isn't very high. How many of these critics report their inter-state purchases and pay the mandated sales tax every April 15? How many cross streets only at cross-walks? How many double-park their obscenely oversized vehicles at church every Sunday? The list goes on.
  • "If you give them a little, they'll take even more." I have never seen any evidence for this. If anything, unreasonable laws breed contempt for the law, not increased compliance. As I just noted, people don't respect the law, they (hopefully) respect each other, and respect more general rules of social conduct. When the law deviates from these general principles, people tend to view the law as silly, and pay it as little respect as they feel they can get away with. What are these rules of social conduct? On the roadways, I'd say they are to be safe, respectful, and predictable. Within this restriction, people then wish to get where they're going as quickly and easily as possible. Really, traffic laws are all designed to promote respect, predictability, and safety. If they fail to do so, they should be fixed.
  • "It's only fair the same rules apply to bicyclists as to cars": This is really dumb. Fair? If the neighbor's kid runs out into the street, I on my bike swerve and avoid him. The guy in the pick-up truck smears him into road kill. What would be "fair" would be that bicyclists and drivers were each held to a high standard of risk they present to their fellow beings. It makes as much sense to conclude cyclists need follow the same rules as drivers as it does to conclude the same standards should be applied to a water pistol as to a 45-caliber handgun.

Anyway, I really hope this thing passes in Oregon. California is California: it like to talk the talk but the reality is in progressive social issues, especially those threatening the supremacy of the car, it often lags behind. But with the more other states move ahead on rationally treating cycling as a specific transportation mode, the more California will be prompted to follow.