In the privacy of your car? April 5, 2013
Posted by Cameron Shelley in : STV302 , comments closedThe term “black box” can refer to a recording device, often associated with planes or trains, that records operational data during usage. The black box was in the news not long ago in connection with the fate of Air France flight 447 that crashed in the mid-Atlantic in 2009. The black box contained data from the instruments and control systems of the plane that helped investigators to reconstruct the accident, with a view to preventing similar disasters in future.
What is less well known is that cars often contain black boxes as well, where they are known as Event Data Recorders (EDRs). Like black boxes in airplanes, EDRs were designed to record instrument and control data with a view to safety, that is, the reconstruction of accidents for purposes of preventing future problems. The nature of an EDR depends on the make of the car and local regulations, but a typical list of data captured would include:
- speed;
- engine rpms;
- applications of the brakes;
- applications of the accelerator.
Naturally, such data is useful not only for safety but for legal purposes, for example, determination of fault in an accident. So, who owns the data, and who can gain access to it? For what purpose?
The issue is not new but has received renewed interest because the US National Highway Traffic Safety Administration has proposed making the devices mandatory on all cars, starting next year.
The Electronic Frontier Foundation has proposed that people should be able to opt out of having the data recorded, and that police should require a warrant before having access to any data available.
If US law is unclear on the subject, it appears that Canadian law is no further ahead. Here is an excerpt from a recent article on the topic:
There is no legislation in Canada specifically governing the admission into evidence of EDR data. The federal and provincial Evidence Acts should be amended to permit the admission of the evidence either as a “business record” or on a basis similar to blood-alcohol test devices.
I am not sure what that means, but it sounds interesting.
What sort of privacy protections, if any, are appropriate for EDRs?
(Pava/Wikimedia commons)
Cars and cities January 23, 2013
Posted by Cameron Shelley in : STV 201 , comments closedAs is well known, cars have had a huge impact on cities. Many cities have been drastically reshaped in order to make car travel more efficient and convenient.
A reminder of this observation comes from this posting in The Atlantic Cities blog. The posting describes a project called “Postcards then and now“, which compares views in English cities (and countrysides) from historic postcards with similar views of the same locations as provided by Google Streetview. The change in civic landscapes on display can be quite instructive.
My attention was caught by this image of a roadway in Aston, a city in the English Midlands. The postcard image shows a major intersection, ca. 1910, called “Six Ways”, presumably for the number of roads it joins. (It reminds me a bit of a junction called “Five Corners” near by own home in Guelph, Ontario.) The postcard shows a thriving junction featuring a post office, a chemists (pharmacy), and a bank (the one with the clock over the doorway). The Google Streetview image shows “a dreary roundabout”. I wonder how many of drivers in the Streetview image are on their way to some distant pharmacy or drive-thru ATM.
(Howard/Postcards then and now)
The alteration of the streetscape is nearly total!
What would you find out from similar comparisons in your own city?
The Red Car conspiracy January 15, 2013
Posted by Cameron Shelley in : STV 201 , comments closedThe 99% Invisible podcast has a great synopsis of the supposed Red Car conspiracy of Los Angeles. The basic story is that LA once had a thriving street car service known as the Red Car. However, the Red Car service was bought up by car companies such as General Motors, who tore it down in order to replace it with the current freeway system thus forcing Angelinos to use cars in place of public transit.
This conspiracy theory has been embedded in popular culture, notably in the plot of the movie Who framed Roger Rabbit. In the movie, the character Judge Doom confesses to his plot to subvert the position of the transit service:
Eddie Valiant: Nobody’s gonna drive this lousy freeway when they can take the Red Car for a nickel.
Judge Doom: Oh, they’ll drive. They’ll have to. You see, I bought the Red Car so I could dismantle it.
As Eric Molinsky points out in the podcast, the true story is quite different. The LA streetcar service was used as a loss leader by land speculators, especially Henry Huntington, to drive real estate sales. Basically, they built streetcar routes out into the countryside where their new suburbs were being developed. The streetcar service increased property values by allowing prospective home owners to commute to their jobs. The streetcar lines were never meant to be viable in their own right.
When the automobile did arrive on the scene, the streetcar service, which always operated at a loss, could not compete. Many streetcar routes were destroyed and some were eventually replaced by the city’s now infamous freeways.
It is true that car manufacturers like GM sought to replace streetcar services, but accusations of conspiracy were never proven. Nevertheless, the efforts of GM and others to replace streetcars with buses fueled suspicions and supported the conspiracy theory. It seems clear, however, that the demise of early streetcar services in Los Angeles was due to the fact that the services were never designed to succeed in the first place.
In the video below, you can follow along on the final ride of the LA Red Car.
Have we reached “peak car”? September 27, 2012
Posted by Cameron Shelley in : STV202 , comments closedThe Economist has an interesting article concerning the notion of ‘peak car’. The idea is based on the notion of peak oil, the point in time when oil production reaches its maximum and then begins to fall off. Similarly, the notion of peak car is the point in time when the number of cars reaches its maximum and starts to decline.
(Bull-Doser/Wikipedia commons)
The issue arises because, by some measures, car usage seems to be hitting a plateau or is even falling off, depending on where you look and what you look at. For example, it seems that car ownership and vehicle-kilometers travelled per car have leveled off in the US and even declined in Europe and Japan. There may be a number of reasons why this is happening. Economic recession may be preventing people from traveling by car as much as they would like. It could also be that our infrastructure has become saturated with cars, such that making more trips or longer ones is simply not worth the aggravation. And it could be that alternative modes of transport are competing successfully with cars for ridership.
One issue connected with this trend remains unclear: Is it cars that people are increasingly leaving behind, or is it the task of driving them that is losing its lustre? On the first issue, it could be that cars no longer occupy their prominent position in the material culture of the developed world. The increasing popularity of car-sharing services, such as Zipcar, suggests that some drivers, mainly younger ones, see car ownership negatively:
Fleura Bardhi of Northeastern University in Boston interviewed users of car-sharing schemes, much more popular among the young than their elders, and likened the youngsters’ attitudes to cars to their attitude to dating: “People get to try out different cars, different lifestyles, different identities.” By contrast owning a car, they said, felt like being tied down—like a marriage.
Take that, old married people!
On the second issue, it may be that many people still want to own a car but find the task of driving one to be disagreeable. The article notes that the saturation of roadways with cars has meant that commuting times have grown past the point that many people will accept.
In 1994 the physicist Cesare Marchetti argued that people budget an average travel time of around one hour getting to work; they are unwilling to spend more.
When commute times exceed this limit, people seem to prefer to move back into cities from the suburbs. There, they then take public transit or other means of transport to their jobs.
Car producers are apparently hoping that the second explanation is correct. This is perhaps one of the factors driving the development of self-driving cars. As automotive scholar Tom Vanderbilt has noted (see this blog entry), time spent in the car commuting is seen as unproductive by many commuters. Thus the temptation to read emails and fire off texts while driving, in order to utilize this “lost time” productively. A car that drives itself frees up the occupants to work while they move. Also, self-driving cars may be able to utilize the roadway more efficiently, packing themselves in to “road trains” and the like. So, it is hoped, people who might abandon their cars because driving takes up too much of their time might be tempted to purchase self-driving cars that take over the unproductive task of driving for them.
So, what looks more attractive to you? A self-driving car, a car that you borrow from a car-share service, or no car at all?
The future of the dumb car September 20, 2012
Posted by Cameron Shelley in : STV100, STV202 , comments closedThe IEEE predicts that, by 2040, people will no longer require drivers’ licenses. This is because their self-driving cars will be doing all the driving.
(Mariodo/Wikimedia commons)
It would be easy to conclude, then, that the old-fashioned car with no autopilot will become obsolete and disappear. However, as we have noted before, obsolete technologies sometimes live on in new forms, perhaps as specialized goods or in specialized niches. Something like this could happen to the “dumb car”. In fact, the good old dumb car may find at least a couple of niches in the world of 2040.
One future I can imagine for non-smart cars is as a vehicle for off-beat recreation. In 2040, you may be able to spend the day at a Car Ranch, learning the old-fashioned art of driving a car. Think of horse transportation. Once, the horse was the workhorse of transportation, pulling riders and wagons along the dirt roads of the sepia-toned past. After the uptake of the car and the paved road, the usefulness of horses for everyday transportation waned. Nowadays, horse riding is done in special facilities, such as ranches and designated horse trails. Riders learn to handle the reins via special instruction.
In future, something similar may be the case with drivable cars. To experience the atavistic thrill of actually driving a car, customers will be taken by their robocars to special camps where they can ride in automobiles that are too stupid to drive themselves. Customers can learn what it was like to stop at a “stop sign”, flip on a turn indicator, and learn what a “blind spot” is on a car.
It is also possible that driving dumb cars may become a recreation for an elite group. In his book The theory of the leisure class, Thorstein Veblen pointed out that social elites sometimes affirm their high status through economically unproductive activities. While the working classes toil away in factories, the well-to-do indulge in cricket matches that last for days, or in spending the day betting on the ponies at a race track. In some cases, these leisure activities were survivals of previously productive ones, such as hunting or archery. In the Middle Ages, hunting and archery were survival skills for most of the population. However, in the industrial era, taking the time for a fox hunt or an archery tournament was a display of conspicuous leisure.
Perhaps a similar fate awaits the dumb car. The majority of the public will adopt the smart car and will spend the time freed up from having to pay attention to the road by paying attention to their iPhones or in-car entertainment systems. A well-to-do minority might, however, decide that actually driving a fancy car around would be a fun way to spend the afternoon, and to show off how well-to-do they actually are. Of course, the cars driven for this recreation will not be mere “dumb cars”. Instead, they will be curvaceous red sports-mobiles, or silver-colored luxury sedans.
In the year 2040, then, we may find dumb cars on the road confined not so much to the least wealthy drivers but to the most wealthy ones. As our roadways get redesigned for smart cars, it may be that the most significant resistance comes from the social elite, who desire to show off their rare rides and their leisure status on the public streets and highways. They may demand that the road system remain backwards compatible with user-driven cars. And, for rest of us, there is always Randy’s Retro Car Ranch.
Phone squatting June 7, 2012
Posted by Cameron Shelley in : STV202 , comments closedAn article about a new phenomenon, that I will call “phone squatting”, appeared in a recent New York Times. In a nutshell, phone squatting means parking your car in a parking space and then using your phone for calls, texts, etc. This phenomenon seems to be on the rise, and is sometimes a sore point for other drivers who covet the spot occupied by the squatter:
Brianne Miller was parked recently in downtown San Francisco e-mailing on her BlackBerry. She heard a honk, looked up and discovered a man in a BMW waiting for her spot. She signaled to him that she would be a few more minutes.
“He flashed an obscene gesture,” she said. She smiled and waved, trying not to escalate things. “He sped off in a huff,” she added with a laugh. “It was a really, really good spot.”
The article notes that the increase in phone squatting would seem to be a positive thing: It may reflect the growing acceptance that driving while texting or talking is not a good idea. Better to pull into a parking spot to use the phone.
The article, I think, does not get to the bottom of the drawbacks of phone squatting. As the example above suggests, the immediate issue is that other drivers may desire the spot taken up by the squatter. The person wanting the spot then gets frustrated when it becomes clear that the spot that seemed to be opening up is, in fact, not available.
If that were the only issue, then I think that phone squatting would not merit much attention. We would simply get used to this new and understandable practice. However, phone squatting also undermines the social contract that underlies how drivers share parking spaces. The understanding is that the purpose of parking spaces (in most cases) is to provide drivers with access to neighboring amenities, such as stores. That is, a driver parking in a spot is expected to get out of the car, do some shopping or visiting, and then return and leave, freeing the space for another visitor. The practice of phone squatting violates this expectation because it treats the spot itself as the amenity: The driver does not exit the car while making use of the spot. Other drivers may see this use of parking spaces as illegitimate. As Brianne Miller notes, she had a “good spot”, good not merely as a place to put a car but good as a place from which nearby amenities could easily be accessed.
What is to be done? One option is to do nothing. With time, the public may simply come to understand in a new way how parking spots are to be shared. If drivers come to regard them as amenities in their own right, then the problem will cease to exist, at least as a matter of social contract. However, many parking lots are provided by businesses for the convenience of clients, and those businesses are not likely to welcome squatters. Perhaps certain spaces could be designated for squatting, much like spaces for people with special needs. Spaces on the periphery of parking lots might be ideal, as they would be less likely to inconvenience paying customers. Of course, businesses may not be thrilled with paying for such spaces either, although it might make for some good PR.
Another possibility would be for government to pay for parking spaces designated for squatting or, at least, available for squatters. Given the increase in public safety to be had from providing such spaces, this system might be a good value for the public expenditure. Of course, taxpayers might insist that drivers should simply upgrade to hands-free devices, which remain legal for use while driving in many jurisdictions. Why make the public subsidize drivers who do not invest in proper equipment?
In fact, I think that designing a proper solution to this issue would have to await more systematic study of it. Where does this issue really become a problem, when, and for whom? Whatever the answer, it provides a good illustration of how the design of technology, including cell phones and parking, reflects a mutual understanding about how certain resources are shared in the public realm.
Is your car too smart? May 18, 2012
Posted by Cameron Shelley in : STV202 , comments closedRobert Charette at IEEE Spectrum reports on complaints that computerized amenities in modern cars are too confusing for many drivers. Car producers are packing more and more computerized features into the cabins of cars for operators to interact with. Unfortunately, the operators sometimes have difficulty figuring out how to work their new toys. The MyFord Touch system, for example, has attracted complaints that it is too complex for people to operate.
(Aaaaplay/Wikimedia commons)
To deal with the problem, Ford is trying to persuade dealers to become more expert in the operations of these new, in-car electronics. With greater training, dealers can then help to train buyers in the ins and outs of their new computerized gear.
Charette puts the problem down to poor design:
Of course, it might help if car designers spent a little more time with their human factors counterparts to make the operations of the electronics more transparent and easy to use. There has been several occasions where I would have been more than pleased to explain in detail to the designers of several of the electronic systems on my Toyota Sienna how they got it dreadfully wrong. Needing a couple of hundred page manual to explain how to use my car’s electronics is a symptom of the problem.
It would not be the first time that poor design sabotaged a new, in-car system. Early versions of BMW’s iDrive system were notoriously difficult to deal with, requiring drivers to use a joystick to navigate a hierarchical menu system to operate the simplest functions, e.g,. the radio, all while driving at speed. Usability has always been an issue for the software industry, which has a tendency to present functions in a way that prioritizes their abstract relationships rather than their practical uses. Now that cars are ever more computerized, these problems with software design have become problems for automotive design.
The response of having dealers train users is reminiscent of the problem of training new drivers when cars themselves were a new invention. In his book, “User unfriendly“, Joseph Corn documents how the first automobiles confounded their users. Cars were radically different than the familiar horse and buggy, and early operators experienced many problems with driving and just keeping their machines working. Auto manufacturers responded by training dealers enough to talk up the features of their cars, and by issuing manuals that purported to explain their purchases to new car owners. Neither effort was much of a success. The situation was amended only when new technologies made cars reliable enough to work without so much fuss by the drivers.
It may be that this will have to happen with in-car electronics too. That is, instead of training drivers to adapt to their gear, automakers will have to design the gear so that drivers can operate it without so much preparation.
Stop worrying and love your robot car February 10, 2012
Posted by Cameron Shelley in : STV202 , comments closedTom Vanderbilt, author of Traffic: Why we drive the way we do, has posted a piece on Wired responding to critics of autonomous or robot cars. Vanderbilt does not name the critics whom he rebuts, so it is difficult to tell if he represents them correctly and fairly. However, the points he makes seem sensible enough on their own merits.
(Alex Goy/Wikimedia Commons)
Two points, however, may present difficulties that do not receive adequate attention in his brief commentary. Let’s start with autonomy and privacy.
Vanderbilt notes that some people may object to robot cars because they would allow Big Brother, aka the government, to have a larger say in the behavior of your car. The point is, I gather, that some drivers enjoy illegal practices such as speeding, or drinking, texting, or watching TV while driving, and so on. A robot car would be programmed to obey all local rules and regulations, and would also be programmed to rat out occupants who break them. Of course, it might be worth pointing out that drinking, watching TV etc., might not be considered an offense in a robot car.
In defense of Vanderbilt’s anonymous critics, robot cars will raise issues with driving and traffic that simply do not exist with human drivers. The problem of managing accidents is one that has already been considered in this blog. Another would be the potential for increasing complexity of traffic regulation. Consider speed limits. Presently, speed limits tend to be fairly generic, with major highways having a default limit of 110 km/h (here in Ontario), county highways 80 or 90 km/h, and city streets 50 km/h. One could imagine matching speed limits much more precisely to local conditions. A single stretch of road could have dozens of speed limits at different points, depending on how straight they are, how narrow, how far from housing or schools, and so on. And then there are weather conditions to think about. The possibilities for regulation of autonomous cars may be nearly boundless. The introduction of autonomous cars will raise many new issues for governments and citizens to consider. My point is not that we should ban robot cars. It is just that a robot car is more than just a tool; it cannot be added to the existing traffic system without affecting that system in return. A similar story will apply to considerations of privacy.
Another point that Vanderbilt raises is whether or not autonomous cars will increase or decrease the amount of driving that occurs. Vanderbilt is skeptical that Jevons’ Paradox will apply. This is the argument that, since robot cars will likely be more fuel efficient that regular cars, that people will consume their savings by making more trips and at longer distances. As he implies, there is only so much time in the day, and people have other things they would likely prefer to do than sit in a car. So, this factor should limit any effect from the Paradox. However, as Vanderbilt concedes, the situation is not so simple. With the car driving itself, the driver’s attention is freed up for other tasks, such as sending and reading emails:
The utility of the commute could theoretically improve as people once stuck driving the car can now fire off e-mails with abandon. Then again, this increased utility might lead to more people taking advantage of the utility, thus leading to more traffic and more time spent in gridlock. At which point you might long for that other, essentially “self-driving” vehicle: the train.
In other words, the autonomous car will probably increase the productivity of each car trip for its occupants. Thus, the effective cost of the trip will decrease. It will be as if, along the lines of Jevons’ argument, you had added more time to the length of the day. In that case, people might well be willing to consume that “extra” time, while their car drives them places. In that event, fuel consumption could actually rise as a result of the introduction of robot cars.
As Vanderbilt says, neither of these observations provides a compelling reason to ban or abandon autonomous cars. However, neither should we think of the introduction of such cars as being just like the introduction of a new model year in an existing type.
Stay in your lane! January 24, 2012
Posted by Cameron Shelley in : STV202, STV302 , comments closedThe New York Times has an article discussing computerized systems that allow cars to stay in their lanes by themselves. Basically, forward-facing cameras on the rear-view mirrors attempt to track the painted lines on the road and keep the car in between them. If the car begins to drift out of the lane, then the system can display a message, issue a verbal warning, or even instruct the steering system to bring the car back within its lane. The system can be disabled by the driver and remains inactive if the car’s turn signal is on.
(Don O’Brien/Wikimedia Commons)
The basic idea is definitely a win. After all, when a car leaves its lane unintentionally, then the risk of an accident increases. The article also notes some of the limitations of this kind of system. For example, marks on the roadway may not be very distinct and thus would be impossible to follow. Also, glare from the sun or from the headlights of oncoming cars can wash out the image in the cameras, rendering the system unusable. I presume that the system is programmed not to take any action when it detects such circumstances.
Another issue pointed out in the article is that of risk compensation, the tendency of people to increase their acceptable level of risk due to their knowledge that safety equipment is present. If drivers believe that their cars will automatically keep them in their lanes, then they may cease to pay close attention to the road, raising the risk of an accident due to some unnoticed problem. The likelihood of such behavior increases further given that most drivers will have other gear, e.g., cell phones, that soak up any spare attention.
I would just add that there is the potential for privacy and security issues as well. The article does not say, but I imagine that the system tracks the history of its use in an on-board computer. Thus, someone could access the car’s computer and figure out whether or not it left its lane. It might be possible to correlate this information with any GPS or other data available in order to reconstruct a complete log of the car’s whereabouts and behavior. Who should be allowed access to this data? Of course, the police could obtain it with a court order. But does it belong to the car’s owner or the manufacturer? Car manufacturers might find uses for the data, perhaps to mine it to analyze how their cars are actually driven on the roads, and how they perform under different conditions. Nissan supplies similar data from its cars to a social network called Car Wings that it runs. This network tells drivers how they have been doing, compared to their past history and to other drivers. These comparisons are intended to help drivers use their cars more efficiently. Will data from lane-keeping system end up on a proprietary network? Will manufacturers strike a deal with Facebook to post the data there?
Of course, insurers would be interested in the data as well. I would guess that drivers who let their cars wander out of their lanes more frequently would be charged higher coverage rates. Perhaps that is a good idea. Currently, the Ford privacy policy covers information contained in the car’s Event Data Recorder, which keeps data from only the previous 30 seconds. Of course, that restriction would not apply to data kept for posting on a social network.
Then there is the security issue. The computer systems in cars are vulnerable to hacking, even from outside the car itself. Security researchers have been able to hack into cars and control the vehicle brakes, one wheel at a time, for example. A car with an autonomous lane-keeping system might allow a malicious intruder the opportunity to take over the steering system as well. It is important for the acceptance of more automated automobiles that they do not become more vulnerable to outside interference.
The “check engine light” considered harmful January 18, 2012
Posted by Cameron Shelley in : STV202 , comments closedA recent Wired.com article discusses why the check engine light on modern cars is, at least, lame. As most readers already know, the check engine light is a little glyph somewhere on your dashboard that lights up whenever your car’s onboard computer detects some sort of engine fault. As Jason Torchinsky argues, to have a generic light that comes on when something goes wrong is rather uninformative. In this respect, it is like getting an “invalid input” error message after entering text into a field in a computer app or Web site. Since you do not know what the nature of the error is, the message is merely frustrating.
(Wikiuser100000/Wikimedia Commons)
Of course, as Torchinsky admits, the driver could buy a special scanner to plug in to the car’s diagnostic system in order to read the error code and find out what the problem is. However, as he points out, not many drivers are likely to want to keep such a scanner around, or even feel confident about using it correctly.
In a way, the “check engine” light is worse than the “invalid input” message. In the case of the input message, the frustration comes partly from not being told how to correct the problem. The “check engine” light does, however, suggest a course of action: Take the car to the dealer. Torchinsky objects that this setup puts car owners at the mercy of mechanics:
By failing to provide this information to consumers, regular drivers — that is to say, those who aren’t going to ferret out the codes themselves, and then fix the problem — are beholden to dealerships and mechanics for information readily available in a product they’ve paid for.
The commercial purpose of the “check engine” light is, then, to create anxiety in drivers that can be relieved only by purchasing information from a professional.
Torchinsky points out that there are alternatives. Many cars today incorporate video screens into the dashboard. It would seem to be a simple matter for the designers to use those screens to display the diagnostic message that would otherwise appear on the special scanner.
Torchinsky’s complaint reminds me of a similar issue raised by Matthew Crawford. In his book Shop class as soulcraft, Crawford argued that automotive designers, in particular, cultivate a sense of learned helplessness in their customers. A new model motor bike, he points out, has a light that comes on when the engine oil needs to be topped up. The light is supposed to prompt the owner to take the bike to a dealer for remediation. Replenishing engine oil should be a snap for any bike owner, Crawford scoffs, so this design feature is merely a craven ploy to substitute a kind of passive consumerism for basic mechanical savvy among owners, to the benefit of dealers.
I suppose that one could argue that a “check engine” light, like a “change oil” light, is consistent with the tenants of user-friendly design that is much promoted today. The lights impose as little as possible on the car or bike owner, while directing them to take some appropriate action when a problem occurs. Crawford’s response is that designs should sometimes impose on their users; it is an opportunity to teach the user how their gear works. To miss this opportunity is to deprive the user of the dignity that comes with command of their gear.
Torchinsky’s objection falls into the consumer protection category. The “check engine” light simply places the car owner at a disadvantage:
Information is power, and by denying you this information, automakers are denying you power. If you’re driving along and that damned check engine light comes on, you have no way of knowing if it’s a minor problem — the gas cap is loose, for example — or you’re at risk of imminent engine failure. A generic check engine light also makes it easier for dishonest mechanics to take advantage of unknowing customers.
Maybe. Of course, most owners will not need assistance fixing a loose gas cap. However, many owners may simply be confused by a detailed error message such as “Secondary air injector: incorrect flow”, which is displayed in the picture in Torchinsky’s article. As cars get more complex and computerized, they will only become harder for most owners to understand.
So, I suspect that the situation needs more thought. Torchinsky is right that the “check engine” light is an inadequate design for today’s car. However, most drivers will derive little benefit from a technical description of some engine fault appearing on their dashboard. Instead, designers need to think about a model of the car’s systems, an idealization of some sort, that owners can understand and that will help them to take appropriate action when a problem occurs. In that way, owners can be educated as far as is possible, and saved from the machinations of their mechanics.
