Slashdot Mirror


IBM's Patent-Pending Traffic Lights Stop Car Engines

theodp writes "I'm sorry Dave, I'm afraid I can't let your engine idle. The USPTO has just published IBM's patent application for a 'System and Method for Controlling Vehicle Engine Running State at Busy Intersections for Increased Fuel Consumption Efficiency.' Here's how Big Blue explains the invention: 'The present disclosure is directed to a method for managing engines in response to a traffic signal. The method may comprise establishing communications with participating vehicles; responding to a stop status indicated by the traffic signal, further comprising: receiving a position data from each participating vehicles; determining a queue of participating vehicles stopped at the traffic signal; determining a remaining duration of the stop status; sending a stop-engine notification to the list of participating vehicles stopped at the traffic signal when the remaining duration is greater than a threshold of time; responding to a proceed status indicated by the traffic signal, further comprising: sending a start-engine notification to a first vehicle in the queue; calculating an optimal time for an engine of a second vehicle in the queue to start; and sending the start-engine notification to the second vehicle at the optimal time.' IBM notes that 'traffic signals may include, but are not limited to, traffic lights at intersections, railway crossing signals, or other devices for indicating correct moments to stop and to proceed.'"

32 of 423 comments (clear)

  1. Railway crossing? by Anonymous Coward · · Score: 5, Insightful

    Hmmm, a computer at a railway crossing that can remotely disable a car's engine. To use the parlance of our times "What could possibly go wrong?"

    1. Re:Railway crossing? by amiga3D · · Score: 3, Insightful

      Actually engineers should be asking this question in all products and systems. That helps prevent things going wrong.

    2. Re:Railway crossing? by Anonymous Coward · · Score: 5, Insightful

      Of course they go after controlling your engine instead of fixing the problem of the lights not being synchronized and optimized to begin with.

      It's 2010 there is no excuse to drive into every city in the U.S. to stop and sit at every light forever while there are no cars coming from the other direction.

      We should all charge the Government for our wasted time and fuel.

    3. Re:Railway crossing? by Anonymous Coward · · Score: 3, Insightful

      Actually, engineers DO ask that. It's the business side that don't, or just don't care.

    4. Re:Railway crossing? by PopeRatzo · · Score: 4, Funny

      So, when you try to beat a yellow, you lose power steering and brakes?

      I vote for ejection seats.

      --
      You are welcome on my lawn.
    5. Re:Railway crossing? by Maxo-Texas · · Score: 4, Insightful

      Also, what about ambulances, police, pregnant ladies being rushed to the hospital.

      And what about that STUCK red light at 3am in the morning. (motorists drive in, but they don't drive out).

      --
      She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
    6. Re:Railway crossing? by RobertM1968 · · Score: 5, Informative

      Hmmm, a computer at a railway crossing that can remotely disable a car's engine. To use the parlance of our times "What could possibly go wrong?"

      Besides the possibilities of "what could possibly go wrong?" the simple fact is, I am hoping IBM has done their research on this.

      Some car manufacturers claim that stopping and restarting the engine will use more gas, and cause increased wear on the starter. Others claim it will save as much as 10% in gas and not cause wear on the starter. I wonder where the truth really lies? Jeep recommends (for some of their vehicles) at least 1 minute of idle time expected before one turns off the engine to save gas. The government says (basically) "do it every time" - but the government also says that modern cars only need 20 seconds to warm up to a usable temperature in the winter. For those of you who have an actual temperature gauge in your car, you know that is not true... so I am not sure how accurate the rest of the government's data/speculation is (or quite simply, they did not test enough cars).

      That aside, there are other problems I have not seen mentioned, for instance dead batteries. If you are a city driver, and barely get over engine idle rpm during your drive, constantly stopping and restarting your engine can drain your battery. There are times I've had to drive in NYC and been on a two way main street going against the flow of traffic lights, meaning I've gotten stuck at a bunch of traffic lights during my trip. As anyone who has had engine (or lack of fuel) problems has noticed, if one repeatedly tries to start their engine, the battery will eventually get below "restart power levels" - meaning a bunch of people stuck at a traffic light without enough power to restart their engine. Add a cold winter day into the mix and this definitely should apply. As it is, I have experienced "uber cold" days on my visits to upstate New York where it sounded like if I had two or three attempts to start my engine, I would be lucky. Fortunately, my car only requires one. But driving a few hundred feet, shutting it off and trying again, then repeating that 5-10 times in under a mile would probably run me into problems as the car wouldnt have been running long enough at high enough RPM (1800?) to (a) recharge the battery enough for another start at those temperatures and/or (b) heat the battery enough for it to be able to deliver more starts.

      Also, unless starter technology has changed recently, the starter has a cool-down period between start attempts. Something mentioned in only a few car manuals simply because one starts the car, drives it, then shuts it off - usually exceeding the cooldown period. If you are needing to stop at a traffic light every city block, and restart your engine, then chances are, you aren't reaching the end of the cooldown cycle. The more the starter is turned on without reaching it, the hotter it gets. Anyone who has played with an electric motor knows what happens if they overheat.

      And as for the engine wear part of the equation, as anyone who knows a little physics can tell you, starting an engine does wear it more than normal driving... something to do with overcoming inertia (ie: the massive flywheel, and the internal inertia of the engine itself). Yes, above-normal driving (and to a much lesser extent, normal driving) still has similar factors to overcome, but there are other differences involved, namely that the flywheel is before the torque converter or clutch and the torque converter/clutch "absorbs" some of the "stand-still" force being overcome in driving/accelerating (ie: not as jarring to the engine - in comparison to "wrenching" a standing still flywheel into motion).

      And of course, all of the above could entirely be speculation... but that's not really the point that matters... the point that matters is, it's all based off one or more combinations of vehicle manufacturer information, various studies on the matter, and various real world applications of the situation (cold s

    7. Re:Railway crossing? by Metabolife · · Score: 3, Interesting

      Meh, I'm still waiting for the traffic light that controls all the cars by using an LED and manages the cars to all go near full speed through the intersection without collision

    8. Re:Railway crossing? by HeronBlademaster · · Score: 4, Informative

      On top of that, some cars already do what IBM wants, albeit without actually checking if you're at a stop light, and without potentially giving control of your engine to a remote computer.

      My Civic Hybrid will shut off the engine if you're stopped on level-ish ground for more than a few seconds, as long as you're holding the brakes - as soon as you let go of the brakes, the engine kicks back on. It seems to me that this is a cheaper and more general solution to the problem IBM is trying to solve, since IBM's solution doesn't save any gas if you're sitting at a regular old stop sign for ten minutes waiting for traffic to clear up.

    9. Re:Railway crossing? by ehrichweiss · · Score: 3, Funny

      Think of all the fun you could have with the people who are talking on a cell phone, smoking a cigarette and reading the newspaper while driving..

      --
      0x09F911029D74E35BD84156C5635688C0
    10. Re:Railway crossing? by Mr.+Freeman · · Score: 3, Insightful

      Not to mention that the ignition cycle is the most demanding thing on a car's engine. This system would wear out your engine one hell of a lot faster. I expect all automakers to be in favor of implementing this system because you'll have to buy a new car every few years.

      This is just another reason I'm extremely wary of buying a car with lots of computer controlled components. OnStar has allowed the government to track you, OnStar can shut off your engine if the feel like it. There was a case where some dealer's system was "hacked" by a disgruntled employee and he remote killed hundreds of card. Toyota's software causes uncontrolled acceleration during which the transmission will apparently not allow you to shift into neutral. Their response? Blame cosmic rays and sue people rather than admit fault and fix it.

      I love my '98 subaru. Not a whole lot that can go wrong in a car with only minimal computer control. The brakes are mechanical work, the throttle is mechanical, the transmission is mechanical in terms of drive/neutral/park. The computer probably controls valve timings and stuff, but nothing to remote start/stop the car and nothing that's going to send me flying into a brick wall at top speed.

      --
      -1 disagree is not a modifier for a reason. -1 troll, flaimbait, redundant, overrated are NOT acceptable substitutes.
    11. Re:Railway crossing? by anegg · · Score: 4, Insightful

      Gee, an interface in the engine of every single car on the road that can be remotely controlled at an incredibly large number of geographical locations. I'm sure there won't be any security problems, because IT has such a good track record in security.

      Demonstrate that a technology *can* be done right first, before calling those who are justifiably cynical of success "Luddites"

    12. Re:Railway crossing? by Anonymous Coward · · Score: 4, Informative

      Your explanation doesn't fully communicate the ingenuity of the automatic engine stop/start system. If the engine just stopped, the additional load on the alternator to recharge the battery after starting could conceivably negate any benefit from the short stops that it would mostly be used for.

      Modern stop/start systems actually use the ECU to halt the engine in a configuration where one or more of the cylinders have a primed and compressed fuel/air mix sitting right there ready to be ignited. All the engine needs to do to start again is give those cylinders spark. No starter motor needed, no energy wasted, and the engine starts almost instantly. It's incredibly smart, one of the few environmental car things which is an improvement in every objectively measurable way. There's no reason not to have it on any car, and that's a rare thing.

      This patent is retarded.

  2. Yes, novel, non-obvious and useful... by russotto · · Score: 4, Interesting

    ...if you don't ignore the fact that this is a blatant case of "patenting the goal". The patent is "here's a bunch of ideas that might work to control fuel consumption at signals, we claim them all."

    1. Re:Yes, novel, non-obvious and useful... by Cassini2 · · Score: 5, Insightful

      I've never perceived the problem of getting vehicles to turn off engines at traffic lights as being a technical issue. Rather, the problem is much more one of regulation, and forcing everyone to adopt a standard. To make the strategy work, you need to:

      (a) get every state in the union, and perhaps every municipality in every state, to modify their traffic lights in the same way, and
      (b) get every automaker to make cars that with electronic modules that work with the *SAME* standard as the traffic lights, and
      (c) get every class action litigator to agree to not sue anyone.

      Business text books clearly say to "run away" from any system that requires broad corporate/public/governmental agreement, particularly if the system involves long-term governmental and corporate cooperation.

    2. Re:Yes, novel, non-obvious and useful... by cynyr · · Score: 3, Informative

      to add a few points to your list

      There are a lot of collector/hobby cars on the road, from the 40's-80's. My car is from 1994, i'm sure that it does not have the necessary bits in it to make this system work, nor am I likely to pay out of pocket for it. If you could even get to 90% of cars on the road, in less than 50 years I would be shocked. Thats assuming that A, B, and C all went off without a hitch.

      A few problems with turning the engine off at a stoplight (brought to you by the "whatcouldgowrong dept.):

      • Emergency vehicles may need to pass though the intersection. How do you start all of the cars back up? Does the heater/AC units still work without the engine running? I guess we could move to having only the alternator attached via belt, but that still would mean powering a compressor/heater from the battery. Not something i would want to do at a very long light. Power steering would also be "disabled" with the engine off, as well as vacuum assist on the breaks. A large number of critical systems in a car work because of the engine
      • Does anyone have this "auto power down" stuff for manual transmissions? If so i'm not sure i would like that the car can override my clutch pedal. It could cause problems if i'm relying on the stopped engine and transmission to keep my car in place. That is very very common to do for parking a stick.
      • Restarting an engine uses more gass than constant running for X seconds, if the system just stops until Y seconds before the green light, you could actully increase gas consumption, if it was sending out a "light green in 45 seconds, manage your engine please" sort of a signal, that would allow for "a red && yellow" sort of light so you could get a good launch off of the traffic light, or just jump the green. The US anyways seems to dislike the idea of letting people know about the green light ahead of time.
      • Cars where the battery is dead and need to be left running to get to the garage could wind up stopped with no power in the lane of traffic just before an intersection. Where if the light had not instructed them to turn off it would have been fine. To illustrate, I can ruun my 1994 car without a battery. The starter won't work, but if it gets jumped or I push start it runs just fine, but is a stick though.
      • The signal would have to be a real data stream with a one time key, anything else would be record-able and would be able to be played back at will to stop a car by anyone with ham radio gear.

      just a few things off the top of my head, that could be technical problems with the idea.

      --
      All of the above was encrypted with a Quad ROT-13 method. Unauthorized decryption is in violation of the DMCA.
  3. Sounds good. by 0100010001010011 · · Score: 4, Interesting

    VW (and other car manufacturers probably) already have cars that shut off at stop lights. The "3L" car they made (78.4 MPG, no batteries required) shuts down at stop lights. All this is doing is making it 'intelligent'.

    1. Re:Sounds good. by TerranFury · · Score: 5, Insightful

      The problem is the damn headline, that makes the idea sound Orwellian. It isn't. It's not about disabling your engine, or some other DRM-style idea. It's about giving your car additional information that it can choose to use to increase fuel efficiency.

      Are you familiar with the idea of correlated equilibrium from game theory? By giving players a common instruction, which they can choose either to follow or to disobey, you can often get better Nash equilibria than if you simply made the players decide what to do independently. That's what this is -- applied to engine management.

    2. Re:Sounds good. by Teancum · · Score: 4, Insightful

      Some of this is an issue of reliability and having an engine designed for multiple restarts. For at least older gasoline vehicles, starting an engine can cause hell on the internal wear of engine parts and is generally discouraged on a practical dollars and cents level as you will be paying far more in engine repair bills than the little bit of money that you save for turning off an engine. Even if you are a backyard mechanic and figuring in the cost of the replacement parts alone, it can get quite expensive. If you factor in the environmental factors for metal refinement used to make these parts and shipping those parts across the country to get them to you, it could be argued that turning off engines actually does more harm to the environment and perhaps even more carbon pollution than simply keeping the engine running.... at least if the time you keep the engine off is but a short period of time. The rule of thumb I've heard is you start to save money if you are going to be stopped for more than a few minutes... that is not the amount of time people are typically at an intersection waiting for a street light.

      The point being that you need a vehicle designed explicitly for being turned off and restarted on a whim and have that happen repeatedly during a typical driving experience.

      BTW, part of the patent here is that it specifically addresses the above issue I mention, where the manufacturer puts into is electronic control system some sort of calculation for how long an engine ought to be kept on before wear and tear on the engine from restart begins to do some damage, and if the traffic signals "intelligently" indicate that the wait time is going to be longer than that predetermined time period, that the engine shuts off while the car is already stopped anyway. It is an interesting solution to the issue, but I'm not really sure how "non-obvious" that concept really is if the goal is to engage in saving fuel in this manner. A competent automotive engineer would have responded to the same engineering goals with at least that same sort of solution.... which to me makes the idea not patentable. Of course who ever said that the USPTO ever made sense on what they considered for a patent.

    3. Re:Sounds good. by Runaway1956 · · Score: 4, Insightful

      I had the same thought - he's probably not saving fuel by turning off the ignition at a stop light. But, I didn't want to commit to actually TELLING HIM that he's wasting fuel. Just maybe, some manufacturer has come up with a more fuel efficient method of restarting a hot engine or something.

      But, yes, in most vehicles, it is going to take more fuel to restart the engine than to just wait for the traffic light. Someone told me once what the break-even point was, but I don't really remember. 3 minutes? Maybe a bit less. It probably varies for different size engines, and different idle speeds - in fact, it's probably different between automatic and manual vehicles.

      Personally, I'm not about to turn off an engine unless I KNOW that I'm stuck for 5 minutes or more.

      --
      "Windows is like the faint smell of piss in a subway: it's there, and there's nothing you can do about it." - Charlie Br
  4. Unnecessary if.... by ktappe · · Score: 4, Insightful

    This patent would be much less necessary if cities would install intelligent traffic lights that allowed traffic to flow and thus minimized idling engines.

    --
    "We can categorically state we have not released man-eating badgers into the area." - UK military spokesman, July 2007
  5. Great Idea, But... by iYk6 · · Score: 5, Interesting

    This is a great idea. But it's being done the wrong way. Rather than sending signals to start and stop cars, the traffic lights should just send signals saying how long the red light is going to be, and while they're at it, specify how long the green lights will be too. Then the smart cars should interpret that how they will, by stopping, starting, or showing a light to the driver. This method will upgrade smoother and be more resistant to jokers with toys at the intersections.

  6. IBM favors patent quantity over quality by FlorianMueller · · Score: 4, Informative

    ...if you don't ignore the fact that this is a blatant case of "patenting the goal". The patent is "here's a bunch of ideas that might work to control fuel consumption at signals, we claim them all."

    I agree that that this isn't really a fully-disclosed invention. Generally, IBM is more interested in patenting as much as possible just to create patent thickets and later shut out or tax real innovators with bullying tactics. The blog post I just linked to also mentions IBM's claim (made in early 2009) to have a number of patents "larger than those from Microsoft, HP, Oracle, Apple, EMC, Accenture, and Google combined." The blog post also mentions research that shows the average commercial value of an IBM patent is fairly low as compared to the portfolios of such competitors as Microsoft. The patent that gave rise to this slashdot article may be another example.

    IBM has also been a long-standing aggressive force in pushing the envelope concerning the scope of patentable subject matter in the field of software. Courts can't be lobbied the way politicians are lobbied (which is something at which IBM is also extremely aggressive) but companies can try to bring up court case after court case pushing the envelope with new arguments in order to find loopholes to extend the range of what's patentable. The recent landmark decision in Germany, effectively lowering the bar for software patentability in the largest EU member state, was related to a Siemens patent, but other landmark cases in the US as well as in Europe (at the level of the European Patent Office as well as in individual European countries such as Germany) related to legal recourse sought by IBM in order to obtain patents on "inventions" of an ever lower standard.

    At the lobbying front, the FFII (a European non-governmental organization fighting software patents and pushing for open standards) listed IBM as one of the four IT companies pushing hard for an overall patent and patent court reform in Europe aiming to strengthen the rights of patent holders and the legal basis for software patents.

    This doesn't mean to say that IBM is the only company doing it, let alone the only one with an interest in this, but others entered the game relatively late and IBM has a history of decades of pursuing that agenda of an ever broader scope of patentable subject matter.

    1. Re:IBM favors patent quantity over quality by Teancum · · Score: 3, Insightful

      One of the largest reasons for having such a huge patent portfolio is mainly to discourage patent trolls from trying to sue IBM. Especially if it is another manufacturer they can shut down competition that goes after them in the courts by throwing up enough other patents to make it a patent war on a large scale. So from a defensive standpoint, IBM is merely doing a good business practice by taking a bad system and trying not to get harmed by it.

      I've never really understood the patent system in the first place, as it really doesn't protect "the little guy", in other words the lone tinkerer in a garage who comes up with some crazy idea and wants to earn some bucks from the concept. Until anybody can show that such a person is legitimately protected, I have to consider the patenting process as something more of a scam that is designed to extract money from those who are least able to afford it. For a private person to patent something, I would consider it to be 99% of the time to be an utter mistake.

      For a corporation that already has full time lawyers working for them, having some of that legal time engaged in dealing with patent protection perhaps makes some practical sense. In other words, this is a system that mainly protects those who already have money and not those struggling to get some in the first place.

  7. How long until its hacked? by KDN · · Score: 4, Insightful

    Anyone want to take bets on how long until the protocols gets hacked and spoofed?

    • Go to a freeway overpass and aim it at oncoming traffic and see how many cars come to a halt.
    • At a real intersection keep transmitting the "off" signal at a higher power output than the real transmitter keeping everyone stopped.
    • car jacking potential?
    • Will this stop police cars in hot pursuit?
    • Will this make cars unable to get out of the way of a police car at a stop light?
    • Programming bug prevents the traffic light from switching. We've all been at those lights that get stuck.

    This should be a good thread on comp.risks.

  8. Re:And in other news... by BasilBrush · · Score: 3, Insightful

    Seriously... Great idea in theory. In practice, how many times have you sat waiting for a light and suddenly had to move NOW? Either for an ambulance, or some moron going too fast and turning far too widely, or a tractor trailer at a tight intersection that would otherwise have rolled its back tires over your hood, or even suddenly having to run the light to avoid getting rear-ended by someone coming up behind you completely oblivious to the light?

    In 20 years of driving, only the emergency vehicle one. I've never had any of those other situations. That's not to say they don't happen, but I am left wondering why you imagine they are common occurrences that happen to everyone.

    Secondly, I wonder why whenever a new idea/patent/invention is brought up here, some people object to it on the basis of assuming that the worst possible implementation is the one that would be done; that the inventor hasn't already considered the problems that come into your mind within seconds of hearing the idea, and dealt with them. And that an implementation would be continued with if such problems remained.

    a sizable number of people already do switch off their engines if they are in a quene of traffic and are going to be waiting a long time. And this doesn't seem t have caused problems. So there doesn't seem to be a problem with switching engines off in queues per se.

    A rational implementation would of course not switch the engine off unless the car was already stationary with the parking break applied. And it would not stop the driver from restarting the engine with the ignition key if needed. These obvious details seem to deal with all your fears.

  9. Environmentalist's wet dream by sycodon · · Score: 4, Insightful

    The ability to turn cars on and off at their whim.

    How long until one hacks into the system and just turns them all off?

    --
    When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
  10. This == overthinking the problem by bdleonard · · Score: 3, Insightful

    All this is necessary to achieve this is wider application of so called "mild hybrid" technology. Think over-sized battery, over-sized starter motor, over-sized alternator, drive by wire throttle, and a bit of ECU smarts. Any time the car is stopped (or below speed X, where X is small 3mph? ) the engine is "off" (no fuel, no spark, engine still turning if the car is in motion), and the battery and starter motor move the car. Once the speed threshold is exceeded (or battery is sufficiently low) fuel and spark are resumed. At any greater speed the vehicle is powered entirely by the engine. Having electrically powered accessories (power steering assist, air conditioning, brake booster, etc.) would be preferable, so that all of those systems still function when the engine is not spinning. It addition, making these electric tends to increase efficiency and reduce weight. If these systems remain belt or vacuum driven there can be many situation where the ECU may be forced to leave the car idling, or waste battery power spinning the engine to keep the accessories running.

  11. Re:For workers revolution! Smash imperilaism! by couchslug · · Score: 3, Insightful

    "Workers to power!"

    That doesn't "work" very well in practice, and couldn't even compete with the Capitalism you hate in terms of worker benefits. Eating the rich is great fun until you run out of rich to eat, then everyone else goes on the exploitation menu, for the good of the workers, of course.

    Capitalism leavened with a humane but not overpowering dose of Socialism arguably produces the best results. Business should be restrained by government, government restrained by business, and both restrained by the votes of an engaged and informed citizenry. Makes a lousy slogan though.

    --
    "This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
  12. There are technical issues, but they are ignored by netsavior · · Score: 3, Insightful

    Stopping cars at the light isn't all that hard, but making it a good idea to stop them at the light is pretty far away. The trivial problem of pre-loading the oil pump so that it does not do serious life limiting of your engine is a small detail that nobody seems to care about (because they don't know that starting and stopping conventional vehicles at every intersection is murder to the lubrication system, and therefore the entire engine.) Some cars do this (prius, some police cruisers) but most do not.

    Much more, you have to re-engineer cars so that A/C is not dependent on the motor running.

    Many people who live in places without shit weather have no idea about this (particularly California where "green" ideas that are wildly impractical seem to come from).

    Are there places in the country where you can freeze to death if your car stops? yes. Are there places in the country where infants can die of heat stroke if your car stops? Yes. those places just don't happen to be in California/NY.

    Heat and A/C are not about comfort, they are about survival, at least in many places in the country.

  13. Re:This may mess up right on red or end up like To by Rick17JJ · · Score: 3, Insightful

    I have encountered traffic lights which never turn green for my direction, even after waiting through many cycles for about 5 or 10 minutes. There was one light in town which seemed to be wait for its buried magnetic sensing loops to detect at least two cars to arrive before it would turn green. I would be coming back from a grocery store at about midnight and have to sit there for about 5 minutes while waiting for another car to arrive, then it would finally change. Unfortunately, there was also a no right turn sign at the intersection, which made it impossible for me to legally escape from the situation.

    There were three lights in town, more or less, like that. I have wondered if perhaps something about my pickup truck or the way that I approach the intersection, fails to trigger the buried magnetic sensing loops. I once talked to another local resident who had the same problem, in his pickup truck, with one of the same traffic lights.

    I would hate to encounter a traffic light which could turn off my engine in that situation, preventing me from backing up or turning right to escape the problem. Would there be an emergency override switch for the system? Would they require such a system being retrofitted to my older 1992 pickup truck? I also wonder what would happen if the power to the traffic lights goes out during a thunder storm. Would our engines default to start in such a situation, so that we could treat the failed traffic lights as 4-way stop signs?

  14. Drivers, traffic lights, and sensors by dtmos · · Score: 4, Informative

    IMHO the biggest problem with traffic lights isn't synchronization; it's the behavior of the drivers. At least in my area the lights are attached to inductive sensors placed in the tarmac, and the way they're supposed to work is that they sense the presence of the car approaching the light and, after a suitable period of wait time hysteresis (which starts from the last time the light switched, and so may already be expired), switch the signals and allow the car to pass.

    Unfortunately, drivers (again, at least in my area) aren't very clueful about the presence of the sensors, and will stop way, way back of the stop bar, before they get to the sensor, or pass over it and stop halfway into the intersection. The sensors are huge, roughly 2m by 8m, so it's not like you have to be precise to hit them, and they are visible as grooved loops in the tarmac just behind the stop bar, but I can't count the number of times I've been stuck behind a long line of cars at a light, with the first car stopped before it got to the sensor. As far as the light can tell, there's nobody stopped at the light, so we wait and wait.

    I've driven with people who have stopped before the sensor and then complained about how poorly the lights are "synchronized." Apparently, traffic light sensors are not common knowledge.