Can we improve traffic safety and efficiency by eliminating traffic lights?

Wednesday, August 18th, 2010 by Robert Cravotta

I love uncovering situations where there is a mismatch between the expected results and the actual results of an experiment because it helps reinforce the importance of actually performing an experiment despite how much you think you “know” how it will turn out. System level integration of the software with the hardware is a perfect example.

It seems, with a frequency that defies pure probability, that if the integration team fails to check out an operational scenario during integration and testing, the system will behave in an unexpected manner when that scenario occurs. Take for example Apple’s recent antenna experience:

“…The electronics giant kept such a shroud of secrecy over the iPhone 4′s development that the device didn’t get the kind of real-world testing that would have exposed such problems in phones by other manufacturers, said people familiar with the matter.

The iPhones Apple sends to its carrier partners for testing are “stealth” phones that disguise a new device’s shape and some of its functions, people familiar with the matter said. Those test phones are specifically designed so the phone can’t be touched, which made it hard to catch the iPhone 4′s antenna problem. …”

The prototype units did not operate under the same conditions as they would in a production capacity, and that allowed an undesirable behavior to get through to the production version. The message here is never assume your system will work the way you expect it to – test it because the results may just surprise you.

Two recent video articles about removing traffic lights from intersections support this sentiment. In one of the video interviews a traffic specialist that suggests that turning off the traffic lights at intersections can actually improve the safety and efficiency of some intersections. The other video highlights what happened when a town turned off the traffic lights at a specific intersection. The results are anti-intuitive. This third video of an intersection is fun to watch, especially when you realize that there is no traffic control and there are all types of traffic, ranging from pedestrians, bikes, small cars, large cars, and buses all sharing the road. I am amazed watching the pedestrians and the near misses that do not appear to faze them.

I am not advocating that we turn off traffic lights, but I am advocating that we explore whether we are testing our assumptions sufficiently – whether in our own embedded designs or in other systems including traffic control. What is causing better traffic flow and safety in these test cases? Is it because the flow is low enough? Is it because the people using the intersection are using a better set of rules rather than “green means go?” Are there any parallel lessons learned that apply to integrating and testing embedded systems?

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12 Responses to “Can we improve traffic safety and efficiency by eliminating traffic lights?”

  1. E.V. @ LI says:

    Good point. You should consider other factors. Which contractor placed the lights and who ordered them? In Belgium 80% of traffic lights and signs are placed by the same company, sometimes at several intersections just 200 m apart. So who benefits? The supplier of course and the pay-offed ones in the middle. And then you also have the “green” ones who think that by making traffic a queuing nightmare, people will switch to public transport (that also is queued up in traffic). The result is only a huge economic cost and tons of CO2 extra.
    Sometimes, the lights are broken and what you then observe is that most of the traffic jams disappear. Why because people are smarter that some dumb electronic timers. Traffic regulates itself even if it looks chaotic but that’s not what traffic bureaucrats can imagine.
    If traffic needs to be throttled, install a circular roundabout. It has a lot less “conflict points” where accidents happen and has a higher throughput. teh Uk is master in these things. They even have “nested” roundabouts.

  2. B.C. @ LI says:

    I spent years working at Big Blue doing functional test verification. I have moved from testing to developer. As a formal test engineer, you can say yes, the unit test or function test pass, but behavior is undetermined until the system is completely SYSTEM tested.

    That is where side-effect issue show up and a formally passed and unit tested module will fail. I am always amazed by system test results. It’s always “Wow, I did not expect that!” There is no substitute for system testing nor stress testing.

  3. E.V. @ LI says:

    Fully agree. As CEO/CTO of my own company I stress that the first tester is the developer, not the test engineer, but that after the test engineer I will execute the idiot test to avoid that this role becomes executed by our customers. It is sometimes amazing how in a few minutes my “idiot” test reveals issues (mainly applies to GUI’s).
    Engineers often need to learn the hard way that good engineering is team work. The team must also include also non technical people.

  4. N.E. @ LI says:

    Here in Seattle we about as dumb as sheep. Every left turn is guarded with a “green arrow”. Rarely is there an option to turn left on “generic green”, yielding to oncoming traffic. And when there is such an option the average “Joe driver” does not understand the term yield to oncoming traffic.

    Left-lane Interstate drivers poking along with a delta-V of barely 0.5 mph over the traffic they are passing – if they are passing at all.

    In my estimation, our traffic mess is the sole result of comatose sleep-driving. Take away the traffic signals here and you get mayhem. It happens, we get power outages and the traffic backs up for miles. Left to decentralized decision making, here in Seattle, no decision gets made.

  5. L.H. says:

    You pose an interesting juxtaposition of “antenna-gate” and the messages to be drawn from some news pieces about removing traffic lights.

    Mistaken assumptions about the real world are just one of the forces illustrated here. As is often the case with news reporting, however, there are additional forces at play.

    An important force is that of ideology interfering with engineering judgement. The first video made no effort to hide its libertarian message. Clearly that’s social, yet there are other social values that traffic lights do support. For example, the ticketing of red-light runners provides a basis for shifting insurance costs to the people who make riskier choices. Stop lights also provide a solution to certain problems, such as when traffic is dramatically heavier on one road than another, by ensuring that the busy road doesn’t completely block the quiet road. In short, “are stop lights good or bad?” is presented ideologically, and therefore forces sub-optimal decisions in both directions, a problem that ideologies are notorious for.

    Another force is inertia. A stop light, design, or validation procedure may be perfectly fine until circumstances change. Traffic patterns change by time of day, season, growth era, even by isolated events. While traffic lights are fixed in their location, a whole other set of changing circumstances affect mobile devices: e.g., vehicles of motion, altitude, population density, geopolitics. An inability to anticipate and adapt to varying circumstances thus is a force in creating solutions that are, or eventually become labeled as, bad.

    I must also say that the inadequate reporting left me asking, “So, how does removing stop lights compare with other solutions, such as roundabouts, stop signs, congestion charges, bypass roads, etc.?”

  6. A.P. @ LI says:

    I have several “uncontrolled” intersections along my daily commute (i.e, they have stop signs instead of signal lights). I continue to be amazed at how few people actually know how to handle these intersections. They not only do not know the “rules” for how to behave in these situations but seem to have no common sense with which to figure them out (and these “rules” are little more than common sense to begin with). Several times, only quick application of brakes have kept me from ending up in an accident as someone either runs the sign or makes a left turn in front of me.

    I’d hate to see what it would be like in a big city instead of this small one.

  7. AIF @ LI says:

    I read somewhere about proposition to replace stop signs with “yield” and a demonstration how this speed up moving thru the intersection not even talking about saving lots of gas.
    I was pleasantly surprised how well “roundabouts” manage traffic in England.
    Here in MA we have quite a few rotaries mostly of the older construction before lights appeared everywhere.
    This are good ideas overall however I don’t believe it is doable with the menace drivers we have – young females on SUVs who never yield to anybody or put away their cell phones.

    We also getting European-style “green wave” in some towns when lights are timed to be green all the way if you drive at speed limit. I could remember these things in Europe from late 70s, so it took them 30 years to cross the pond. My guess because timing lights together requires installation of signal wiring between intersections which drives up project costs.

  8. M.F. @ LI says:

    Roundabouts are much safer and less stressing for the drivers than traffic lights. And as E. said above, in normal traffic conditions the drivers have to wait much less.

  9. D.W. @ LI says:

    New York has had coordinated signal systems, where you can get all green lights when traveling at the speed limit, for many years. In the 90s they installed a more sophisticated system, similar to the one installed in Los Angeles for the 1984 Olympics, which uses a computerized control center which gets input from senors at intersections and cameras to control traffic patterns. There is also such a system on Long Island, and probably other places in the U.S.

  10. D.A. @ LI says:

    In Naples, there may as well be no traffic lights – everyone ignores them. How well it works compared to other systems I don’t know, but traffic eventually moves and pedestrians survive somehow.
    We have some roundabouts in Boston and they work well for light traffic. However, many cities have added traffic lights to busy round-abouts, so they don’t work in all situations.
    In Minneapolis they meter the freeway on-ramps – this increases the chances that they can keep traffic from reaching the “stop and go” stage – hence increasing the percentage of good flow.
    Seems that several systems work for light traffic – the challenge is to have things that work in heavy traffic – aside from using an alternative to cars driven by human beings.

  11. B.D. @ LI says:

    According to my friends in France, most of the traffic signs are Yield signs. Because the French don’t like authority, placing a stop sign at an intersection is done almost apologetically by the officials, and only with significant justification.

    I agree with Alex – I drive a lot in MA and the unwritten rule is that you need both a light AND a stop sign for people to realize you’re serious! Of course, MA is the only place I know that uses flashing green lights as a traffic signal….

  12. Jerry says:

    Can we improve traffic safety and efficiency by eliminating traffic lights?

    Yes, just replace the lights with roundabouts.

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