Questions. I have questions.

  1. I was driving home at just about 5:00 p.m. on Monday. Daylight Savings Time had just ended. The sun was very low on the horizon. It had fallen behind the treeline and the sky was partly cloudy. In general, it was still bright and very obviously daylight out. Everyone had their headlights on, though. That part doesn’t bother me. It’s better to err on the side of caution, after all. But if it were the same time of day with rain pouring down from the sky, at least one in six of those cars would not have their headlights on. Why is it they remember their headlights in broad daylight, but not in the rain? (And, seriously, I’ve counted cars on the highway in the rain before. It averages one in six who don’t put their headlights on. Sickening, isn’t it? That’s been the law since the dawn of time. . . )

  2. Why don’t we have “smart” traffic lights yet? For example: It’s 1 a.m. in your small town with one traffic light. As you approach it, the green light clicks to amber and then red. You’re stopped at a light that won’t turn green for another minute. But there’s nobody else on the road for miles. Yet, you’re stuck. You can’t run the red light, because there’s a cop in the parking lot on the other side who wants to meet his monthly quota with your help. Why can’t the traffic light see that there’s nobody else coming for miles around and flip your light green?

Another example: It’s 5 p.m. and the big corporate campuses just let out. Traffic streams onto the street towards a large four way intersection. It’s so far backed up that people can’t get into the left lane to make the delayed green left hand turn. If nobody can get to the lane, why is that lane’s green light still on? Why not turn the light green in the opposite direction to let people start going early?

I don’t know the technical solution for all this, though I’m sure it would be expensive and require massive amounts of testing for safety’s sake, but c’mon. We’re smarter than this, aren’t we?


 
 
 

11 Responses to “Questions. I have questions.”

  1. Soon
    6. November 2005 at 20:33

    I’m sure that according to the roads authority operating those lights that don’t turn green even though you’re the only one on the road, it’s seen as a success.

    Could also be that the magnets under the road are waiting for more cars. Have you ever tried backing up and rolling up to the line again to see if anything different happens?

  2. Mark, the Traffic Guy
    7. November 2005 at 07:14

    If you’re REALLY interested, I can post a couple of lines on how signals and detectors work (and its NOT magnets, Soon).

    Lemme know.

    You can also go to a website run by a fellow Raleigh-ite (Raleigh-onian? Ral-lite?): http://auto.howstuffworks.com/question234.htm

    Great site that you can waste hours in.

  3. Soon
    7. November 2005 at 16:43

    Oh, do post, I’ve been wondering what the hell they have underneath those scar marks on the roads.

  4. Mark, the Traffic Guy
    8. November 2005 at 09:46

    OK! Here goes… And, by the way, Soon, you weren’t too far off with your “magnet” theory as you’ll see below:

    Traffic signals are typically controlled by several pieces of equipment inside a metal cabinet installed at one corner of the intersection, including a controller, which is a microprocessor that runs the timing patterns and special programs that illuminate the traffic signals and pedestrian signals. The intersection can be run in different modes:

    -Pre-timed modes – where the signals run according to special timed patterns. This is common in urban intersections where there is always a large amount of traffic. Controllers can also run different patterns at different times of the day to reflect changes in traffic density at say, rush hour vs. mid-morning.

    -“Actuated” modes – where the signal timing patterns are affected or triggered by traffic detectors. (present-day controllers are smart enough to change the timing patterns continuously based on how much traffic is detected)

    By far the most popular form of traffic detection is the Inductive Loop Detector. Those “scar marks on the road” are small rectangular trenches cut into the asphalt. A special cable is laid into the trench and looped around (anywhere from 2 to 6 times), then covered with sealant. Both ends of the cable are run back to the controller cabinet and connected to an Inductive Loop Detector. This detector sends a electrical current through the cable. This current creates a magnetic field that extends from the road level to 1 or 2 feet above the roadway. When a large metal mass (like a car) passes over the loops, this magnetic field changes. The detector senses the change in the field and sends a signal to the controller, saying in effect “There’s a car here!” The controller then runs a timing pattern to change the signals to give the car “the green light”.

    So, it doesn’t have anything to do with the weight of the vehicle. Its operation also explains why motorcycles and large trucks are sometimes not detected. Motorcycles may either not be positioned directly over the loop nor have enough metal to change the magnetic field enough to be detected (tell your biker friends to put their bikes directly over the loop for the best chance). Large trucks have a large metal mass, but the truck bodies may be so far above the road that they do not change the field.

    There we go. Sorry you asked, yet?

  5. Augie De Blieck Jr.
    8. November 2005 at 11:15

    I’m not sorry. Thanks for all the info, Mark.

    Now, do any of these systems use radar? There are some lights in the town next door to me that cause my radar detector to pin at the highest possible level. It’s only at the traffic lights that this happens. I’ve suspected that the lights have little detectors to see when cars are near, using radar. Am I that far off?

  6. Mark, the Traffic Guy
    8. November 2005 at 12:36

    Augie, Microwave detectors are occasionally used (that might be what’s setting off your detector) along with video detection (the video detector is programmed to detect a change in pixel color at pre-specified blocks in the picture).

    The detector won’t be in the light, though. It’s probably mounted to one of the nearby poles.

    There are even detector systems that detect special strobe flashes from oncoming emergency vehicles to give the vehicle the quick right-of-way.

    By the way, I enjoy the heck out of your blog. Always keeps me and the guys at work entertained with what you find on the net. (You, and boingboing.net). Thanks!

  7. Soon
    8. November 2005 at 16:42

    Thanks Traffic Guy, that was really cool to read about.

  8. Jeff Wooten
    8. November 2005 at 17:03

    I gotta agree. This is a really cool thread. I had convinced myself that the DOT had programmed traffic lights to always recognize my car. I had also almost convinced myself that the quickest way to make a red light green was to pull out a newspaper and try to read it while I was stopped.

    BTW (and slightly off topic), Mark the Traffic Guy, You mentioned Raleigh in an earlier post. I live near Raleigh too, so my curiosity is working overtime: You’re not Mark Roberts the WRAL-TV traffic reporter are you?

  9. Traffic Guy
    9. November 2005 at 07:49

    >

    Auggggh! (Insert Charlie Brown head smack)

    I can’t stand that guy! He provides a valuable service to the area and does his job well, but his delivery is like nails on a chalkboard to me…

    I’m actually a techie who worked for several years in the Signals Management Unit of the North Carolina Department of Transporation, and still do a lot of consulting in the field.

    By the way, I do recall from my years there a “Jeff Wooten” being on the special “detect and impede” list, and there was a company working on a prototype detector that would scan driver’s retinal movements and switch to green when no one is looking so as to prompt a lot of honking and bird-flipping. There wasn’t a lot of interest at the time, but perhaps that’s changed…

    In order to avoid any more confusing, let’s just shorten my moniker to Traffic Guy! When you need me, just shine an alternating red, amber, and green light in the air…

  10. Jeff Wooten
    9. November 2005 at 09:23

    That’s funny, Traffic Guy! I didn’t want to say it in case you were him, but yes, he does have that nails on the chalkboard delivery. What’s even funnier (and please don’t be insulted) is that for a moment yesterday I even tried reading your posts with that voice in my head.

    BTW, I just KNEW there was a conspiracy. Now maybe I can be an honorary member of the Lone Gunmen…well before that “Jump the Shark” episode that is.

  11. Traffic Guy
    9. November 2005 at 10:19

    I just reread my posts with Mark Roberts’ voice, and, you’re right, that’s d@mn funny…

    Gotta go, head hurts…

    Let’s Keep ‘Er Movin’

    Traffic Guy
    (Honorary Trafficologist)

    PS. in case anyone else is wondering who the heck we’re talking about, check out the WRAL video feed at http://www.wral.com/video/index.html and click on “Work To Repair Portion Of I-40 Slated For Friday” to hear Mr. Robert’s dulcet tones (after the segment intro) (his bio is at http://www.wral.com/staff/460839/detail.html if you’re REALLY looking to duck productivity today)