Traffic-Flow Algorithm Can Reduce Fuel Consumption

thecarchik writes "New projects from German automakers Audi and BMW promise to ease congestion simply by looking at traffic signals and driving style, in an effort to smooth the flow of traffic. Through a test course in Munich, vehicles were able to post phenomenal fuel efficiency gains simply by adjusting the timing of traffic lights depending on traffic volume — to whatever speed provides a so-called 'green wave' of four or more synchronized signals."

Comments

Re:It astounds me

[Garble Snarky]

Traffic timings don't even need to rely on cameras, they frequently take input from the inductive sensors (even more ubiquitous than cameras) in all four streets on the intersection.

Poorly designed vehicle detectors

[tepples]

With all the red light cameras everywhere (for safety), you'd think they could put a few out there that would make it so I don't spend 3 minutes every morning staring at an empty intersection.

A lot of traffic signals are on a fixed cycle because the sensors buried in the street often fail to reliably detect a bicycle waiting to turn left (US; mirror in UK/AU/JP), even when the bicycle's wheels are directly over the edge of the loop.

Re:Poorly designed vehicle detectors

[dougmc]

Then the sensors are faulty. Properly adjusted, they will reliably pick up a bicycle. Even a bicycle with a carbon fiber frame -- the wheels alone are enough to trigger a properly adjusted sensor.

In Austin, you can call 311 (the non-emergency line) and report an intersection where it doesn't work and they'll fix it in a few days.

Re:Poorly designed vehicle detectors

[dr2chase]

No no fucking no. They do not work that way. You want to align a large conducting loop or blade across the sensor's AC magnetic flux. It's looking to form a short-circuited transformer with the body of your car, or a bicycle wheel.

Re:Poorly designed vehicle detectors

[dr2chase]

Yeah, the magnet meme is widespread.

There's a web page that explains it in gory, but still somewhat EE-oriented, detail: http://humantransport.org/bicycledriving/library/signals/detection.htm

What you need to imagine is that there is a big stream of something flowing out of the top of the loop, around, and back in the bottom. Position your bicycle so that you put a closed conducting arc around the largest possible amount of that flow. For example, position a wheel on a wire, in the plane of the wire or tilted inwards towards the middle of the loop. That puts your wheel perpendicular to the "flow", and thus you cut a large part of the flow, and the detector will sense you.

Note that if you position your bike perfectly vertically in the dead center of the detector, you will intersect little or none of this "flow", and hence you will not be detected. If you lay your bike down flat on the pavement, you will detect a lot.

Some detectors have a figure eight configuration (two side-by-side rectangles, usually) and for those, the flow is directed from one rectangle into the other (over the line separating them). So for those, it is GOOD to be dead center and perfectly vertical, you will intersect a lot of the flow.

And electrically speaking, that "flow" is the alternating magnetic field caused by a current in the detector. Anything conducting that intersects the field, forms a transformer, and that is electrically different from not-a-transformer, and that is what the detector actually detects. It has to be a changing field; a constant, DC field (like a magnet) has no effect. If you knew the frequency of the detector (10-200 KHz, says the article) and moved the magnet back and forth across that wire that fast (10,000x per second) then the magnet would work.

See also: http://www.coolmagnetman.com/magpipes.htm -- a falling magnet is also a changing magnetic field.

So can making only right turns !!

[Anonymous Coward]

It's been proven buy Tory, Cary, and the other guy.

Re:So can making only right turns !!

[Hijacked Public]

And UPS

Re:The green light is "half empty"

[tepples]

BMW makes cars, which are not "green" by any standard. You want green, invest in buses, trains, bikes, etc. Not more cars.

This is pretty clearly a greenwashing attempt by BMW.

Yes, and I am OK with that...you see they do not make trains, bikes, (or even buses?)

I know BMW makes "bikes" in a sense, and another German car company makes buses and sold them in the USA until the 1964 chicken tax.

Hybrid or electric

[foniksonik]

Hybrid or eletric cars don't use any fuel while stopped or even during normal in city acceleration.

Re:It astounds me

[no1home]

As a motorcyclist, I run into this some as well, though they have improved greatly (or it's because I have a bigger bike now). I have been pulled over once in my hometown for running a red. I explained to the nice officer (she was hot too, BTW) that I had waited through three cycles of the lights and never was given a green for my left turn, so, when it was clearly safe, I went. She let me go. Now, I hear rumor this is legal, but don't depend on it. It might not be for your jurisdiction (or even mine). However, it might be legal simply based on the idea that the signal is malfunctioning and you must therefore take matters into your own hands. You can solve your problem with a rare-earth magnet stuck to the bottom bracket of your bicycle. I know some bikers who use it and it has helped them.

Re:It astounds me

[pearl298]

In Scottsdale Az the lights are deliberately set to stop you at EVERY intersection! WHY you ask? According to the chief traffic engineer "So you will be "encouraged" to stop and shop at the local businesses along the way!!" Yes I actually heard this from his lips! Although his head did seem a little strange from a bad case of "recto-cranial inversion". I NEVER shop in Scottsdale because of this!

Re:Red Wave

[eastlight_jim]

This policy was changed in 2009 when the Department for Transport realised the error of its ways. It now encourages more of a 'green wave' approach where possible.

Source

Re:It astounds me

[Anonymous Coward]

Five ways? P'shaw.

We got 6 way intersections with nothing but a few stop signs around here.