What to do about powerless traffic signals

[jwolfer]

^ The problem comes in how often the sign would be applicable. Ideally, the signal is rarely dark...is a sign needed for so rare a circumstance.

Signs aren't always the best solution...

I know here in Florida there are a few big intersections with battery back up.  But we get lots of summer T-storms w power out for a few minutes.. The batteries would run out if power off for days.  But when we had hurricanes knock power out a few years ago.  The Shierffs dept had officers out pretty soon after winds died down

[1995hoo]

A lot of people learned to pump the brakes and don't understand that with ABS you don't do that.

except when your ABS does not kick in, in which case you do need to pump manually, at least once.  I stopped myself from skidding into a busy intersection in Fairbanks this past March by doing precisely that.  I don't know why the ABS didn't kick in, but then was not the time for philosophical discussion. 

the more general lesson taught should be "if your brakes lock up, release and try again", which resolves to "pump brakes when no ABS" and also to "if ABS is working, keep foot depressed".

All a fair point. What I was thinking of when I typed my post is how several people I know have said, "I think I messed up my antilock brakes because the pedal started vibrating, so I took my foot off."

[realjd]

A lot of people learned to pump the brakes and don't understand that with ABS you don't do that.

except when your ABS does not kick in, in which case you do need to pump manually, at least once.  I stopped myself from skidding into a busy intersection in Fairbanks this past March by doing precisely that.  I don't know why the ABS didn't kick in, but then was not the time for philosophical discussion. 

the more general lesson taught should be "if your brakes lock up, release and try again", which resolves to "pump brakes when no ABS" and also to "if ABS is working, keep foot depressed".

To hazard a guess as to why your ABS didn't kick in - my first thought is that all four of your wheels locked up. The car doesn't know its own speed; it only knows how fast the wheels are turning. Usually the assumption that wheel speed = car speed is correct. ABS works by detecting differing wheel speeds while braking. If all four wheels lock, the car assumes it's happily stationary even though in real life it's careening into traffic.

[agentsteel53]

To hazard a guess as to why your ABS didn't kick in - my first thought is that all four of your wheels locked up. The car doesn't know its own speed; it only knows how fast the wheels are turning. Usually the assumption that wheel speed = car speed is correct. ABS works by detecting differing wheel speeds while braking. If all four wheels lock, the car assumes it's happily stationary even though in real life it's careening into traffic.

I did not know that, but that is a sensible guess.

I wonder how to solve that problem.

1) deceleration of wheels occurred far too quickly compared to known values for how well the car brakes - wheels must be locked up, or car has crashed into a wall.
2) add an accelerometer which detects change in velocity of the moving body and compares it to change in velocity implied by rotation of the wheels.

[kphoger]

Totally as an aside, but my father learned only a few years ago that one of his uncles was the inventor of ABS.  He sat on the invention while the big car manufacturers offered him peanuts for his idea, and only jumped when the right deal came along.  My dad remembers going on childhood visits to his uncle's house in the Michigan dunes–a huge house overlooking the lake, obviously (looking back now) a rich man's house–but never really thought anything of it as a kid.  Now, of course, it makes sense how he could have afforded such a place when the rest of the family was of more modest means.  Anyway, over time, my dad gradually became less connected to his Chicago-area family and didn't really know the guy anymore.  But, as my grandfather was nearing the end of his life, it's amazing what family stories started coming forth.  For the life of me, I can't remember my dad's uncle's name; it might be rather hard to find in the history books, since I assume the bigwigs in Detroit ended up taking most of the credit....

[MASTERNC]

Wisconsin has the practice, at least for state highways, to place folding stop signs at signalized intersections which can be unfolded and displayed in case of a power outage.

I've seen a couple of these in the Philly area.  It depends on the road and the township.

One township (Radnor) actually brought in portable generators last year after Hurricane Irene and attached them to the traffic lights at major intersections.

[colinstu]

I've seen the folded stop signs all over WI... I just kinda assumed that was a thing outside this state too... apparently
not!

35th St and National Ave http://goo.gl/maps/1ijRh however didn't feature such folding signs when they needed to mess around
with the metal box that has some traffic light tech inside it back in the summer. The first day it was a 4-way flashing red
stop, the next day they had stop signs installed all over the place and turned the lights off while working inside the box.
Day after that the lights were back to normal and stop-signs removed. The traffic here wasn't bad at all in the morning but
in the afternoon it was BAD. Traffic on the viaduct backed up like half way or a third of the way. The problem was the two
lanes from each direction stopping... people turned into scaredy cats here and most people didn't move fast enough.

I remember Capitol Dr and Humboldt http://goo.gl/maps/MqyDD back in the spring randomly turned into a 4-way flashing red
stop too during the day. It actually worked out pretty damn well. Everyone stopped and gave way like they were supposed to
and seemed to work better than the signalling that's usually there.... but that's because Humboldt isn't very busy of a
road, and when there is traffic to turn left onto it, or cars on humboldt at all... it's only a couple cars.

Here's some interesting videos:
Auckland power cut... 3-way intersection working pretty well w/o lights and drivers don't treat it like 3-way stop: http://www.youtube.com/watch?v=Q3-MspHo7ZI
UK project to turn off their seemingly useless traffic lights with nice results: Part 1 http://www.youtube.com/watch?v=lBcz-Y8lqOg Part 2 http://www.youtube.com/watch?v=vi0meiActlU

Got a little off-topic here, but in WI anyway people are pretty good at treating it like a stop sign. Although I can't say I'm always a fan of traffic lights. I wish left turns on red were permitted (after stopping of course and yielding to traffic). Also wish red lights would act like a stop light at times too... sitting at a red light with NO cross traffic drives me insane... I should be able to stop, look left and right, and proceed. Basically I'd like the major road to be flashing yellow with the minor road being a flashing red.