Computer Failure Causes Gridlock In MD County 483
Uncle Rummy writes "A central traffic control computer in Montgomery County, Maryland failed early Wednesday morning, leading to widespread gridlock across the entire county. The computer, which dates to the 1970s, is the single point of unified control for all traffic signals in the county, which comprises a number of major Washington DC-area suburban communities. When the system failed, it caused all signals to default to stand-alone operation, rather than the highly-tuned synchronization that usually serves to facilitate traffic flow during rush hours. The resulting chaos is a yet another stark reminder of how much modern civilization relies on behind-the-scenes automation to deliver and control basic services and infrastructure. The system remains down Thursday, with no ETA in sight."
All-green probably an urban legend (Score:4, Insightful)
Most of those boxes have a "conflicting green" detector circuit that automatically puts the signal in "safe mode" when it detects two conflicting green lights.
On simpler systems, "safe mode" is all-way flashing red lights.
I guess if you knew what wires to mess with you could disable this safety feature.
Physical access is root access.
Re:Where's a traffic cop when you need one? (Score:5, Insightful)
Wouldn't matter. The traffic lights were working fine, the problem was there was no central system that could take a larger view of traffic and sense that turning a light green a block away could prevent a gridlock issue at a specific intersection. Intelligent traffic control takes traffic that is approaching a heavily congested area and intentionally slows it down, while freeing up cars to LEAVE congested areas more quickly. They help prevent gridlock by making sure that once a specific light turns green you can actually drive through the intersection, and turns the light red BEFORE cars get caught in the middle of an intersection.
You see this kind of design a lot in well-designed roads in smaller towns. Busy towns will tend to have lots of stop signs coming in to town, but try to reduce stop signs when leaving town. The idea is to keep inbound traffic from filling the town faster than departing cars can leave by making sure cars that are leaving can do so as quickly as possible, while cars wanting to come in will be intentionally slowed down.
A meter maid has no more information about traffic flow at adjacent intersections than an autonomous single light would.
70s computer (Score:5, Insightful)
Damn! 70s? Talk about Return on Investment.
The WashPost, in another article touts Fragile Technology.
I reach for my 70's era calculator and estimate the operational life of 34 years for this system. Some Fragility. Who or what at the Post has been there that long.
Wonder if its some ancient PDP version or an small IBM mainframe. The article is scarce on details. Parts for either are getting hard to find except in the scrap market.
Still you have to wonder why it wasn't ported to some other platform if nothing else as an exercise in disaster preparedness. Any commodity computer could do the job.
There is a lot of stuff like this still in service. I saw a PDP 8 monitoring turbines in a hydro Power station, and asked about where they get that fixed. The reply was it never broke down, but they had stockpiled 6 replacements, tested each yearly, just because they realized how old it was. Nobody knows exactly what it does anymore.
Re:1970's computer (Score:3, Insightful)
Old systems stick around because they work. City-wide traffic systems are very complicated affairs. Getting rid of a 40 year old system also means trashing 40 years of hard lessons.
Re:When the system fails, shut the lights off. (Score:4, Insightful)
I mean, sure, the law states that when an intersection has traffic lights, and the lights are out, it's an all-way stop. But in practice, I rarely see other drivers actually give a fuck that they are supposed to stop.
Re:MontCo $$ (Score:3, Insightful)
Well, not since the tax-cut/reduce-government fanatics came into power.
Re:When the system fails, shut the lights off. (Score:2, Insightful)
When a traffic signal in Toronto loses contact with the computer, it goes to flashing 4-way red, to remind people it's an all-way-stop now. They only go to "no signal" if there's a power failure. (In which case, they're still all-way-stop but despite the radio saying so every time there's a power failure, 70% of drivers just blow through a dark traffic light at speed.)
I think all-way-stop on multilane roads are MUCH MUCH MUCH MUCH worse than untimed lights. People have no idea how to deal with multilane roads that have a stop sign; almost no-one will let a left turn through, all sorts of problems like that.
Re:When the system fails, shut the lights off. (Score:3, Insightful)
I have seen accidents at lightly trafficked intersections when the light was completely out... I don't want to imagine the apocalypse of a couple hundred all going out in a well populated area; it would turn into Mad Max in a matter of hours.
Re:This is reassuring... (Score:1, Insightful)
No one can see at that intersection
what are the red & blue lights on top of cop car for?
Re:MontCo $$ (Score:3, Insightful)
No one fixes infrastructure until it's broken. That's pretty standard everywhere.
Sometimes not even after it's broken. Or more commonly, when it's broken, there's a half-assed temporary repair that becomes the permanent repair until it breaks again.
The biggest reason for doing this is short-term-ism: If a politician manages to save money now, it doesn't matter to him that somebody else 10 years down the line will have to spend far more money to clean up the mess after the system failed. So each administration (at any level: state, county, and municipal governments are far from immune to this) tends to do it's best to pass the buck on to the next guy, and the easiest way to do that is to simply not do repairs until something breaks.
Re: Are you kidding? (Score:3, Insightful)
We have a few roundabouts. Believe it or not, frequently every entrance has a stop sign instead of a yield sign. Kinda defeats the purpose.
Re:I live there (Score:4, Insightful)
Time to break out the bicycle. Or walk it, for that matter.
6 miles should take about an hour and a half at a decent walking pace, or about 45 minutes at a fairly leisurely cycling pace, and a week or so of it and your new sculpted bod will drive the ladies wild. :)
Re:When the system fails, shut the lights off. (Score:3, Insightful)
People have no idea how to deal with multilane roads that have a stop sign; almost no-one will let a left turn through, all sorts of problems like that.
Maybe you should teach them this and test it on Drivers License exam instead of usual round the block with automatic transmission then, eh?
Re:Where's a traffic cop when you need one? (Score:2, Insightful)
That would be called "following too closely" around these parts. Doesn't matter that if you leave a 10 foot gap to the car in front of you that 3 people will try and cram their giant SUVs in there at once while talking on their phone.
Re:I've seen this movie as well... (Score:3, Insightful)
You must have seen the theatrical release. It was indeed bad, the unrated version was pure entertainment. It was almost all mindless action and a lot of good laughs, which were absent in the rated version ("Yeah, your girlfiiend's at the bottom of an elevator shaft with an SUV rammed up her ass"). And what movie ever gets anything at all right?
BTW, what's BPS? I looked it up in wikipedia and nothing seems to fit.
Re:And if they had been using roundabouts... (Score:5, Insightful)
As a UK resident and driver in the true home of the roundabout, I wish to tell you that roundabouts are not a panacea.
Roundabouts work best for light to moderate traffic, where all 4 directions and all movements (left turn, right turn etc) are fairly equal in demand. For heavy traffic, they very quickly congest as traffic builds on the roundabout and blocks all entry. Indeed, round here most busy/large roundabouts have traffic lights on them as well, with varying degrees of success.
As for "gas consumption from forced arbitrary deceleration and acceleration is reduced" - I strongly disagree. Here roundabouts are used as a form of 'traffic calming', ie a deliberate obstacle to slow traffic. With a traffic light its a 50/50 chance between stopping completely and carrying on at cruising speed. With roundabouts there is always a decelerate/accelerate cycle, which depending on the design of the junction can be quite severe. In Birmingham (UK) and elsewhere. there was even a recent fad among local traffic engineers to plant high vegetation on the sightlines for approaching traffic to force all vehicles entering the roundabout to slow to below 5mph to be able to see traffic on the junction. On some examples here you have maybe 3 ft before the roundabout itself where you can see oncoming vehicles.
Don't get me wrong, I'm not saying that roundabouts are rubbish and traffic lights are good, but theres different solutions to different problems. Replacing non-synchronised traffic lights with roundabouts in a situation with very heavy traffic would have a very much worse result.
Re:Where's a traffic cop when you need one? (Score:3, Insightful)
Hmm...around here it means HIT THE GAS, otherwise you're gonna have to stop soon!!
Re:Where's a traffic cop when you need one? (Score:2, Insightful)
Redundancy! (Score:2, Insightful)