Monday, January 04, 2016
Question for the audience
If you drive in the Twin Cities, have you noticed that a lot of the overhead lighting on the expressways seems to be turned off at night? I have noticed that all the lights on the 35W bridge over the Minnesota River aren't being turned on -- I've seen this during my morning commute and noticed it as we were coming home last night. I also noticed that on various stretches of 35W elsewhere in town, it seems as though only half the overhead lights are in operation. This seems like a dangerous idea and I haven't seen any public discussion of the topic. Anyone have any idea why this change has taken place?
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12 comments:
As a former lighting engineer, I can tell you that those little photocells on top the light fixtures sometimes fail. And I can tell you that some governments choose to save money by only installing one photocell per every so many lights, so when one of them fails, all of the lights connected to it go out. May or may not be what's happening here, but that's a possibility.
Thanks, Jerry.
Okay — so in the case of the 35W bridge over the Minnesota River, which level of government would control that? The river divides two counties (Hennepin and Dakota) and two communities (Bloomington and Burnsville). Would that be a state responsibility?
It seems to me that a conscious decision is involved, since I'm seeing decreased lighting in other areas of the metro as well.
in CA, this would fall under the responsibility of CalTrans, a state agency that manages the state roads. maybe you could call MinnTrans, or its equivilant?
maybe you could call MinnTrans, or its equivilant?
I will do that -- the agency here would be MnDOT.
I sent a note to someone at MnDOT -- will let you know what I find out.
I wonder if it's the photocell explanation (I've replaced a few outside light fixtures when those went), but on the flip side, my nicer hope is that someone is figuring out that lighting does not always help the situation. Sometimes it just shows exactly how much schmutz is on the windshield, no?
not only that, but lights cost money to operate and maintain. lets be conservative, ok?
my nicer hope is that someone is figuring out that lighting does not always help the situation.
I guess I'm confused why a dark road in the rain is preferable to one that is well-lighted, Bubba. And if the rain is obscuring your view, or if you're driving into a fog bank (a common occurrence on 35W in that area) I don't think schmutz on the windshield is the issue.
Again, most of the problem is that government doesn't pay much attention to what works or what is best from a science and engineering standpoint. There was a famous experiment down in Louisiana where they kept adding crushed seashell to the roads, to make them white, thinking that would reduce lighting requirements. It simply made matters worse because if you light the roadway and not the objects ON it, the maximum contrast possible is 1.0 (and realistically much less than that). If you light the objects on the road, preferably with directional lighting in the direction of traffic flow, against a black asphalt background, the maximum possible contrast is infinity (again with practical limitations). But government doesn't want to pay for highly controlled lighting, so they settle for the lights that put light both ways. What helps the cars in one direction glares in the eyes of people going the other way. Those tall poles at the cloverleaf intersections spill a lot of light, but do a pretty good job overall. Light coming straight down bounces off the curved surfaces of cars, just enough off the road and very little directly in your eyes. But pricey. Oh, and just so you know, driving at night on a wet, unlit asphalt road exceeds the processing capacity of the human visual cortex. You can't do it.
Gracious host, I think jerry summarizes the possibilities that might lead to lighting being comparable, or worse than, no lighting. Do things poorly, and you might as well not do anything at all.
Is that the case? I don't do enough driving in the Cities to tell, but I can tell you I've personally been in many places where the lighting at intersections and such just made things worse.
I'm talking about turning the lights off entirely. That's what is going on. There are mutiple lights on the bridge, but they aren't being deployed.
Also, the issue is not seeing the road when it's raining; it's being able to see the lane markers, which have reflective paint. Light helps you stay in your lane.
Jerry, I am sure you are correct about the mental acuity of our gubmint pals, but I do not see the advantages of turning the lights off.
You are correct, of course, that some light is (almost always) better than no light. My point is that governments sometimes try to save money at the expense of doing them properly. Lighting of the Metrodome went to the low-cost bidder but it's really poor. Now that "eyesore" is gone.
And I don't so much think it is a case of "turning the lights off." I think it is more a case of not attending to proper maintenance that would keep them on. A call to MNDOT reporting the problem should (if government were responsive and efficient :-/) result in the lights coming on. Dim bulbs occur, however, in places other than the bridge, and tend to be found most often in government offices.
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