Interesting idea about platform edge lighting

[SchuminWeb]

Here's an article about an idea to upgrade the platform edge lighting:

http://transport.kurtraschke.com/2011/06/improved-metrorail-platform-edge-lights#comment-1297

Interesting idea, indeed, though not a good one, especially when you consider that the platform edge lighting is pretty much obsolete these days.

[WMATAGMOAGH]

I'll let John post all the details but originally the lights were going to only flash in the center of the platform if a shorter train was arriving.  This is an interesting idea but far too cost prohibitive in my opinion, when the next generation PIMS signs arrive, perhaps they can install more than one per platform at each stop.

[SchuminWeb]

My understanding is that "The Metro Channel" (the next-generation PIDS) will exist alongside the current PIDS for the foreseeable future.

[Tritransit Area]

Hmm...the new "PIDS" will be like a regular TV monitor or something like that?

They really probably should've gone with Amber lights for the platform edge, btw.

[Sand Box John]

Oren pretty much explained it in simple terms.

The lights were to flash at a higher brightness along the platform where a train less then 6 cars long would stop. The rest of the lights would flash at a lower brightness. The same applied when trains of 6 cars or less were programmed to stop short or long of a center platform stop.

The lamp fixtures along a platform are wired in 8 circuits with 18 lights per circuits that are 75' long each. Half of the circuits get their power from the AC switch board room at one end of the platform, the other half from AC switch board at the other end. The 4 light brightness controllers are driven by the platform light flashing module in the station train control. 

The problem with this schema is the existing LED lamps are screwed into conventional 120V porcelain lamp sockets mounted on a 4X4 hexagonal junction box imbedded in the poured in place concrete platform slab.  The lamp sockets face the track on a center line that is roughly 6" below the surface of the platform.

All 26,496 of the 6 1/2 X 2 inch glass dicks would have to be replace as the existing disks would dissipate the detail of graphics coming from the RGB LED arrays, also the diameter of hole under the glass disks are roughly 2 smaller.

A lot of the hardware to control the RGB LED arrays is already in place. The big bucks is in replacing the existing glass disks with imbedded RGB LED array disks and the associated low voltage lines to control RGB LED arrays.

[WMATAGMOAGH]

I agree with Brandon, I preferred the amber LEDs they tested out at Gallery Place.  I also would have liked to see white LEDs.

[Tristan]

Wasn't it said that the red LEDs were cheaper than the ambers?

[79MetroExtraMD]

Wasn't it said that the red LEDs were cheaper than the ambers?

I thought that was the case too. Plus, it gives more of a warning color than with amber.
Also, I think they should replace the translucent glass covers with transparent ones to make more of the light shine through. Just my dos centavos.

[WMATAGMOAGH]

Red and amber were the same cost, white was more expensive according to http://www.wmata.com/about_metro/news/PressReleaseDetail.cfm?ReleaseID=1559.  I can't find the quote online, but I believe Catoe was quoted with the red light decision as saying he chose red because "red means stop" so people wouldn't stand by the platform edge. 

[Sand Box John]

79MetroExtraMD
I think they should replace the translucent glass covers with transparent ones to make more of the light shine through. Just my dos centavos.

The disks are translucent to defuse the light coming from the lamps. If they were transparent you would only see the light if you were looking straight down at them, as it is now the brightness of the lamps is same regardless angle of the viewer. Also if the disks were transparent the light from the lamps would projected upwards and reflect off the underside of the mezzanines, the vault arches and platform canopies.

[SchuminWeb]

Also, I think they should replace the translucent glass covers with transparent ones to make more of the light shine through. Just my dos centavos.

I think the bigger problem is that since switching to the red LEDs, the difference between high and low is too little.  Some platforms' lights go entirely to black when they're flashing, and that's a pretty good solution to the problem.  Thus they're flashing on and off, which is noticeable, vs. the little variation before, which one has to look for to notice.

BTW, has Metro changed any more bulbs to red since Catoe left?  Glenmont for one is still original, and I'm pretty sure a number of others are, too.

[Sand Box John]

SchuminWeb

I think the bigger problem is that since switching to the red LEDs, the difference between high and low is too little.  Some platforms' lights go entirely to black when they're flashing, and that's a pretty good solution to the problem.  Thus they're flashing on and off, which is noticeable, vs. the little variation before, which one has to look for to notice.

That's one of the properties of LEDs. When the voltage coming in drops below a certain threshold LEDs go dark. The proper way to very the brightness of LEDs is to power them a full voltage multiple times per second. The brightness changes depending on the number of times and the length time power is applied per second.