Are the railways in the U.S.A. installing LED railway signals as upgrade or replacement for the normal filament lamp signals.
I have seen in New Zealand that on our Auckland railway lines quite a few new LED railway signals have been installed, at the double tracking of our West Auckland line.
Over the last few years i have noticed that most traffic lights are being upgraded to LED lamps for less maintenance and lower power consumption.
If not do these lamp signals have single or double lamp assemblies, in case one lamp or filament fails.
There are several applications of LED signals that I know of on Canadian Nationals ex Grand Trunk Western in Michigan. They are as follows: Southward Absolute Signal at Holly on the Holly Subdivision, Southward Absolute Signal at Andersonville on the Holly Subdivision, Control Point GRAND on Main 2 on the Shorteline Subdivision and the newly installed CTC section on the Flat Rock Subdivsion between Control Point Alice and Riverview excluding FN Interlocking which is controlled by Conrail Shared Assets.
The Signal Supervisior for this territory informs me that all new installations and upgrades will be LED’s. He feels, as you have stated, that they will require less maintinace.
The plus side for train crews is that the LED’s are bright enough to be seen in the daylight from a greater distance.
Have ya ever seen a fire truck or ambulance with those LED lights? Yeah, bright is an understatement. The upside is, you can see them from a long distance, even during the day, the downside: At night, wow… an ambulance passed me by on Weber Rd last night, all LED’s from roof to grille, and I was seeing spots…(I saw him coming from when I got off the I-55, and he must have been about 3-4 miles away, and there was no mistaking an emergency vehicle was coming) I am not sure, but does anyone know if the BNSF’s new signal bridges on the Aurora-Chicago main are LED or not? They seem to be alot brighter than the old “searchlight” signals on the older bridges that they are dismantling. What about grade crossing signals? The IHB installed some new ones near CP LaGrange about a year or so ago, again much brighter than the old ones, is that because they are new, or because there are LED’s inside? I have also noted that there are some traffic signals at a few intersections in my area that seem to be LED as well. Personally I like the LED type lights, much easier to see.
Those of you who live or travel near the EJ&E tracks from West Chicago to Joliet will be aware that the J is installing CTC between those two points and this includes LED signals…VERY BRIGHT INDEED!
LED light units are standard practice in the U.S. for new or replacement grade-crossing signalization. None of the Class Is I work with are presently using LEDs for wayside signals to my knowledge, except maybe on an experimental basis. But I’ll do some checking around tomorrow.
I’ve encountered an LED dwarf signal in the north throat of Chicago Union Station a couple of years ago–probably the same signal that is illustrated in Brian Solomon’s book on signals. It looks like an array of LEDs with all four colors are within the single head–only one color at a time is lit, of course.
LED’s are much more expensive up front. They save money in the long run via energy savings and time between replacement is up to 20 (IIRC) times longer.
On highway traffic signals, INDOT has a policy of not replacing the amber (yellow, if you will) with LED lamps because they are not lit enough to generate enough savings to justify the extra cost. RR’s won’t have that problem as the indications don’t change as often and quickly.
One advantage of LEDs is that they are designed (doped) to be very color specific. Red is RED. They are individually focused, and, as has been mentioned, if one fails, in most cases it won’t take out more than 3 or 4 of it’s neighbors (sometimes, to save some money and labor, they are wired with several in series, to get the necessary voltage drop across each).
On the other hand, I’ve found that the tinting at the top of my windshield can mask an LED red stop light to the point that I can just barely tell it’s illuminated.
Cost? Bulk retail usually has them around 70 cents to a dollar each, although I’m sure that really high quantities and wholesale drop that further.
Vehicle LED lights sometimes come with heaters in them for that very reason - and they are more likely to get covered with frozen stuff than RR signals…
An internal heating element has to be added to avoid that issue and can be thermostatically controlled.
The LED’s are certainly a lot brighter and the colour emitted is monochromatic, which means that the colour is from one wavelength only.
Purchase costs are a lot higher for LED’s, a cluster of 200 LEDs will cost well over $100 and in addition there is a current regulated supply which is set for a certain current flow through the LED’s.
A normal Red LED draws 20 mA’ at 1.7 Volts, a Green one 20 mA at 2.2 volts, Blue 20 mA’s at 3.3 Volts.Orange 20 mA at 2.1 Volts. These LED strings are connected in series parallel. I think similar principle is done as with traffic lights. strings of 4 LED’s in parallel then in series with the next and so on.
LED’s are low voltage, low current devices and arrays or strings are made up to get a large area for a signal.
Using LEDs in a 12VDC environment, one has two choices to get the voltage across each LED to the proper level. One is to put a dropping resistor on each LED, which is occasionally done, but gets complicated for an array that may number 100’s of LEDs.
The other is to simply string them together in series (a lot like Christmas lights) until the sum of the voltage drops of the LEDs equals 12 volts. That’s usually going to be 3-4 LEDs. Those strings will then be connected in parallel, as would normal light bulbs.
The problem is that if one of those 3-4 LEDs that are wired in series fails, you lose all of them (just like Christmas lights). If you have over 100 LEDs in a single light head, losing 3 or 4 not a big deal. But you can’t just replace those 3-4 in the field. Usually they will be “potted” (filled with epoxy) so you really can’t take them apart to fix them.
I have no idea what voltage is used in signalling, but with today’s solid state circuits, it doesn’t matter. The light head will likely be a self contained unit with two wires sticking out (or similar terminals), designed to operate at the specified voltage.