Sunday, November 10, 2013

Indian Road and Railway Signals

I derive great pleasure in using cheap tricks to fool my friends, all because I had been the victim a countless times at the hands of my friends. No malice anywhere and at the end of it all, there may even be a small lesson in it.
I used to tell a small story, as a prelude to a crucial question. Two gentlemen, one English and the other Scot, went into a café and ordered coffee. They were served two pots of black coffee, two cups and saucers, two spoons, a small dish of cubes of sugar and a small pot of cream. The gentlemen made coffee, each for himself; they are English and Scot, remember. Then, the English started stirring his coffee with a spoon clockwise. Simultaneously, the Scot did the same, but counter-clockwise.
I asked, “Why?”
The inevitable response has been, “What the English do, the Scots cannot bear and vice versa.”
“But,” I continued, “I did not ask why they stirred clockwise and counterclockwise. My question was why they stirred the coffee. The clear answer is simple: to dissolve the sugar! Ha, ha …”
Cheap, yet it brought out how in a conversation we add context to suit our tastes and not very objective ones at that.
Now, to the meat of the current post. I have travelled on Indian railways extensively and on Indian urban roads too. I have seen traffic signals along both modes of transport. The pictures below will give you the context.

Please look at the pictures carefully.
Now, I can ask the crucial question: “Why signals?” So, you are ready with the right answer: “To control traffic!”
But, I am going to tell you that you are wrong, in a particular sense. What sense is that? It is one of contextualizing, again. I had shown you the traffic signal images immediately after telling you about the story in the café. So, you assumed this was a trick in the same mold. But, that would not have suited your intelligence as I had assessed. Here, the question, “Why signals?” implies, “Why the difference in signals?”
“Where is the difference?”
Look carefully at the images again. In the road signals, the red is at the top and in the rail signals it is at the bottom. If you start to shake your head because in the semaphore (MAUQ) signals, the filters align from top to bottom as Red, Amber and then Green, I request you to recognize that the thing plays out relatively. In the semaphore signal, the light position is fixed and the filters move up and down, whereas in the modern signals, it is the other way. Hence the reverse order. In rail signals it is green at the top and red at the bottom. (Those of my vintage would counter that in earlier times, the arm used to drop down instead of going right up to give the green signal, making the above logic invalid. Not so. One has to merely shift the frames of reference to see the underlying constancy.)
I had asked this question, why the difference between the order of lights between the road and rail signals, to many people, both layman and rail experts. I have not received any illuminating response except that it has always been so in the railway sector. My curiosity was not assuaged. I started to think for myself, a dangerous mission.
I know why the red signal is at the top in road signals, at least one of the reasons. It lets you see over the top of the vehicle ahead of you. No driver on the road can deny that he or she had jumped a red light, if only because he or she was following the vehicle ahead blindly, metaphorically speaking. Well, having the red on top helps moderate that wrong tendency. Along railway lines, this does not matter. Indeed, as I see it, the red light is pretty much level with the driver’s eyes.
But, that is a low level instrumental aspect of this issue. There must be something more, I told myself. In road traffic, as I understand it, the default mode is to “Go”, to be stopped by a red signal or a stop sign; otherwise, you are free to move. This is the only way one can understand flashing yellow lights or “Yield” signboards that control your movements. When you are stopping on a road, it is recommended that you use your blinking lights to warn others that you have stopped. No warning if you are moving.
In rail travel, the train can move only on the explicit permission to go, or proceed with caution, till the next block. The stopping distance for trains is in tens of multiples of that for an automobile.  This is why the “Pull chain to stop train” message is an emergency measure. The driver is under the control of the signals, if given the permission to go, the train has to go. That is, the default position of the train is “Stop”.
This basic difference manifests itself in the difference in the order, top to bottom, of signals.
I strongly believe in the basis of my analysis here. It is for others who know things are not this way, that the differences are the result of some other aspects of the differences between road and rail travel, are welcome to enlighten me.
It is curiosity that gets people to understand and apply the context. When you answered the signal question almost unthinkingly, you failed in contextualization, just as in the café instance
Raghuram Ekambaram

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