He must know that his outside lights are burning bright, that the water in the boiler is sufficient, that the air-brakes are in perfect working. He must from moment to moment glance at the hands of his watch, and must know exactly where he is upon the road. And yet all the while his eyes must hardly be taken from the darkness into which his engine rushes, to catch the first glimmer of the signal which is his guide.
Since the safety of many lives thus depends upon these signal lights and upon their sudden clearness to a mind that must attend to many things at once, the symbols should at all times be the least ambiguous that can be planned. Yet the present night-signals, given by colored lights beside the track—upon many roads, white for "safety," red for "danger," and green for "proceed with caution"—are open to grave objections. For the human eye at its best and without abnormality is liable to mistake the signal hues at night, especially when the outward conditions are anywise untoward, whether by the distance or the low-burning of the lamp, or by fog or smoke or storm. And even when the colors are perceived with perfect accuracy, the use of the common oil-light called "white," as one of the signal colors, throws a dangerous task upon the engineer, inasmuch as it requires him to take constant heed lest he regard some window-lamp, or other meaningless light along his course, as a sign that all is well, and in consequence rush onward to his train's destruction.
That objections of this character are supported by strong evidence, and are not of merely theoretical importance, but are connected with actual and known disasters—to make this clearer is one of the main purposes of the present paper.
In regard to the use of white as part of the signal code at night, the danger from this source has long been recognized by leading signal engineers, although in spite of this recognition its use continues on a large number of our American roads. It is not many years ago that an accident occurred at Whittenton Junction, Massachusetts, from this very cause. The engineer mistook a lantern hanging from the gate at a street-crossing for his safety signal, and crashed into another train. More recently, Mr. Baggett, of the Galveston, Harrisburg and San Antonio road, has given an instance where disaster resulted from the use of white. The railway signal, in this case, was exactly in line with a light shining from a high bay-window; and when the signal light itself one night was out, the engineer mistook the light in the window for his signal, and a serious accident was the outcome. And other cases are reported by the Interstate Commerce Commission. A switch light happened one night to be extinguished, and the engineman "failed to notice the absence of the light, being deceived, he says, by lights in the vicinity"—a deception which brought damage amounting