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NTSB says signal brightness caused UP crash
Are the requirements for signal brightness expressed as lumens and angular field of view? If not, why not. To express brightness in terms of watts of power should never have been applicable.
Fortunately no one died or was seriously injured in this accident, but it is surprising that this type of accident has never happened before. I am surprised that no one in the signals department foresaw the possibility of signal masking of incandescent signals by the much brighter LED signals.
I noticed immediately when they first came into use that green LED highway traffic signals can be uncomfortably bright–they are meant just to be visible, not to illuminate an area–so it is not surprising that they outshine incandescent signal lamps when the two types are used in close proximity in railroading. In line with Gerhard’s comments, the LEDs would use even less power if their apparent brightness were scaled back to match that of the incandescents they replace.
An interesting but unfortunate case of the visual “read through” phenomenon - seeing the signal beyond while ignoring the nearer one. This can happen to auto drivers, too, where stop lights are closely spaced.
Back when incandescent lamps were the only type of lamps used in signals, there was no thought of any lamp that used less power to give the same level of illumination. How did people buy bulbs before fluorescent lamps were devised? by the power (watts) consumed.
When buying CFL or LED replacements for incandescent bulbs, we should look carefully to see what we need to buy to give the same–or higher-level of illumination.
It would be well if the regulations concerning illumination in signals were rewritten to state the amount of light that is produced so that such a situation would be avoided in the future.
Why can’t all signals be replicated on a control board in the cab? This would appear to prevent these type viewing errors.
Jesse Harrup: because it would cost MONEY.
LED signals are too bright if a signal gives a false green instead of a true RED it could cause a derailment.