The platform edge lights found on the Metrorail system are a wonderful amenity—and I’m sure that when the system was newer, they seemed incredibly futuristic compared to (for example) the New York City subway. But in 2011, can we do better? Imagine if each platform edge light were replaced with a grid of RGB LEDs, hooked up to a microcontroller (it wouldn’t need to be anything terribly high-powered; a PIC would do just fine). All of the platform edge lights along one platform could be linked together with a 1-Wire bus and thence to the station’s RTU, or perhaps directly to MetroNet through a microcontroller with an Ethernet interface on one side and a 1-Wire interface on the other.
What could these new platform edge lights do? Aside from the obvious—using the RGB LEDs to show the line color of an arriving train—they could also warn passengers at the rear of the platform when they need to move up to catch a 6-car train. The Metrorail system will continue to run 6-car trains (at least off-peak) for the indefinite future. Even though the 7000 Series cars can only be run in sets of 4 or 8, the remainder of the Metrorail rolling stock is in married pairs, making 6-car trains a common occurrence. With all trains stopping at the head of the platform, passengers towards the rear are often caught off-guard by 6-car trains.
If 6-car trains ever return to making stops at the center or rear of some stations (as they once did), the same method could be used (with arrows going in the opposite direction) to show passengers when they need to move down along the platform towards the head of the train.
Improved platform edge lights could also display the ISO-standard prohibition sign to show that an arriving train is not in service. Of course, all of this information is displayed on the PIDS currently, but let’s face it: the PIDS aren’t perfect. More often than not, the displays aren’t visible from the extremities of the platform. And even though the PIDS do show train length, most people don’t really know just how much space along the platform a 6-car train occupies—that is to say, even though the PIDS may show that a 6-car train is arriving, that doesn’t actually tell people where to stand to catch the train.
When the platform itself is not in service (as is the case when trains are single-tracking at a station), the prohibition sign can be combined with an arrow to direct passengers to the opposite platform. This solves what seems to be a rather common problem—passengers rarely seem to know where to wait for a train when they’re single-tracking.
Would these new platform edge lights be expensive? Yes, but having them fabricated in bulk should help to keep the cost down (particularly since electronic parts like PCBs and LEDs and microcontrollers are often far cheaper in bulk). In addition, I believe there’s an important principle here: if we desire to continue to refer to the Metrorail system as “America’s Metro” and hold it up as an example for the rest of the country to follow, then we had ought pursue technological innovations which further improve the usability of the transit system. Quite honestly, a flashing red light just isn’t the forefront of technological innovation anymore.