Anatomy of a Railroad Crossing

When a train approaches a railroad crossing, it triggers a signal to activate the lights and gates. Simple enough, huh? Not so fast. There’s a lot more to a railroad crossing than what you see as you’re passing by. There are a number of different technologies in play along the MetroRail line. And for those crossings that happen to be near busy intersections with traffic lights, Capital Metro has added or upgraded an additional technology known as signal preemption.

The Austin American-Statesman took a closer look at crossing signal technology. Check out the Statesman’s graphic which illustrates how the system works. Here’s the story:

This just in: Parking on tracks a bad idea

Capital Metro hopes ‘signal preemption’ technology will protect people who choose to do so anyway.

By Ben Wear

The intersections along Airport Boulevard, from 45th Street north to Denson Drive, present a confounding choice to drivers coming from the west.

Do you pull behind the cars stopped at the red light, hoping there’s enough room between the Capital Metro railroad track and the back bumper of the nearest car? Or do you play it safe and stop just short of the track’s signal arms, even if that means blocking another side street such as Clarkson Avenue? Or maybe you should stop even farther back.

Too often, cars make that first choice and then find themselves in harm’s way — and possibly afoul of state law. Now that Capital Metro has installed additional signal gate arms on the downstream side of the tracks and higher-speed passenger trains are set to begin service soon, the risk will increase of a car or truck being trapped on the tracks.

To address that, Capital Metro, working with the City of Austin and the Texas Department of Transportation, has added or upgraded so-called signal pre-emption technology at more than a dozen rail crossings for about $686,000. Capital Metro has had trouble debugging various aspects of its track control technology over the past few months, but when it works properly, approaching trains send signals that make traffic lights go green and close the gates sequentially to let cars clear the tracks and prevent more from taking their places.

This equipment wouldn’t be necessary, of course, if all drivers took the common-sense approach of never stopping their cars on railroad tracks or beneath raised railroad gates. Based on direct observation earlier this month, however, that is most assuredly not what is going on.

I spent two hours hanging out at 51st Street and 45th Street at the Capital Metro track, which in the case of 51st Street is just 60 feet from the Airport Boulevard curb line. I hid behind a huge metal control box near the tracks, obscuring me from the approaching cars. I wanted to catch them in the wild.

It took about 15 seconds for a car to stop on 51st with its tail end beneath the signal arm beyond the tracks. In two hours, about two dozen cars stopped under the crossing arms on 51st or 45th to wait for the light, and five cars parked on the tracks for periods lasting 10 to 30 seconds.

There were no close calls, however, when commuter trains came by four times on practice runs. Before going on, it’s important to point out that stopping where the cars did was probably against state law.

A section of the Texas Transportation Code deems it illegal to stop on a railroad track and, in a nearby passage, within 50 feet of a track unless the driver is unloading passengers or cargo. But the law, without listing a penalty for violations, also says that that passage doesn’t apply if the driver “is complying with … (an) official traffic-control device.”

Such as, presumably, a red light. However, it’s hardly worth pointing out that this defense will be hard to make in court by any driver hit by a speeding train. In short, parking on a track or under a signal arm is a low-percentage move.

Some people will do so anyway, however. So Capital Metro will have 14 intersections — out of about 70 along the 32-mile MetroRail line from Leander to downtown Austin — with signal pre-emption. Six are along Airport Boulevard, two are in Leander and the rest are in various places where a traffic light is relatively close to the track.

The agency already had signal pre-emption at some of these places to protect drivers from being hit by the daily handful of slower-moving freight trains that the agency has run on its tracks for years. With the commuter trains that run at speeds between 35 mph and 60 mph in mind, the agency had to move the triggering devices — called termination shunts — from about 800 feet before an intersection to about 4,700 feet back along Airport. In Leander, where the trains will be going at top speed, the trigger points will be 7,000 feet before the intersections.

Sometime soon (Capital Metro still can’t say when) the commuter train service will start for real. The signal pre-emption technology will almost certainly prevent any trains from slamming into cars at those 14 intersections.

Staying off the tracks and out from under those signal gates, however, is probably a better idea.

5 thoughts on “Anatomy of a Railroad Crossing

  1. Question about signal preemption….aren’t the Austin Fire Department and A/TC EMS already using signal preemption? What happens when an ambulance or a fire engine is screaming down Airport and the technology is greening all the lights at the same time that a train is chugging toward the same intersection and trying to green the lights in the crosstown directions?

  2. The problem. again, is that the intersections along Airport encourage bad behavior by motorists – if you don’t turn in and get in line, you won’t make the light, because somebody else will grab your spot. Motorists will eventually gamble and just get their spot in line – and sooner or later, one will get killed because of it.

    South Florida learned this the hard way – and on intersections much less dangerous than ours.

    Also, the 51st intersection is bad going westbound too – because of the left turns on to Clarkson (Red River).

    To inflict this on the public without re-engineering these intersection approaches at all is willful negligence.

  3. Adam

    Don, good question. Currently AFD and ATCEMS do not have signal preemption devices installed along Airport Blvd. However, if a Fire or EMS unit were preempting signals, that would not prevent the proper activation of the safety technology at a railroad crossing. (Thanks to AFD for your help with Don’s question.)

  4. Thanks Adam, your reply is reassuring. But make sure that as the technology becomes more ubiquitous, your engineers are prepared for device conflicts! It’s bound to happen some time, some place….which is okay as long as everyone knows how the device conflicts will be resolved.

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