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Comment by de_watcher | Hacker News Reader

The hell? Just put big automatic gates everywhere. Seems like a simple life/cost estimation exercise.

Actually no. Cannot be too big and automatic. You need to allow a stranded car to break free. You must not crush a car that is only half way in.

Sigh.

Railway crossings are pure evil. There is no fail safe design that I know of without adding a proximity sensor inside the car (I am a railway signalling engineer). Would love to be wrong though.

I know that at least in this area some wyes and crossing points use radar (the same type used for lane occupancy on roads) as an additional safety measure---something like track circuit clear but radar detection of an object results in a very restrictive signal like a "red-yellow." Do you know if there's a reason why this hasn't been deployed for road crossings? Definitely it wouldn't be perfect but seems like it could help with stuck-vehicle scenarios, especially in more urban areas where speeds are low but visibility is poor. I guess I assume that the reason it isn't being done is because it would require some kind of upgraded cab signalling that would cost too much to roll out.

Googling "MCB-OD crossings" will bring up various pages and videos that show such crossings in the UK. They are relatively new to the UK but I believe they have been used for some time in continental Europe.

They have disadvantages including expense, and additional road closure times (compared to automatic half-barriers) as they must be closed and proven clear early enough that an approaching train does not need to slow down.

Trains are very heavy and have long braking distances at speed, in some cases over a mile. For a train to have enough time to stop, the crossing would have to be kept clear for a very long time, which would probably tempt drivers to bypass the gates since they would perceive the crossing to be overly safe (described in the article as the "cry wolf" phenomenon).

In the UK many crossings have full width barriers, and must be confirmed to be clear of road traffic after the barriers have closed before the protecting signal can be cleared for a train. These are effectively fail safe.

Confirmation comes from observation by a signaller or crossing operator either directly or by CCTV, or automatically by LiDAR and radar. These crossings tend to be used in areas of heavy road, pedestrian or rail movements, and when train speeds may exceed (from memory) 100 mph / 160 km/h.

Their disadvantage is additional installation, maintenance and operational costs. They must also be closed for longer before a train arrives than an automatic half-barrier crossing to allow for the required safety checks and ensure that signals are cleared far enough along the line that approaching trains do not need to slow down.

Think about the thing you know best. Imagine an article about a challenging problem related to that thing. A person with almost no knowledge of that thing reads it and says, “Seems simple enough” and presents a solution. Are they likely to have overlooked something? Misunderstood the problem? Be unaware of the challenges in solving it?

By my interpretation of the article, it seems to agree that this is the solution. The caveats seem to come mostly from paying for it.

Yes, but sometimes just bluntly stating a solution can be a request for enlightenment.

Can we just put this comment on the top of every discussion here?

"Why don't they just ..." https://blog.jgc.org/2012/08/why-dont-they-just.html?m=1

> Seems like a simple life/cost estimation exercise.

All safety mechanisms are this. The tricky bit is the value of life calculus. Is it worth an added $10/year tax for every taxpayer to MAYBE save 1 life per 5 years? You'll get different responses for different reasons.

That $10 may be a rounding error for many, but to some its the difference of a week of lunches for their kid or not, and they vote, too.

Just for completeness $10/year from every taxpayer is $1.43B/year from one billionaire. So the problem of $10 being unaffordable to some is easily handled.

Asking someone else to pay is always easy for those not being asked, sure.

I wonder if that's the most cost-effective way to use $1.43B to save lives?

With trains the cost/benefit is greater than just stopping the crash from taking a life. Train/car collisions are messy and require fixing the infrastructure that has been disrupted (a collision/derailment will most likely screw up the tracks and any equipment in the way); and the train line will be out of service for the better part of a day, at least.

Read Darwin Awards. You find even with the gates in place people get out of the cars to raise the gates and still try beating the trains.

I was once closed in by automatic beams here in NL. Not a fun experience having to lift my bike through some hedge to get out.

This is probably better than nothing, but it is amazing how often cars get stuck in them.

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