They already have multiple systems that do proximity warning plus manned crews.

Lots of things beeping and going off just results in them been ignored, this had happened on flight decks and hospitals.

Semi-autonmous collision avoidance that's on by default however could be an interesting idea.

To err is human, to really fuck up requires a computer - as one of my professors used to say.

LiDAR only really works in good meteorological conditions, which is frankly when you need it the least.

As cars have repeatedly demonstrated, LiDAR doesn't work well when there's water droplets in the air such as rain, snow, fog, or sea spray.

Momentum on a 8000 ton ship is a hell of a thing. By the time collision alarms are in play, you're already screwed.

I would argue that the range of the collision alarm should take the ship's mass into account. Certainly my minivan's does. Have softer threshold alarms that sound earlier. Yes, even if it causes some false indications it might be a net improvement (though they should be cautious in making this kind of design change because it might not be a net improvement).

Active detection measures like radar and sonar are out, because they give the ship's position and capabilities.

Your minivan doesn't have these concerns.

I honestly thing they should be “giving away their position”. Pretending they shouldn’t is simply ego, and demonstrably dangerous.

It’s perfectly normal to see this in our own waters. AIS will identify the vessel as being named simply “Warship” or “Surfaced Submarine” (where “Warship” means “none of your business”, and “Surfaced Submarine” should be treated as a hazard to be actively avoided, as they're damned difficult to spot). They usually won’t give any useful to/from port (part of the AIS messages), and I’m not convinced their MMSI (identifying number) is actually fixed, but more likely disposable (or in practice, simply ‘0’).

And that’s okay. We can work with that. I don’t actually need to know who they are, I just need a location, course and speed so my radio can calculate whether our closest point (CPA) is uncomfortable, and the designation of “Warship” is perfectly sufficient to ensure my eyeballs and the computer are talking about the same vessel. MMSI should be useful, but rarely is - Warships are surprisingly difficult to raise on civilian radio. It's not unusual for them to have no idea how the civil band is channelized. In & around ports if you need to communicate with them, it's best to look for their police escort & raise them, and anywhere else .. "If it's grey, stay away".

There’s entire oceans for them to go play hide’n’seek in. I don’t think it’s too much to ask that when they’re in a shipping lane, they obey the rules of the road - in peacetime at least. If they want to be invisible, perhaps the worlds busiest shipping lanes aren't the best hiding places.

Or, look at it this way. If a small sailboat was arsing around in one of the world’s busiest shipping lanes, at night, with no navigation lights, no AIS, no radar reflector, and what appears to be insufficient watch-keeping/lookout - and got mown down by a frieghter - you’d have very little sympathy. “That’s a terrible shame, but realistically inevitable”.

This is exactly what the USN look like to everyone else on the shipping lane. Playing hide’n’seek on a busy road, and wondering how these accidents keep happening. And yes, they should be blamed for any incident where the bare minimum of good behaviour would have averted entirely. (I should say seamanship, but this concept is long since lost on the USN)

They can just be for peace time situations like the past two collisions with container ships

I'd think that they'd already have radar systems that can track every ship in a 50-mile radius.

Using radar gives away your position and radar capabilities. For this reason, most active navigation measures are (almost) never used on naval ships.

My understanding[0] is that use of radar to provide continuous situational awareness is routine, not avoided in the way you describe.

[0] confirmed by this piece by a recent US destroyer commander: https://warontherocks.com/2017/06/how-could-this-happen-the-...

And colliding with a tanker and being in the media for several days doesn't reveal your position?

I really get your point about stealth and would agree that it would make sense not to use radar. On the other hand, if you can't avoid collisions (for whatever reasons) your position will be known very quickly anyway.

Good point. Does this apply even in peacetime while in friendly waters? I suppose you never know when you might become a target.

Peace can turn into war very quickly indeed, so my understanding is that the Navy prefers to err on the side of caution.

Please tell me how a radar switched to off would give away the position of the ship in a war time situation.

You're sailing through the Strait of Hormuz, one of the busiest shipping channels in the world. There isn't a shooting war underway, but you are within range of Iranian cruise missiles and naval craft.

It's not exactly war, but it isn't exactly peace. Do you see what I'm driving at?

Huh? They're explaining why they wouldn't switch the radar on.