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Comment by jeffbee | Hacker News Reader

It's hilarious but sad to watch Americans learn things that agencies abroad already know. The other example of this I saw today was that in NYC the congestion pricing has "surprisingly" slashed the number of car crashes and injuries in Manhattan. Like, duh.

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I feel this is positive news moving in a positive direction. Do you suggest not doing anything to improve the situation? We can’t go back in time. But we can help ourselves in the future.

I feel this improvement is negligible. I doubt you'll see any meaningful change in your lifetime.

At best you'll see an electric car renaissance. But the infra for trains and public transit? Doubtful.

It’s still a positive change an I’m all for it.

I'm all for positive change too. But as someone who isn't delusional, I have to account for practicality rather then dreaming about an unrealistic future.

I think it’s more that Americans seem to be surprised by things that people in other countries have known for decades.

Meanwhile, the current administration is trying to send us back to the 19th century in civil rights, healthcare and energy policy.

https://xkcd.com/1053/ but with different numbers

Of course its positive news. Of fourse we cant go back in time. Its still good fun to poke at US for being so late on these discoveries.

One way to help yourselves in the future would be to learn the meta-lesson that actually things that work in other countries mostly work the same way in the US too.

Oh, we all know. It’s just convenient to pretend otherwise sometimes.

Some people take your word for it, but some people just have to touch the stove to learn that it is hot.

The US has been pressing its palm against the grill for a while now.

Yes this whole thread is so depressing. Most commenters here are talking as if electric trains were an oddity. It's like listening to people questioning the benefit of running water over the old school walk to the well.

How do you get the choir to sing? You preach to the choir.

When the needle is moving in the right direction, publicize that so everyone knows about it. That public info makes it harder if someone then comes around and suggests undoing/defunding or any other type of thing that stop the needle or make the needle move in the opposite direction. Keeping the info quiet makes yanking the plug very easy

I dunno...

Many trains in London still don't do regenerative braking despite the technology to generate electricity from motion being around for... checks notes... 194 years!

You probably know more about this than me, but it looks like some lines do: https://tfl.gov.uk/corporate/transparency/freedom-of-informa...

Regenerative braking in cars also keeps a lot of brake dust out of the air. A pair of brake pads lasts about as long as the life of an EV.

> You probably know more about this than me, but it looks like some lines do

I'm confused. Your phrasing suggests that you're adding in new and potentially conflicting information, but "many don't" and "some do" mean the same thing.

The missing piece of info here is that while most of the trains have the capability to do regen braking, it is generally ineffective because it can only be used if another train on the same section of track happens to also be accelerating at the same time.

That happens rarely enough that most of the trains, most of the time, do not effectively regen, and instead use mechanical or resistive braking.

There was chatter 20-30 years ago about using flywheels to bank the energy until needed.

Do trains need batteries for regenerative braking, or is it sent right back on the same power lines?

The article says this version sends it back out on the same power lines, either used by other trains or pushed back into the grid. Seems like a perfect job for supercapacitors, although I have no idea about the feasibility of that solution. I imagine that batteries having huge input/output cycles like that wouldn't be healthy for them. Again, pulled from my imagination because I don't really know much about battery wear/use.

If it were 1995, the optimal solution would have been NiMH batteries at the side of the track. They can do massive currents in and out, and a few tons of batteries would be enough to fully store the energy of a passenger train stopping from 60 mph to nil inside 30 secs.

NiMH could have been attached directly to the rails.

Today, lithium batteries win for Watts per dollar, and perhaps custom made packs could also be attached directly to the rails.

But a cheaper solution is probably bidirectional inverters, allowing the DC generated by the trains to be fed back into the 3 phase national grid.

Unfortunately, all trains in London today cannot regen into the grid - they can only regen into the rails and hope that some other train on the same rail is accelerating at the same time to use the energy. By my estimates, that only happens less than half the time.

Generally, trains are scheduled so that one train decelerating roughly coincide with another accelerating. You can plan ahead and orchestrate all you want and overcommit capacity as much as you want. Leftover that didn't cancel out is fed back to hydroelectric dams for gravity storage which do require cleaning but are immune to chemical degradation.

By the way, implementing regen on synchronous motors is relatively easy, IIUC, command a positive torque to the inverter and it draws current and line voltage gets pulled down. Command negative and opposite happens.

The deepest metro lines are also boiling, because the heat from braking just gets constantly absorbed into the ground, and the ground's ability to disperse the heat is maxed out.

Some of that heat is now used to heat homes via a local heat network originally built to use combined heat and power.

> The other example of this I saw today was that in NYC the congestion pricing has "surprisingly" slashed the number of car crashes and injuries in Manhattan. Like, duh.

You didn't see the online crowds screaming up and down that it wouldn't do anything but pick the pockets of people? Many genuinely did not believe things would change.

I don't see why it couldn't be surprising - if there are fewer cars in Manhattan, it could mean the cars will have a higher average speed, meaning they might be more likely to get into an accident.

My experience in Manhattan is that when it gets really congested, it turns into a giant game of chicken with everyone jockeying for position. This has got to lead to a lot of accidents (although probably mostly fairly minor)

"Surprisingly" is an opinion on the part of whoever wrote that, but it's not a surprise to any of the advocates.

It has been working better than expected, possibly because the bad drivers were breaking a lot of other traffic laws and this one's easier to enforce so is actually keeping them away.

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