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Comment by lynx23 | Hacker News Reader

I was very excited about EVs reducing the noise level in my city. Until I realized that most of the noise of a modern car actually comes from the tires. There sin't much difference between a modern non-EV car and an EV, sadly.

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At highway speeds there might not be much difference in noise levels, but there's a huge difference on city streets. In cities in with particularly noisy vehicles such as motorcycles, diesel buses, etc, electrification makes a huge difference.

With EVs slowly becoming more dominant in central London (most taxis, and many buses and delivery vans are electric now), I've several times had the slightly eerie (but happy) experience of being at busy intersections and noticing that it was unusually quiet. Then looking around and seeing that every vehicle waiting at the intersection was electric or plug-in hybrid.

> diesel buses

Ah, we love the electric ones here in sweden!

Of course they have to stop ~20 minutes to recharge instead of just turning back.

And of course when it's cold (which surprisingly does happen in sweden) the batteries can't hold enough charge to do 1 run, so they can't run.

> "Of course they have to stop ~20 minutes to recharge instead of just turning back."

London's electric buses (mostly UK-built bus bodies with BYD drivetrains and batteries) have large enough battery packs for them to run all day without charging. They get recharged overnight, when electricity is cheap, while parked in the bus depots.

As of March, London had 785 fully electric buses in service, out of a total fleet of about 9000. The fleet is planned to be fully electric by 2034, which could be brought forward subject to additional funding.

It will be interesting to see if they stick with the overnight-charging model or whether charging while in service will make sense on some routes.

London's hybrid buses are also pretty good for noise (not as good as electric, but a lot better than direct diesel propulsion). No loud bursts of noise when accelerating.

London's busses are very small.

Do you have a source that they run the entire day with no charging?

> "London's busses are very small"

Small?! The majority of London buses are double-deckers, around 11 meters in length with capacities up to 87 passengers (combined seating + standing). Perhaps not the world's largest buses, but I certainly wouldn't call them small!

> "Do you have a source that they run the entire day with no charging?"

Here's an old press release from when they were first introduced: "The buses are equipped with BYD-designed and built Iron-Phosphate batteries, delivering 345 kWh of power ... The batteries can power the bus for over 24 hours and up to 190 miles of typical urban driving on the service routes with a single daily recharging requiring only four hours."

https://en.byd.com/news/transport-for-london-launches-the-fi...

(The reality is that on many central London bus routes, there just isn't anywhere where they could stop for an extended period for recharging. But as more electric buses expand to suburban routes, maybe that will be less of an issue)

They are small. Most busses here have 2-3 segments.

The maker's estimation and the real life often differ quite much. Is there something about real times?

London can’t use multi-segment articulated buses (“bendy buses”) due to street size and layout constraints. Basically they’re too long to fit in many places they need to go. They did actually experiment with them on a few routes some years ago, but they were withdrawn after a year or two.

But that doesn’t make London buses small, because they’re double-deckers. Instead of increasing the length, they increase the height.

In any case, bus size is a red herring when it comes to electrification. A larger bus simply gives you more space to install larger batteries, provided you don’t exceed class/axle weight limits etc. Being longer and having more axles, an articulated bus should be even easier to electrify than a double decker!

London has been operating electric buses for almost 10 years now and has a fleet of nearly 800 units. If they weren’t performing to expectations, I’m sure we would have heard about it and they wouldn’t keep buying them!

Look, I've been to London and I've been to Sweden. Your busses are smaller.

Being double decker means nothing when almost nobody wants to bother to go up. But even then. They're still smaller.

> London has been operating electric buses for almost 10 years now and has a fleet of nearly 800 units. If they weren’t performing to expectations, I’m sure we would have heard about it and they wouldn’t keep buying them!

Yes, public administrations are known to run at maximum efficiency and never let any other considerations to decide what to buy.

Like here in sweden they're obviously corrupt when deciding what to buy for public transport.

If one bus means 10 cars and motorcycles stay off the road, the extra loud noise is probably worth it. IMO electric buses are a low priority task for most cities.

Really depends on the speeds. At slower speeds in residential areas the difference is noticeable, especially when cars stop and accelerate again. On larger faster roads not so much.

It's really noticeable near traffic lights. All that pollution and noise really is accentuated when the cars are accelerating away from the lights.

Indeed, the video says that: the tire noise for ICEs becomes louder than the engine at about 50 kmph. This means that for speeds slower than that, the more important component is the noise of the engine.

That's probably for a constant speed, though. ICE cars are loudest when they are accelerating. On many cars the engine is louder than the tires if you're floor the accelerator no matter what speed.

It depends a lot on weather and materials used to make roads.

If you're in the UK, most of the noise comes from "the kids" buying cheap compact cars (Fiat 500s seem popular) and modifying the exhaust to sound like a very, very poor man's Ferrari, or on Sundays, motorbikes.

That, and I've noticed that most diesel exhaust smell seems to come from a small number of vehicles: old VW TDIs, illegally modified taxis, and old buses.

IME you're right, but the cars we hear in a city are the outliers, not a nice modern quiet car. It definitely, in my experience, reduces overall noise to have a lot of electric vehicles.

I wonder if there are low noise tire tread designs? Of course there are probably trade offs. Snow tires are known to be louder than the tires you use in climates that don’t get snow.

Yes there are - new tyres are rated in the EU (and still used in the UK) for noise, as well as wet grip and fuel efficiency. [1]

[1] - https://www.kwik-fit.com/tyres/information/tyre-labelling

>Snow tires are known to be louder

Studded snow tires are louder than other tires, snow tires without studs are softer than normal tires so less noise. Modern snow tires without studs are surprisingly good on ice, which is the only place studded tires can compete.

Noise levels is one of the things tires are rated by, but a quiet tire would normally require a softer compound and softer compound wears out faster than harder tires

That's where a ton of the pollution comes from as well, the tires break down and fill the air with particulate. Road and brake particles as well

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