In New York City, congestion pricing leads to marked drop in pollution

It's true that brake dust is the primary PM2.5 emission from vehicles in an urban environment. However the PM2.5 component from tail pipes are still very significant, higher than the contribution from tires.

The order is:

1. brake dust 2. road dust 3. engine emissions 4. tire dust

https://www.sciencedirect.com/science/article/abs/pii/S00456...

https://electrek.co/2025/05/27/another-way-electric-cars-cle...

> though diesel engines spit out a bunch of bad stuff.

Exactly. The noxious tailpipe emissions in a city are usually from diesel trucks, small vehicles like motorcycles (small or absent catalytic converters), modified vehicles (catalytic converter removed or diesel reprogrammed to smoke), but not modern gasoline ICE vehicles.

The love for diesel engines in many European countries was always confusing to me.

PM2.5 is also a broad category of particulates that come from many sources. The PM2.5 levels in the air depend on many sources, with wind being a major factor in changing PM2.5 levels. It’s hard to draw conclusions when a number depends on the weather and a lot of other inputs.

"relatively clean" means 85% of PM2.5 is from non-exhaust sources, and 15% is from exhaust after catalytic conversion. In New York EV and ICE are pretty much on par when it comes to this category of pollution, as the additional weight increases non exhaust sources. Source: https://www.sciencedirect.com/science/article/abs/pii/S13522...

It is different in Africa, where catalytic converters are harvested for precious metals and cars are driven without them.

Is that true for slower moving vehicles? I can't imagine there's a lot of brake dust generated by stopping & starting in the 0-10 mph range.

How do EVs fare in this regard? Brakes are used significantly less, but the additional weight from the batteries chews through tires faster.

It always surprises me when people want stop signs in their neighborhood for traffic calming. The last thing I want is all of the noise and pollution of vehicles stopping and starting over and over again; surely various piece of road furniture like bulb-outs, roundabouts, etc, do a better job with fewer drawbacks. Other than cost, of course.

There are some early tyre and brake dust collection systems which might help, but that won't do much for the road dust.

I've been wondering whether, theoretically, if self driving cars become widely usable and deployed in cities, will they be able to safely operate with harder tyre compounds and harder road surfaces that shed less but don't grip as well?

If nothing else, less aggressive driving should lead to less shedding.

There’s also ammonia from farmland, it reacts to form secondary PM25

It’s a national issue because as soon as one city tries it out and it turns out to be pretty good and none of the doom scenarios ensue, congestion-charge opponents all over America lose most of their talking points.

Best they can do now is, “Well, we’re not New York.”

Attention economy, the algorithm, rage-bait, maximizing engagement, doomscrolling - pick your buzzword. Individual people care about all sorts of weird things, but on average, this and no other reason is why a person in Idaho suddenly finds themselves caring about Manhattan congestion pricing. It's easy to point a finger and laugh/marvel when it's something so obviously absurd to you, but of course you and I both have entirely different blind spots where our attention is marshalled and our opinion is formed by the rage-bait engine. Ours must seem preposterous to those on the outside looking in, too.

Probably very clear-cut, right? "No parking, no business" never made sense, but it makes even less sense in a city where cars are involved in less than a third of all trips

Especially considering that

* Congestion is an opportunity cost in itself already, which is paid in wasted time by all road users, impacting mostly those who spend a long time on the road, which is busses, taxis, professionals and delivery drivers, as they spend the most amount of time actually driving in congested roads

* Congestion pricing forces trips to self-select on cost/benefits in actual dollars, instead of time, so you optimize for wealthier trip takers, short stays or high value trips, where before you would favor long stays (which make looking for parking forever not so bad), and people who don't value their time very much

* Car use remains heavily subsidized, as motorists do not come close to paying the full costs associated with their road usage

> The strength of conviction people have about this policy–almost either way, but certainly among those against–seems to scale with distance from the city.

Writing this from mid-town Manhattan. There are a lot of strong feelings about congestion pricing. It was a common topic in the local media. The stronger voices tend to be those who drive and are affected by it. For Manhattan that is a relatively low percent of the population.

There are some people who are pro-congestion pricing, but as often has with these things the benefits are distributed whereas the costs are concentrated, leading to certain behavior.

Feels like this is the curse of modern US politics. I'm convinced the majority of people that "want high speed rail in CA" don't live in CA. Further away they live, the stronger they will argue for why we should have it.

It's because everything is a culture war issue now, and anything remotely seen as helpful or benefitting society or taking even an inch from cars is "bad" for the people who live in places like Idaho (and Staten Island).

Fox news.

Cars are en extension of some Americans' identity and driving is something they feel utterly entitled to.

I've lived all over the world and in NYC for decades so it seems silly to me. Bust most Americans have never seen or ridden an effective form of public transport. So they view congestion pricing as an infringement on their rights and quality of life.

https://pmc.ncbi.nlm.nih.gov/articles/PMC7314691/figure/f002...

Take a look at their figure, especially in May 2020—the average appears lower, but, more significantly, there is much less variability in May 2020 compared to earlier years.

The authors' model quite strongly includes their preferred confound (secular decrease in PM2.5) but doesn't explore what other covariates could explain the differences between years.

It's fine to say that one should be skeptical, but one contrary report doesn't invalidate an antecedent report, and the structure of a linear model strongly influences an outcome.

"Not statistically significant" doesn't mean did not happen.

Given the physical mechanisms involved it is implausible that pollution did not decline. And if you look at their data you see a marked drop in 2020 at day 70

This is March 10 or thereabouts, I think. And there are ZERO high pm 2.5 days for a 20 day stretch or so. This isn't seen in other years. The vast bulk of days are below the trend.

And then for the rest of the year there are some days above the trend line but no high pm 2.5 days.

This fits with people being extra cautious in the early days and then relaxing a bit as things went on.

Now, I'm eyeballing this so I could be incorrect. But:

1. The effect was found in other cities

2. The physical mechanism makes it highly expected that there would be a drop

The study was about the slope of the regression modal, but if you had scrambled the years I'm fairly confident I could have picked 2020 out of the set.

That's a very surprising finding since the drop in traffic was very noticeable. I wonder where the PM2.5 is coming from?

We have fruit trees in our backyard. The year of the COVID lockdown they had so much fruit the branches broke from the weight. Most fruit I've seen in 20 years in the house, by a large margin.

There's a large (long time) movement to do this to lower Manhattan, the most public transit connected area in the US (probably North America, definitely up there in the world). It's getting pick up again.

This is already underway

Big agree. Times Square would be a great place to start.

> You could, at the extreme, ban all motor vehicles but the opportunity cost would outweigh the benefits

We did this in Times Square and on Broadway, and it's honestly been great. I say this as someone who takes cars far more frequently than most New Yorkers and has a place I lived at full time for over a decade off one of those closed-off sections of Broadway.

The point of congestion pricing is to let market mechanisms determine where the optimum is.

I wouldn't assume your last claim.

It could also be the case that making it viable to drive personal vehicles at all inside a dense city comes with opportunity costs (parking, roads that cut through infrastructure, pollution, noise) that aren't worth it.

And I'd wager that it is the case.

Since this is generating revenue for NYC, you can't consider whether this tax is good or bad in a vacuum though. The alternatives are a different tax with its own effects, or more debt, or less spending. (In this case, the revenue goes to the MTA.) Any opportunity costs due to less traffic are at least partially offset by opportunity costs you aren't having to pay somewhere else.

Dynamic pricing based on congestion would solve this. It would also almost certainly result in higher costs for drivers though.

Try things and ask the people in a year if they like the results, then do the good ones more and the bad ones less.

You take a walk along a 55-mph stretch of highway, and then you take a walk down Broadway, and you see which one makes you feel better as a human being.

21 minutes faster.

https://www.tomtom.com/newsroom/explainers-and-insights/the-...

The city does it for the benefit of the public, the Corp does it for the benefit of the shareholders