Or even just walk.

I mean if cities were more walkable there'd be less need to join the arms race of more and more aggressive cars on the road.

I mean... walking is clearly not a vehicle. It is an important part of sustainable and pleasant city planning, though!

The word "cars" appears exactly once in the whole dashboard, so I would assume it covers consumer vehicles, not cars.

why? Assuming that all vehicles are zero emission vehicle, why should we reduce the numbers of cars from the streets?

Here are a few reasons:

Cars still pollute - dust from tires causes harm to lungs and streams and is contributing to the decline of salmon populations.

Cars are heavy, damaging roads, increasing maintenance costs compared to electric bikes or public transit.

Cars are large, and need to be parked. That means larger roads and more parking lots, rather than using the space for housing, businesses, or parks. Bikes, buses, and trains don't have the same problem.

Cars reduce access to cities - highways and arterials are difficult to cross, and divide neighborhood activities.

Cars are dangerous, humans are generally only moderately adept at driving them. We have tons of injuries and deaths because people are bad at driving. (Or have to drive when they shouldn't.)

Cars are inefficient. The energy used to move 1 person via a car compared to any other form of transport is one to two orders of magnitude higher.

Cars require distributed energy rather than the centralized infrastructure that public transit requires, which means many small chargers rather than one electrified rail.

Cars aren't affordable for everyone, leading to inequalities in who is eligible to work at certain jobs.

There are probably more reasons, but cars are a deeply inefficient and costly means of transport.

More reasons:

It makes the world uglier, noisier, and homogenized.

It makes urban regions hostile to families with children.

It creates a constant feeling of stress and aggression (road rage)

It requires a surveillance state, a police state, and thousands of laws that all must be followed precisely to uphold. And this takes away justice system resources that could be used for other things.

The roads must constantly be under construction, adding annoyance and expense for everyone.

Congestion wastes innumerable hours of our lives.

Not great with kids because car seats are expensive, annoying to install, and keeps you more tied to one vehicle because ridesharing and rentals don't always have them.

They are an attractive target for thieves because they are among the single most expensive things people own and you can use the loot itself to escape.

It comes with an endless barrage of annoyances for the drivers: parking fees, tolls, insurance, tickets, license renewals, city stickers, emissions tests, maintenance, car washes, refueling, getting towed, getting booted, etc.

Drivers kill over 40,000 people a year in the US, and over a million people a year around the globe. Drivers are the leading cause of dead kids in many places, and places built for driving are extremely unpleasant for walking, biking, chatting, etc. They also are very expensive to provide services to and maintain.

Because cars have negative externalities other than carbon emissions.

Keeping the number of cars on the road flat would be a huge achievement. The fact is that cars provide a huge amount of utility which is hard to give up unless you live in a dense city with good public transport provisions.

Carcentric city planning and good public transport are pretty much mutually exclusive.

Not necessarily, but that's how the anti-car crowd wants to frame the discussion, which is why it's not going to get anywhere.

If you want to increase non-car infrastructure, you need to convince people it's in their best interest, not attempt to punish them for owning a car. People would love to have an fast, safe, and convenient system for getting around, and right now, that's a car. Most anti-car discussions talk about punishing people for having a car without trying to replace it with something sensible that is fast, safe, and convenient. Of course there's push back.

If you want to increase non-car infrastructure you either have the problem that you have room, but density is insufficient (e.g. suburbia, cities with too many huge parking lots), or that there is no room (e.g. reasonably dense metro areas). In either case you need to fundamentally restructure the infrastructure to make public transport attractive. That's not really possible without making life worse for drivers.

Again, that's where you lose the discussion. You think motorists love huge parking lots or wide roads. They don't. They couldn't care less - they just want sufficient parking and sufficient travel lanes to get around. If there's one fast lane with less traffic, they'll be happier than 5 lanes of slow traffic. They don't want congestion, and are willing to support initiatives that reduce congestion. Right now, the only consistent initiative is either painting bike lanes in the middle of no where that no one will use or adding more car lanes.

But the frame of the discussion right now is to punish motorists for being motorists - they don't have a choice. They can't afford to live closer (or there's no options that give what they are looking for), and there's no safe, fast, or convenient way to any place they need to go without a car.

Give them a safe, fast, and convenient way from suburbia to downtown, and they'll support reducing highways into half their size. Right now, the discussion is "suburbia bad, car bad, you bad - be better"

Now please suggest how you want to provide fast convenient car travel without wide roads and lots of parking. I'm all ears for clever plans that can replace five lanes of slow traffic with one lane of fast traffic. The only one I can think of is to cut the number of cars by at least 80%, probably more.

One thing I haven't seem explored much is having car-carrying trains. Load your car onto a train, get to downtown fast without traffic jams, drop off the car in an adjacent parking lot once you're in the city. Walk around a mostly car-free city, then take the car-train back to suburbia where you can drive the last 5 miles back to your house and park overnight.

That sounds like a small improvement over Park and Ride schemes that already exist.

Yes. A goal is to reduce the number of cars & to optimize the space used for other modes of transportation. However, to achieve that goal, you need wide & motivated political support. You want people to support your goal in the way MAGA crowds line up for hours to cheer for Trump - otherwise, you're not going to get it done.

You don't achieve that by talking down to them, treating their choices with disdain, or telling them that they expect to much. You do that by giving them a vision they want to fight for & a path to fight for it. A vision, for example, where you don't need to drive, but you could drive - and that driving experience will be even better than today. A vision that you wouldn't want to drive, even though the driving experience is even better than today, because the alternative is even better than an improved driving experience. That's how you achieve support.

If you tell them they should stop using cars, they're going to ignore you, because there's no better alternative or even remotely equivalent alternative. If you actually try implementing it without making a better alternative, they're going to resent you and your goal.

I think what you are saying is you can't make public transport more appealing just by making the alternatives worse.

Yes, that's definitely what I am saying.

You need to tell them that you'll take away space from cars in the dense area of the city and make the suburbs denser. Otherwise you wouldn't be telling the truth. Neither statement is popular.

But a car is only fast, safe, and convenient if a relative minority of people use them. Once they become the default, cars are terrible.

Even in a metro area with nothing but cars (& a token bus system), it's still the fastest, safest, and most convenient method of transportation, because there is no real alternative.

If you attack the fastest, safest, and most convenient method without providing an alternative that is even better, you will face resentment. If you can provide an alternative that is even better while making driving better too, you'll probably get enough real support to make it reality.

The things making walking, transit, etc. Better are usually the things that make driving worse.

for example?

For example they need a lot of nonrenewable resources to build.

trains much more and bikes (not a lot in comparison with a car), but still, too.

Trains transport a lot more people per resource. There is obviously no alternative with zero impact. Even walking uses nonrenewable resources. Cars are just much more wasteful than other modes of transportation.