These days, everyone seems to be talking about innovating the transportation sector. Innovation is inherently exciting. Hyperloop? E-scooters? Flying taxis? Pogo sticks?! I’m excited just thinking about it all. Well, maybe not the pogo sticks.

But what if we could drastically reduce carbon emissions with existing technology?

That technology, ladies and gentlemen, is the good old bus. In this post, I ask the following question: what if we replaced cars with buses for our daily commute to work?

Let’s start with a bird’s eye view: most buses are in cities. Why is that important?

Cities are an important contributor to climate change

It’s important because cities make up a big share of the world’s carbon emissions: one study found that the top 100 urban areas by carbon footprint contain 11% of the world’s population but drive 18% of the global carbon emissions. It also cited studies that found similar results. 

On top of that, the global urban population is increasing. The World Bank estimates that by 2050, 70% of the world’s population will be city-dwellers. 

So cities pollute disproportionately to GHG emissions, and their share of the total population is growing. While cities obviously provide desirable accommodations to their residents, on its face, this presents a problem for preserving Planet #1.

Transportation is a big contributor to cities’ GHG emissions

Next question: when it comes to cities’ carbon emissions, how big of a driving factor is transportation? The answer varies by city. In 2017, 72% of Salvador’s carbon emissions came from the transportation sector. That number was 47% for San Francisco and just 7% for Sydney. There are a number of factors that can influence the answer, but in most cases, transportation is a huge component. 

Moreover, there is evidence that contribution of transportation industry to climate change has been growing since 1990, while the share of other industries’ contributions have declined.

To summarize: cities are big polluters, they are growing in size/number, and transportation is an increasingly important driver of their pollution.

Buses are cheaper than cars

Before we get to lowering carbon emissions, let’s talk about cost. Clearly, a big sticking point when it comes to rolling out a bunch of new buses is the price tag. No one wants to pay more for something they value less than their current mode of transportation.

As a thought experiment, let’s pretend we got rid of all the cars people drive to work and replace them with buses, using San Francisco as an example. For my assumptions, I’ll use 2012 data from the San Francisco Municipal Transit Authority.

According to SFMTA, 33.3% of workers used public transit, 36.6% drove alone, 7.6% carpooled, 2.4% took a cab or motorcycle, and the rest walked or biked to work, or worked from home. In a city with about 440,000 jobs, that means about 200,000 people took a car to work. Given the carpooling stats, let’s say that’s 180,000 cars.

There are a range of bus sizes, but let’s assume (based on this source) that bus capacity is 40 riders. That means we need 5,000 buses for 200,000 workers. Since it’s unrealistic to assume the buses operate at full capacity, let’s say we need 7,500 buses.

If operating a bus over the course of its lifetime costs $1.35 million, the total investment cost for 7,500 of them is about $10 billion. Furthermore, no cars means no revenues from parking or traffic violations for the city. Based on the SFMTA data, let’s add $2 billion per year, for a total of $12 billion. Seems like a lot. 

And for simplicity, let’s assume the new buses are completely paid for by those 200,000 former drivers. That works out to $60,000 per person. Still seems like a lot.

But let’s assume the average useful life of a bus is 12.5 years. Now we’re down to $4,800 per person per year. This story pins the cost of owning and maintaining a car at $9000 per car per year. With 180,000 cars driving 200,000 workers, that works out to $8,100 per car per year.

That means, given these assumptions, replacing cars with buses would save the average driver $3,300 per year.

To emphasize: even removing carbon emissions from the equation, replacing cars with buses would save money.

Buses are more climate-friendly (duh)

The point of this post is not to demonstrate the cost savings potential (at least in an accounting sense) of expanding bus fleets. That’s just icing on the cake. The real question is by how much carbon emissions could be lowered. 

To calculate that, we first need the distance each of our former drivers travels to work. This source says 8 miles, on average. However, it doesn’t differentiate by type of transportation and I’m not sure if it includes people who don’t live in San Francisco. Intuitively, I would think drivers live further away than public transit commuters, on average. However, I’m not sure we can make an apples-to-apples comparison to the SFMTA data. Let’s stick to an average commute distance of 8 miles.

According to the EPA, the average passenger vehicle emits 404 grams of COper mile. Based on Wikipedia and my calculations, a typical bus emits about 1390 g COper mile

In total, 180,000 cars driving 16 miles per day, 245 working days per year would emit 285,000 metric tonnes of CO2

Replacing all of those car trips with bus trips would result in a savings of 245,000 metric tonnes of CO2 per year, and that’s only from commuting to work with buses.

Bus travel frees up time

There’s one other benefit to bus travel, and public transit in general, that’s important to point out. It might seem obvious, but when you’re riding the bus, you’re not driving. That means more time to use your brain. You can get some work done on your laptop. Write a blog post. Read a book. What do all of these things have in common? You can’t (or at least, you shouldn’t) do them while operating a motor vehicle.

So, to sum it all up: buses can save money, save the climate, and provide us with more time, the scarcest resource of all.

The drawbacks and caveats

“A man who, beyond the age of 26, finds himself on a bus can count himself a failure.”

Margaret Thatcher

The biggest hurdle to bus travel seems to be cultural attitudes. It is associated with lower class. People enjoy being alone in their car. Heck, people enjoy driving cars. 

I’ll admit this is a serious problem to which I don’t have a solution ready. Effecting a cultural shift in favor of bus transit has been a political hurdle for decades. 

Lastly, a caveat to all of the conclusions in this post: you might have issues with some of the assumptions I used. But while they might be slightly off, they are in the ballpark. For example, you might think that 7,500 buses isn’t nearly enough to accommodate 200,000 commuters. OK, you could bump that up to 13,500 buses and still see cost savings. Or maybe you think that having so many diesel buses would harm local air quality. OK, e-buses cost even less over their useful life.


To conclude, the point of this post isn’t really to sing the praises of buses (OK, maybe a little bit). The point is that we have the tools at our disposal to reduce climate change with existing technology. While I strongly support investments in R & D for clean tech, we can put a big dent in carbon emissions with something as simple as buses.