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Week Thirty-Six - Urban Transport

Urban transport generates 2.1 tonnes CO2e per person per year

My kindergartner

- Mummy, when I'm a grown-up can I work in the same place as you so you don't get lost any more?

Confused person tries to navigate

Are we there yet?

Like Australia's national climate policy, I'm often lost. Between Google maps, an old street directory and my kindergartner, I usually get there in the end. But ironically, the last time I failed was on my way to a climate change film. I drove around in circles for half an hour, emitting all the way, then gave up and came home. Movement does not always mean progress.

How much CO2e comes from our transport?

Australians move a lot. Our transport system generates a whopping 19% of Australia's carbon dioxide and equivalent emissions (CO2e). And that's only counting the tailpipe emissions from the fuel.

How much CO2e to move the average urban Australian?

According to government data, the average city resident travels 10,175 kilometres by private vehicle and 1,295 kilometres by public transport each year. If done with a solo driver in a petrol car and a ride on a diesel bus, that transport generates 3 tonnes of CO2e each year. It's a huge chunk from a 20-tonne footprint.

But that only covers driving and public transport. We also walk, ride and scoot. I dug into local data for a more granular picture. The average Canberran travels less than the average Australian (no doubt thanks to our compact city) and generates almost 2 tonnes CO2e each year for urban travel. This is done by car (6,643 kilometres each year), bus (397 kilometres), walking (232 kilometres), bike (127 kilometres), motorbike (75 kilometres) and taxi (15 kilometres).

Averages are fiction. I know people who ride 127 kilometres in a day and people who don't ride that in a decade. Most of us pick a few favourite modes and stick to them. To see how an actual human travels, I logged my own habits. It turns out I generate around 1.1 tonnes of CO2e each year travelling by car (3,525 kilometres), bike (1,920 kilometres), walking (780 kilometres), bus (240 kilometres) and taxi (192 kilometres). I walk and ride a lot more than the average but I still drive a lot too, so there's plenty of room for improvement!

A woman on a scooter, a silver hatchback and a woman riding a bike

A few of the ways I get around town.

What's surprising?

It's no shock that a big chunk of emissions come from a fossil fuel car carrying one person. But I was astonished to see that diesel performs even worse. I'd often heard that diesel is environmental because it's a more efficient fuel. While it's true that diesel has a higher energy content, it emits more carbon than petrol when it burns. When you factor in better modern options like electric cars and consider the frequent diesel scandals, there's nothing green about it.

I was also surprised to see how much we walk for transport. But then I realised that most trips start and end on foot, whether you're going to your final destination, a bus stop or a car park. Walking is a really efficient way to get around on those very short trips.

How will I cut back?

Over the next month, I'll slash these transport footprints with the following experiments.

- Active transport. I'll spend a week using only active transport. I love riding but I'm not sure how my bike will carry my groceries, my kid and my fur babies.

- Mass transport. I'll test out Canberra's public transport and trial other mass-transit options. I'll also find out why we use so much less public transport in Canberra than in other cities.

- Better cars and better ways to use cars. I'll look at the best ways to use the worst vehicles and the new ones that should replace them.

How did I count this transport footprint?

The above figures cover tailpipe emissions for cars, motorbikes and buses. I've also counted embedded vehicle emissions (under 21% for cars on my modelling, but I've seen higher estimates elsewhere). But that's not the full picture.

- How many passengers? A car carrying three people effectively emits one-third less per person per kilometre than a car with just the driver. Public transport is highly efficient with peak-load passengers but terrible with only one person riding. I assumed an average of 23.8 passengers per trip for a bus and one person per trip for a car, but I'll model variations in later weeks.

- Vehicle servicing and infrastructure. All vehicles need servicing and spare parts. They also use roads, traffic lights and tram lines. These all generate emissions, more for some vehicles than others. For instance, motorbikes need frequent services and a big 4WD wears out a road faster than a pushbike. I've left out all this complexity.

- Fuel for active transport. If you ride a 100-kilometre commute each week, you'll burn more calories. In How Bad Are Bananas? Berners-Lee showed that cycling a mile could generate 65 grams, 260 grams or 2.8 kilograms of carbon, depending on what you eat. I covered food in Weeks Eleven - Eighteen and I suspect any impact is offset by the health benefits and reduced medical intervention from exercise. But try not to fuel your commute with air-freighted asparagus or steak.

- Congestion. Our cities are choking on congestion. Government data show that traffic delays and interruptions to traffic flow in Australia's six major cities account for around 13 million tonnes of CO2e. I haven't modelled this but it's one reason that an urban car, no matter how green, has a big environmental impact compared to a bus, tram, bike or foot.


While mass transport is usually an eco-friendly option, this doesn't apply to aeroplanes. Flying is the fastest way to fry the planet, as I discovered in Week Six and Week Twenty-Six. For personal travel or freight, always choose road over air. It doesn't matter if you drive a massive diesel SUV, it will still beat a plane full of passengers.

Flying is the fastest way to fry the planet

Still feel like flying?

Notes, data and spreadsheet calculations in 'Notes' section, Week Thirty-Six.


Updated after publication in line with emission factors provided by the federal Department of the Environment and Energy. Department calculations were slightly higher than mine, I've substituted in the official government figures where provided.