Most conversations about reducing your environmental footprint focus on the same handful of options: buy an electric car, go vegetarian, fly less, switch to solar. These are real and meaningful choices. But there's one action that consistently outperforms expectations in the numbers — and most people don't think of it as an environmental choice at all.
Carpooling.
Not because it's fashionable or because there's a government campaign behind it. Because the maths is genuinely compelling — and because it's something you can do tomorrow, without spending any money, without changing your diet, and without installing anything on your roof.
The baseline: how much CO₂ does a car actually emit?
The average Australian passenger car emits approximately 170 grams of CO₂ per kilometre, based on the national fleet average published by the Department of Infrastructure. Newer cars emit less; older cars more. But 170g/km is a reasonable working figure for most commuter vehicles.
For a typical 25 km one-way commute — representative of many Australian suburban commuters — that's:
25 km × 170g CO₂/km = 4,250g = 4.25 kg CO₂ per one-way trip
8.5 kg CO₂ per return commute day
~1.5 tonnes CO₂ per year at 4 days/week, 45 weeks
That's just the commute. It doesn't include weekend driving, errands, or holidays. The commute alone — if you drive solo — accounts for roughly 1.5 tonnes of CO₂ per year for a typical suburban Australian worker.
What carpooling actually changes
Here's the key insight that most people miss: when you add a passenger to a car trip that was already happening, the emissions of that trip don't double. The car emits the same amount of CO₂ whether one person is in it or four. The fuel consumption difference between one occupant and two is marginal — maybe 3–5% more fuel for the additional weight.
So when a passenger joins an existing commute, you're not adding a car to the road. You're removing one. The passenger's alternative — driving their own car — produces 4.25 kg of CO₂ per one-way trip. By joining someone else's car, they reduce that to near zero. The driver's emissions are unchanged.
The net saving per passenger, per one-way trip: approximately 4 kg of CO₂.
| One-way commute distance | CO₂ saved per trip (1 passenger joining) |
Annual saving (4 days/week, 45 weeks) |
|---|---|---|
| 10 km | ~1.6 kg CO₂ | ~576 kg (~0.6 tonnes) |
| 20 km | ~3.2 kg CO₂ | ~1,152 kg (~1.2 tonnes) |
| 30 km | ~4.9 kg CO₂ | ~1,764 kg (~1.8 tonnes) |
| 40 km | ~6.5 kg CO₂ | ~2,340 kg (~2.3 tonnes) |
| 50 km | ~8.2 kg CO₂ | ~2,952 kg (~3.0 tonnes) |
For a typical 25–30 km commute, a regular carpooling arrangement prevents roughly 1.5–1.8 tonnes of CO₂ per year. That's a single passenger joining a single driver's existing commute, four days a week.
How does this compare to other green choices?
This is where it gets interesting. Let's put the carpooling saving in context against other popular environmental actions.
| Action | Annual CO₂ saving | Cost / effort |
|---|---|---|
| Carpooling 4 days/week (30km commute) | ~1.8 tonnes | Free — saves money |
| Going vegetarian | ~0.5–0.8 tonnes | Lifestyle change |
| Switching to an EV (avg Australian grid) | ~1.0–1.5 tonnes vs petrol car | $40,000–80,000 upfront |
| Installing rooftop solar (6.6kW system) | ~2.5–3.5 tonnes (household) | $5,000–8,000 upfront |
| Skipping one long-haul flight (return) | ~1.5–3.0 tonnes | One-off; not repeatable annually |
| Switching to green power | ~1.5–2.5 tonnes (household) | ~$200–400/year premium |
Carpooling a 30 km commute four days a week saves more CO₂ than going vegetarian. It saves a comparable amount to switching to an EV — without the $60,000 price tag. And unlike skipping a flight, it's a saving you make every single week, compounding over years.
The most effective environmental action most Australian commuters could take isn't buying an EV. It's filling the empty seats already in their car.
Australia's commuting problem in numbers
Australia has one of the highest rates of solo car commuting in the developed world. According to the Bureau of Infrastructure and Transport Research Economics (BITRE), approximately 69% of Australian commuters drive to work alone. The average vehicle occupancy for commuter trips is around 1.1 — meaning the typical commuter car is 75% empty.
The total distance driven for commuting in Australia is estimated at over 80 billion kilometres per year. At 170g CO₂/km and 1.1 average occupancy, that's roughly 136 million tonnes of CO₂ from commuting alone — about 27% of Australia's total transport emissions.
If average vehicle occupancy for commuting increased from 1.1 to just 1.5 — still well below capacity — the CO₂ saving would be in the order of 45 million tonnes per year. That's more than the entire annual emissions of many small countries.
You don't need every car to be electric to make a meaningful dent in transport emissions. You need more people in the cars already on the road.
The Scope 3 angle for employers
For Australian businesses working toward net zero commitments, commuting is a significant and often underestimated source of emissions — classified as Scope 3 (indirect emissions from the value chain). Unlike Scope 1 and 2 emissions, which come from a company's own operations and energy use, Scope 3 commuting emissions are harder to control because they depend on employee behaviour.
Carpooling is one of the few Scope 3 interventions that doesn't require infrastructure investment or policy mandates. It works through behaviour change facilitated by the right platform — which is exactly what Herdy provides.
Employers who run a carpooling programme through Herdy can measure and report the resulting CO₂ reduction with reasonable precision: distance per trip, frequency, number of participants, vehicle type. That's quantifiable Scope 3 abatement — the kind that satisfies ESG reporting requirements and goes beyond vague "awareness campaigns."
Why carpooling is underrated as an environmental action
Part of the reason carpooling doesn't get the environmental credit it deserves is that it doesn't look like an environmental action. You're not buying something green. You're not installing something. You're not changing your diet. You're just sharing a car.
That ordinariness is actually the point. The most scalable environmental actions are the ones that don't require people to make sacrifices or major financial commitments. Carpooling saves money, saves time (for the passenger), and prevents over a tonne of CO₂ per year — and the only thing it requires is finding someone going the same way.
That used to be the hard part. It isn't anymore.
