Driving & the Environment
Road transport accounts for a significant share of the UK's total carbon emissions. But unlike some sources of pollution, driving emissions are something individual drivers can meaningfully influence — through the routes they choose, the speed they drive, and how they use their vehicle.
This page explores the environmental impact of driving in plain terms, with practical, evidence-based steps that actually make a difference.
The numbers — how much CO2 does driving produce?
To put that in perspective — a typical 200-mile motorway journey in an average petrol car produces around 40-50 kg of CO2. That's equivalent to charging a smartphone roughly 5,000 times, or the amount a single tree absorbs in about two years.
The good news: Small changes in how you drive can reduce emissions by 10-25% with no change to your vehicle. Speed is the single biggest factor you control.
How speed affects fuel consumption and CO2
The relationship between speed and fuel consumption isn't linear — it follows a curve. Most petrol cars are at their most efficient between 45-60mph. Above that, air resistance (drag) increases rapidly, forcing the engine to work much harder for each additional mile.
| Speed | Relative fuel efficiency | vs 60mph | CO2 impact |
|---|---|---|---|
| 50 mph | Best efficiency | ~2% better | Lowest |
| 60 mph | Very good | — | Low |
| 70 mph | Good | ~5% worse | Moderate |
| 80 mph | Noticeably worse | ~13% worse | Higher |
| 90 mph | Poor | ~21% worse | Much higher |
| 100+ mph | Very poor | ~32% worse | Highest |
The physics here is straightforward — air resistance increases with the square of speed. At 70mph you're pushing through 36% more air resistance than at 60mph. Your engine has to work significantly harder just to maintain that extra 10mph.
The impact of a typical journey
Here's how a 200-mile motorway journey (typical London to Manchester distance) compares across different speeds in an average 40mpg petrol car:
Beyond speed — other factors that affect emissions
🔧 Vehicle maintenance
A poorly maintained car can use significantly more fuel than a well-serviced one. Under-inflated tyres increase rolling resistance — just 10 PSI below the recommended pressure can reduce fuel economy by around 3%. A blocked air filter can reduce efficiency by up to 10%. Regular servicing pays for itself in fuel savings.
❄️ Air conditioning
Air conditioning increases fuel consumption by around 5-20% depending on the outside temperature, vehicle, and how hard the system is working. At motorway speeds, keeping windows closed and using air conditioning is typically more efficient than opening windows — which increases drag. In urban driving, opening windows is usually better.
⚖️ Weight and load
Every extra 50kg in the car increases fuel consumption by roughly 1-2%. Roof boxes and bike racks add significant drag — a roof box at motorway speed can increase fuel consumption by 10-25% even when empty. Remove them when not in use.
🛑 Smooth driving
Harsh acceleration and late braking waste a huge amount of energy. Anticipating traffic and maintaining a smooth, steady speed — particularly in urban driving — can reduce fuel use and emissions by 15-30% compared to aggressive driving. This is the basis of "hypermiling" techniques used by fuel economy enthusiasts.
🔌 Electric and hybrid vehicles
Electric vehicles produce zero tailpipe emissions, though they do have emissions associated with electricity generation and battery manufacturing. In the UK, as the grid becomes cleaner, the lifetime emissions of electric vehicles continue to fall. Plug-in hybrids can dramatically reduce emissions on shorter journeys where they run entirely on electric power.
What difference does one driver make?
Individual action matters more than it might seem. If a driver covers 10,000 miles per year and reduces their average motorway speed from 80mph to 70mph, they'd save approximately: