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CO₂e · time · cost

Every journey has a footprint.

A smarter way to compare travel by CO₂, time, and cost.

I flew to Lisbon for a two-week entrepreneurship programme at LSE. While planning the trip, I found it surprisingly difficult to balance cost, travel time, and carbon emissions. I kept switching between different websites and calculating my environmental impact by hand, so I built a tool to make those trade-offs simple.

I used this tool throughout my time in Portugal to plan trips to Porto, Sintra, and Cascais. The programme also inspired me to travel more sustainably, so I chose trains over renting a car and relied entirely on Portugal's metro, tram, and rail networks. Having all the information in one place made it much easier to compare options and choose lower-carbon journeys.

After seeing how useful it was on my own trip, I decided to publish the tool so other students and anyone who wants to make more sustainable travel choices can use it too.

Calculate my journey →

01 · THE PROBLEM

The challenge of sustainable travel

Travel is worth doing, but every journey has a cost, and the same destination reached by different modes produces wildly different emissions. The challenge is not picking the fastest or the cheapest. It is balancing affordability, convenience, and sustainability.

Plane

  • Higher CO₂
  • Shorter time
  • Convenient over distance

Bus

  • Medium CO₂
  • Lower cost
  • Slower, widely available

Train

  • Lower CO₂
  • Comfortable
  • Competitive on medium routes

02 · THE IDEA

Turning research into one tool

Instead of comparing options by hand, I built a calculator that puts environmental impact, cost, and time in one place.

Environmental impact

Estimated CO₂e for each mode, the difference between them, and the emissions saved by switching to a cleaner option.

Cost

An approximate price for each mode, so you can weigh value against impact rather than guessing.

Time

The duration of each option, and the honest trade off between speed and sustainability.

03 · HOW IT WORKS

How it works

  1. 1 Enter your journey.
  2. 2 Compare the options.
  3. 3 Choose your balance.
Illustrative example: Luxembourg to Paris
ModeTimeCostCO₂
Plane1 h€80120 kg
Bus5 h€2535 kg
Train3 h€6015 kg

Rounded illustration only. The live calculator computes its own figures for your route, so exact numbers will differ.

The most sustainable choice is not always the cheapest or the fastest. This helps you decide knowingly.

04 · THE GOALS

UN Sustainable Development Goals

This project maps to five specific SDG targets, not just headline goals.

Target definitions from the United Nations Sustainable Development Goals.

SDG 7.2

Renewable share of the energy mix

My Portuguese trains were near zero carbon because 68% of Portugal's electricity was renewable in 2025, hydro 27% and wind 25%, and the last coal plant closed in 2021. The grid did the work, not me.

SDG 11.2

Access to safe, affordable, sustainable transport

Sintra and Cascais are both on the CP suburban line for a couple of euros. I never needed a rental car. 11.2 is not advice, it is infrastructure that makes the good choice the easy one.

SDG 12.b

Tools to monitor sustainable tourism impacts

This site is that tool. Targets ending in a letter are means of implementation targets, which is exactly why building a monitoring instrument counts against 12.b.

SDG 13

Climate action

Where I failed. I flew, and it was 95% of my footprint. Say so plainly.

SDG 4.7

Education for sustainable development

I published the tool, the method, and the data openly so other students can run the same comparison.

05 · THE POINT

Small choices create collective change.

Sustainable travel does not mean travelling less. It means knowing the impact and choosing well when you can.

TERRA TRANSITroute · co₂e · globe
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