a web app to compute travel CO2eq for different means of transport worldwide

The work presented here is independent and not-for-profit. This work has been carried out on a voluntary basis.

The aim of this web app is to present precise carbon inventories per passenger for each mode of transport and each journey. These results enable users to make informed choices in the context of reducing their greenhouse gas emissions to mitigate climate change. To put these results into context, total net yearly per-capita emissions should not exceed 2 tons CO2eq in 2050 to limit global warming below +2°C.

You can have a look at https://lowtrip.fr/.

How the emissions are calculated?

To calculate CO2 equivalent emissions per person, we multiply the distance of a journey (km) by the corresponding emission factor (mass of CO2 equivalent per person per km) of a mean of transport. For a mutlistep journey, these emissions are summed over the different steps:

$$CO_2eq = \sum_{step} Distance(km) \times Emission \: Factor(kgCO_2eq / km) $$

Estimation of distances

Mean of Transport	Distance
Train	OpenStreetMap network
Car & Bus & eCar	OpenStreetMap network
Bike route	OpenStreetMap network
Plane	Geodesic distance and average detour
Ferry & Sailboat	Approximation of shortest path

What do emission factors depend on?

Mean of Transport	Variable
Train	Visited countries
Bus	-
Car	Number of passengers
Electric car	Visited countries & Number of passengers
Bike route	-
Plane	Distance of journey
Ferry	User-specified parameters
Sailboat	- ; improvements on the way

Emissions factors consider usage (linked to the manufacture and use of energy to move the vehicle) as well as infrastructure and vehicle construction where these are significant. The table below summarizes the types of emissions taken into account by lowtrip. Empty cells mean that the related emissions did not contribute significantly to the result and are therefore excluded to facilitate understanding and readability for the user.

Mean of Transport	Usage	Vehicle construction	Infrastruture construction
Train	✅		✅
Car & Bus & eCar	✅	✅
Bike route		✅	Not found
Plane	✅
Ferry	✅		Not found
Sailboat	✅		Not found

All assumptions, data and sources used are available in the methodology document.

How to launch the app?

Prerequisites

Have docker installed

Launch the app

At the root of the directory, run:

docker-compose up --build

You can now connect to http://localhost:3000 to test the application.

Note: If you want to launch them in the backgroup and leave them running, you can add the flag -d or --detach.

Rebuild and restart a service

At the root of the directory, run:

docker-compose up --build <service name: backend or frontend>

Stop the app

At the root of the directory, run:

docker-compose down

How to launch the app components separately?

Prerequisites

Have python & node installed

Launch the backend

cd backend

# create a python environment and activate it
python -m venv lowtrip-venv
source lowtrip-venv/bin/activate

# install the dependencies
pip install -r requirements.txt

# launch the app
gunicorn app:app

You can format the code with ruff:

pip install ruff
ruff format

Launch the frontend

cd frontend

# install the dependencies
npm install

# launch the app
npm start

How to cite this work ?

Bonnemaizon, Xavier, Ni, Clara, Gres, Paola & Pellas, Chiara. lowtrip (2024). https://lowtrip.fr