The carbon footprint of different transportation modes varies depending on factors such as vehicle efficiency, occupancy, and fuel type. Here are the approximate carbon emissions per passenger-mile for various transportation modes:1. Car: The average carbon footprint for a car is around 0.96 pounds 0.435 kg of CO2 per passenger-mile. This value can vary depending on the fuel efficiency of the car and the number of passengers. A more fuel-efficient car or a car with more passengers will have a lower carbon footprint per passenger-mile.2. Bus: The carbon footprint of a bus depends on its occupancy. A fully occupied bus can have a carbon footprint as low as 0.14 pounds 0.064 kg of CO2 per passenger-mile. However, if the bus is less occupied, the carbon footprint per passenger-mile will be higher.3. Train: Trains are generally more energy-efficient than cars and buses, with an average carbon footprint of around 0.36 pounds 0.163 kg of CO2 per passenger-mile. This value can vary depending on the type of train and its occupancy.4. Airplane: The carbon footprint of air travel is relatively high, with an average of 0.53 pounds 0.240 kg of CO2 per passenger-mile for short-haul flights and 0.44 pounds 0.200 kg of CO2 per passenger-mile for long-haul flights. The carbon footprint of air travel can be reduced by increasing airplane occupancy and improving fuel efficiency.These transportation modes contribute to carbon emissions in the environment by burning fossil fuels, which release CO2 and other greenhouse gases. These emissions contribute to climate change and have various negative impacts on the environment, such as rising sea levels, extreme weather events, and loss of biodiversity. Reducing the carbon footprint of transportation can be achieved by using more energy-efficient vehicles, increasing occupancy, and transitioning to cleaner energy sources.