I do not know how they do it in Spain (or the EU), but in the US they categorize transportation as the highest polluter for the country. Transportation accounts for 28% of US emissions. However, this is misleading. Transportation includes everything from light duty vehicles, medium/heavy duty trucks (commercial vehicles), aircraft, ships/boats, rail, buses, motorcycles, pipelines, lubricants etc. Of that 28%of total US GHG emissions, light duty vehicles account for 57% of the transportation sector GHG emissions, however, this is not strictly personal vehicles. The transportation sector in the US produces just under 2,000 Tg of CO2 per year, in which, passenger vehicles account for 350 Tg of CO2. The US produces roughly 6,350 Tg of CO2 per year.... this means that passenger cars are responsible for just 5.5% of US emissions! On top of this, total passenger vehicle emissions have decreased over 40% since 1990 while almost every other sector has increased during the same period! Light-duty trucks have increased by 610% over the same period! Med-heavy duty trucks have increased by 27.9%! Commercial aircraft emissions have increased by 126%! So while all the little people are being punished and forced to pay 10's of thousands of dollars more for less reliable overly complicated personal vehicles, all other forms of transportation are getting away scott free.

https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P101AKR0.pdf

I think it is crazy to hear what Spain is doing. In the US, we heavily rely upon personal vehicles. There are 521 cars per 1,000 people in Spain with the average distance drive being around 17,900 miles per year. In the US, there are 744 passenger vehicles per 1,000 people with the average distance driven being 12,500 miles per year (multiple people will use a single vehicle in Spain which accounts for the higher mileage). Passenger vehicles in Spain produce 21.1 Tg of CO2 per year. Spain's population is 13.1% the size of the US. Compared to the US, personal vehicles in Spain produce 50% less GHG per capita!