text: For starters, experts say we have to drastically reduce greenhouse gas emissions from tailpipes..passenger cars are responsible for 12% of greenhouse gas emissions in Europe, and up to 50% in some car-intensive areas in the U.S. Our planet is already polluted enough..why add more to it. For example; diesel trucks make up 67% of vechicles in France..which then adds more smog. In addition, Paris has more smog than othe European capitals. Once Paris had 147 microgrmas of particulate matter per cubic meter compared with 114 in Brussels and 79.7 in London, Reuters found. In the city of Bagota, Colombia their goal was to promote alternative transportation and reduce smog, violaters faced a $25 fine.