By 2025, you're not going to find diesel-powered vehicles in Paris, Madrid, Athens, or Mexico City, according to an announcement made by those city's mayors at this year's C40 Mayors Summit in Mexico City. We already knew that Paris was working to dramatically lower nitrogen-oxide (NOx) emissions in the next few years (it's already banned diesels built before 1997), and now other major cities are joining the bandwagon. Why are diesel-produced NOx emissions so bad?

It not only causes breathing issues but has also been linked to various types of cancer. "Today, we also stand up to say we no longer tolerate air pollution and the health problems and deaths it causes – particularly for our most vulnerable citizens," stated Paris mayor Anne Hidalgo. "Big problems like air pollution require bold action, and we call on car and bus manufacturers to join us." But what will take the place of diesel vehicles, specifically buses used for public transportation? Mexico City's mayor, Miguel Angel Mancera, wants to expand alternative transportation methods like the Bus Rapid Transport system, which is already in use, the subway, as well as a 19th century invention, called the bicycle.

In fact, Athens' mayor, Giorgos Karminis, went a step further by declaring that his "goal is to ultimately remove all cars from the center of Athens in the years to come." Automakers who once relied heavily on diesel sales, especially in Europe, are now rapidly developing EV technologies to take the former's place. Volkswagen, who we all know has had a rocky relationship (putting it lightly) with diesels, has already announced it wants to sell one million EVs by 2025. This diesel-ditching trend likely won't end with these four cities, and will doubtless become an inspiration for others to follow. Also, BMW, Ford, Mercedes, and VW just joined forces to electrify Europe with hundreds of new fast charging EV stations.