Every rush hour, bumper-to-bumper traffic belches out diesel fumes along Madrid's Gran Via, a six-lane artery that bisects the Spanish capital. Art Deco facades line the grand boulevard.
But they're blackened with soot.
"The pollution hurts my eyes, and I can feel it in my throat," says commuter María Villallega, 48, who lives in the city center and walks to work. "I don't own a car myself, and I'll be happy when they're not allowed here anymore. We need to protect the planet, and ourselves."
In three years, Gran Via will be off-limits to all these cars — only public buses, taxis, cyclists and pedestrians will be allowed. It's part of Madrid Mayor Manuela Carmena's two-pronged plan to cut air pollution: All cars will be banned from Gran Via in three years, and she has pledged to ban most diesel-powered cars from the entire city by 2025.
Madrid's air pollution has exceeded European Union limits for the past eight years running — in part, because half of all cars here, and across Europe, run on diesel. By comparison, only about 3 percent of cars in the U.S. are diesels.
Since the 1990s, European governments have levied lower taxes on diesel than on gasoline, because diesel was thought to be cleaner.
"Diesel cars go farther on a gallon of fuel, so they produce less carbon. European governments decided diesel technology was the way for Europe to hits its carbon dioxide targets," explains Mike Rosenberg, an auto industry analyst at Spain's IESE Business School.
German automakers "lobbied very hard" for a switch to diesel prominence in the 1990s, Rosenberg says. Diesel was seen as a win-win — with lower fuel consumption and lower carbon emissions.
But while less carbon is better for the planet, diesel cars emit something else that's worse for human beings: nitrogen oxides and soot — tiny black particles that contain toxins.
The World Health Organization estimates that outdoor air pollution led to some 3 million premature deaths worldwide in 2012.
So with toxins fouling the air in its big cities, some parts of Europe are doing a 180-degree turnaround on diesel. In addition to Madrid, Paris and Athens also plan to ban diesel vehicles by 2025. All the cities announced their plans at a global mayors' conference in December.
While that may be promising for the environment, it's created "total panic" among car manufacturers, says Javier Quintaná, a salesman at a large Ford dealership in Madrid. Half of his inventory is diesel cars. He even drives a diesel himself. He says that while manufacturers are switching to producing more gas, hybrid and electric cars, they worry they'll be unable to sell all the diesel cars they've already made — like the ones parked on his showroom floor.
Quintaná says dealers are scrambling to offer customers incentives to buy diesel cars in the short term, while they still can.
"What we're doing is modifying [diesel] cars to limit pollution. In the factory, we can use additives so the cars emit less — to comply with air quality rules," Quintaná explains. "And yes, we've also lowered the prices — to get people to buy these diesels."
But it's a tough sell. Madrid has already hiked fees for registration, road tax, emissions tests and parking permits for diesel cars, but not for electric ones or those running on gasoline. In the past four months alone, sales of hybrid and electric cars have gone up by 90 percent in Madrid.
Quintaná says a majority of his vehicle sales have been diesel in recent years, but he's been selling mostly gasoline cars since plans for the diesel ban were announced late last year. All the diesel cars he's trying to sell now will be banned from Madrid's roads eventually, no matter what their emissions are, though they'll still be allowed outside the city limits.
Some of the diesel cars no one wants to buy end up being unloaded onto a vast parking lot south of Madrid, on the plains of La Mancha, where unsold vehicles sit and rust. It's a car depot where rental car companies unload their inventory, and used car buyers come to find deals.
"I have no idea what to do with all these diesels," says Miguel Buendía, who sells used cars and scrap metal on the lot. "Their value will keep dropping, and if I can't sell them in this country, I'll have to sell them elsewhere."
For that, says auto industry expert Rosenberg, a new industry may pop up.
"There will be this enormous number of used diesels which no one wants to buy, that you won't be able to drive in the city," he says. "My guess is an industry will appear out of nowhere to ship all these cars further east and further south, to Eastern Europe and Africa."
In other words, to places where air pollution in many cities is even worse than in Europe.