IT IS a blindingly affluent city where Bentleys and Ferraris have become nearly as common as Fords and Volkswagens. So it does not come as a surprise that Dubai has a growing problem with traffic (see picture). The local rulers have explored all the conventional ways to get traffic moving again, including higher prices for parking, fuel and insurance. But at a recent conference in Hamburg, Hussain Lootah, director-general of the Dubai Municipality, revealed that the city may opt for a more draconian approach: setting an income threshold for vehicle ownership. Mr Lootah’s approach is unlikely to be copied widely, but mayors of other big cities around the world can certainly sympathise—and are starting to think about taking drastic actions of their own, including outright car bans in inner cities. At some point they will run out of options: efforts such as inner-city tolls, pioneered by London and Singapore, or letting only motorists with certain number plates enter a city, as Paris did recently, may not be enough to reduce traffic and pollution. The problems will only get worse: the number of vehicles sold globally each year will grow from around 80m today to more than 100m by the end of the decade, according to IHS Automotive, a market research firm.

There are already a handful of car-free communities around the world. But these are typically small and often tourist destinations that seek to create a throwback in time, such as Sark Island, in the English Channel, and Michigan’s Mackinac Island. The largest car-free urban area is probably Venice, where it is impossible to build roads and bridges to link the more than 100 small islands the city sits on.

Yet pedestrian malls and other car-free zones keep popping up in cities around the world; a page in Wikipedia lists dozens, mainly in city centres. Some cities are considering ways to limit core city access to “green” machines, such as battery-electric vehicles or plug-in hybrids. Hamburg is perhaps the furthest along. Although Germany’s second-largest city does not want to go “car-free” within two decades, as many media reports wrongly stated earlier this year, it is weaving a “Grünes Netz”—a green network of parks, playgrounds, sports fields, bike paths and the like which will allow pedestrians or cyclists to more easily navigate through the city. In other words, cars won’t be banned, but get downgraded—a big deal in a country which loves its cars almost as much as America.

Such radical plans may fly in a city such as Hamburg where the Greens are a force to be reckoned with. But in many other cities the political resistance even to less far-reaching measures is hard to overcome. Michael Bloomberg, New York’s former mayor, tried twice to introduce a congestion charge for much of Manhattan, but his plans were rejected by state lawmakers (though proponents are pushing his recently elected successor to give it another go). In the meantime, the city has put in place a few more car-free zones, such as the one near the pedestrian-crowded theatre district.

Perhaps technology will save Manhattan from carmageddon. Those who prefer not to restrict personal mobility are hoping that inventions such as autonomous vehicles will allow far more vehicles to travel smoothly on traffic-snarled streets. They could dramatically increase roadway throughput by, among other things, allowing vehicles to platoon only a few feet from each other, explains Andy Palmer, Nissan’s global product chief.

Such mobility wonders are some time off, however: the first autonomous vehicles won’t roam the streets before 2020. Dubai certainly won’t wait that long. The number of cars is the “biggest challenge” for the country’s future, explained Mr Lottah. “Everybody has their luxury life, but the capacity of our roads cannot take all of these cars without ownership laws.” Whereas the mostly rich Emiraties and expats will get to keep their cars, the mostly low-paid guest workers, who make up the majority of Dubai’s population, have to settle for mass transit.