A new book assesses the myriad technologies available to make cars pollute less as they spread across the world. But, Bradford Plumer writes, no new gizmo is likely to change one hard truth: we need to rethink our automotive way of life. Two Billion Cars: Driving Toward Sustainability Daniel Sperling & Deborah Gordon Oxford University Press Dh88 Late-19th-century Germany gets bragging rights as the birthplace of the four-stroke internal combustion engine, but all due credit for humanity's long-standing love affair with the automobile must go to the United States of America. "The motor car was poetry and tragedy, love and heroism," Sinclair Lewis rhapsodised in his 1922 novel Babbitt, noting that car ownership in America had already become "an aspiration for knightly rank". By 1950, 60 per cent of US households had what Lewis dubbed "a shuttle of polished steel" in the garage. A circular, self-sustaining logic came into play: the fact that so many people were driving meant that the nation's planners had to pave more highways and freeways, had to widen city streets and de-emphasise mass transit, had to build sprawling suburban neighbourhoods with cul-de-sacs so that children had quiet refuges to play, far from the roaring traffic - and all this infrastructure meant the motor car evolved from a knightly aspiration to an outright necessity for the peasants. It took longer for the romance to blossom in Europe and the Soviet Union, as Brian Ladd recounts in Autophobia, his diverting history of mankind's oft-turbulent relationship with the automobile. As late as 1954, the West German chancellor Konrad Adenauer mused about founding an "anti-automobile party" to protest the swelling parade of drivers who were clogging Europe's narrow urban streets and endangering its pedestrians. French intellectuals wondered if these hulking machines were dehumanising (there's a reason so many postwar French films evince a grim fascination with car crashes - think Godard's Weekend). Most Western Europeans, though, rallied around the automobile as a symbol of consumer freedom, and architects like Le Corbusier - who wanted European cities to reinvent themselves to accommodate motor traffic - carried the day. Europe may have higher petrol taxes and stricter fuel-economy rules than the United States, but the car is still monarch; in modern-day Germany, few politicians dare suggest a speed limit for the Autobahn. Now China, India and the rest of the developing world want to join the party. Already, honking hordes of cars and lorries are muscling aside bikes and passersby on the streets of Mumbai and Beijing, while the prospect of ultra-cheap cars like the Tata Nano, expected to retail in India for a piffling 100,000 rupees (Dh7,360), will only accelerate this trend. Between 2000 and 2020, the global car population is expected to double to more than one billion vehicles; by midcentury it could zoom past two billion. Two billion petrol-guzzling, fume-spewing cars. On one level, it's natural to embrace this diffusion of prosperity. Who'd want to deny millions of Indians and Chinese the pleasures of the road trip, the freedom to pack up and rumble off wherever they please? But there's a problem: Apart from the congestion and carnage (China saw at least 73,000 auto fatalities in 2008), those cars and lorries also emit all sorts of toxic pollution. Beijing's air has already curdled into a thick grey soup thanks to its growing vehicle emissions. Worse still is carbon dioxide. The climate science is clear on this: if China and India add one billion new standard-issue, gas-guzzling vehicles to the road, the Earth will heat to calamitous levels. To avoid that unhappy fate, as Daniel Sperling and Deborah Gordon warn in their new book Two Billion Cars, the world has to rethink the automobile as we've known it for the past century. Until now, western countries have just tinkered around the edges of the basic car concept - adding catalysers to soak up air pollution or tweaking mileage standards - hoping that painless tech fixes can forestall the day we need to make more radical changes, or worse, alter our auto-centric way of life. But that day may finally be upon us. Sperling and Gordon have both worked extensively on transportation issues in California, a state that, in many ways, provides a window into both the automobile's past and future. Los Angeles, once described as "17 freeways in search of a city", has long been the epicentre of car culture - after the Second World War, the city had the highest rates of auto ownership in the world. But LA is wedged between two mountain ranges and subject to frequent atmospheric inversions, causing the urban air to stagnate for days on end and turning the city's vehicle emissions into a hideously thick coat of smog (in the first major case, in 1943, residents vomited in the street and blamed the "petrol attack" on a local chemical plant). The postwar smog invasion led to the creation of the California Air Resources Board and concerted efforts to improve not just air quality, but fuel economy, too. In the 1990s, the state's "zero-emissions vehicle" rule helped spawn GM's short-lived electric car and prodded Toyota to begin research into what would become the Prius, whose electric motor is recharged by a petrol engine. Today, as the state embarks on an audacious climate-change plan, there's been no shortage of ideas on how to end the hegemony of the petrol-burning internal combustion engine and curtail carbon-dioxide emissions from the transport sector. If we could just do that, a two-billion car future might be survivable. But what are those alternatives? Sperling and Gordon scrutinise the panoply of ideas on offer, from fuel-economy standards to hybrids to biofuels of the future. None, alas, are easy to implement, and none provide an obvious cure-all. The simplest near-term step is to make petrol-burning cars more fuel-efficient. Europe and Japan have pioneered this trail - the average British passenger car now gets about 38 miles to the gallon, compared with 22mpg in America, where Detroit's automakers have lobbied ferociously against tighter standards. China, too, has roared ahead of the United States on fuel economy (requiring a 43mpg fleet average for small cars), though its ambitious rules are loophole-laden and difficult to enforce. So there's room to improve, but this approach also has its limits: Even efficient combustion engines waste about two-thirds of the fuel they burn, and many further improvements will only come from making the car chassis smaller and lighter. Plus, a world populated by two billion petrol-burning cars getting 60 miles per gallon would still mean climate trouble. Another potential remedy is the search for cleaner fuels that don't emit as much carbon as petrol. Diesel is popular in Europe and slightly less carbon-intensive, though it produces more nitrogen oxide and other grimy particulates. Brazil, meanwhile, has cut vehicle emissions by pumping its cars full of cleaner sugarcane ethanol, but there's not enough sugarcane to fuel the world, at least not without razing rainforests. And ethanol made from corn or soy has been a thoroughgoing fiasco: the ethanol itself likely produces more greenhouse emissions than regular petrol and drives up food prices to boot. Cellulosic ethanol made from indigestible items like corn husks or switchgrass may offer a clean-fuel alternative someday, but no one has made it work yet. Thinking bigger still, car companies have lavished large sums on research into advanced fuel cells, which could theoretically combine, say, hydrogen with oxygen from the air to create electricity. These fuel cells would be virtually emissions-free, but the technical barriers are jaw-dropping, and the cars would require many billions of dollars' worth of infrastructure to transport and store the hydrogen. All of the above is the capsule version of why Gordon and Sperling think electrification is likely to be the backbone of green transport in the medium term. We've already seen hybrid vehicles like the Prius; next up are plug-in hybrids like the much-hyped Chevrolet Volt that hooks up to the grid to charge its battery but still has a combustion engine for backup. After that, perhaps, are full-blown electric cars, which could dramatically reduce emissions - so long as the electricity doesn't come from coal. One downside: it's tricky to set up the infrastructure. Automakers are hesitant to leap into the plug-in market until there are enough recharging stations around for their drivers, while utilities don't want to erect the stations until enough plug-ins hit the road. An impasse like this may require government assistance. Another hurdle: batteries. They're heavy, expensive and still struggle to sustain motor travel over reasonable distances. It's not unreasonable to expect that some mix of technologies might allow the automobile to evolve in such a way that two billion cars can grace the planet without trashing the atmosphere. It's just unclear what incentives, exactly, will bring that future about. Oil supplies may be tightening, but there's likely enough unconventional oil out there - in Alberta's tar sands and Venezuela's heavy-oil reserves - to keep the status quo economically viable for some time without active policy moves. And, as Sperling and Gordon note, an international cap-and-trade regime on carbon emissions, similar to Europe's, won't lift petrol prices enough to revolutionise the auto industry (the cap largely affects utilities and manufacturers, not refineries). Instead, it will take a variety of government policies - everything from petrol taxes to cellulosic ethanol research to fuel-economy standards to electric infrastructure support - all things that are tricky to coordinate across national borders. Just look at the United States, where automakers and the corn lobby have successfully perverted policymaking for their own narrow ends. Happily, China and India appear a tad more far-sighted on transportation policy. Beijing, true, is keener to combat local air pollution than rein in its carbon output, but often the same set of policies can make headway on both problems. That's a good thing, because, as Two Billion Cars makes clear, a sustainable car future isn't just a matter of Europe and the United States inventing fancy new vehicles and then selling them off to poorer nations. China and India have several distinctive transport sectors, such as the millions of three-wheeled "rural vehicles" in the countryside, which will only evolve through home-grown innovation. China, for instance, has a huge market for electric mopeds that can zip in and out of urban traffic; as it advances, the country's electric-moped industry may turn out to be crucial for the future of sustainable transport. That still leaves one other piece: the hard part. Technology alone may not save us; we may have to modify our driving behaviour, too. Sperling and Gordon are curiously dismissive of mass transit as an alternative to the car monoculture, but plenty of research suggests that organising our cities and lives around denser, transit-orientated neighbourhoods (or at least giving people the option of doing so) can cut down on driving, and with it, emissions. It's worth considering, too, other policy tools to reduce the incentive to hop in a car and go, from rush-hour congestion tolls to reducing the amount of free parking available. Trouble is, these measures are politically dicey. Sure, a country like Singapore uses heavy taxes to discourage driving, but one has only to peek at the United States, where a congestion-pricing plan just failed in New York, to see how people bristle at the notion of changing their car-centric behaviour. Nor does careful urban planning always work as expected: leaders in Shanghai have tried hard to avoid Beijing's car-choked fate, restricting car licenses and building new monorail lines, but car use is soaring, and the city's ever-expanding satellite suburbs will cause yet more commuters to buckle up and hit the road. What this means is that adapting to a two-billion-car world will involve not just nifty gizmos and shrewd policy incentives, but also a massive cultural shift - a rethinking of our automotive way of life. That won't come easy. As Ladd's Autophobia shows, writers and thinkers have been dashing off screeds against car dependency for as long as automobiles have prowled the streets. After the Opec oil crisis in the 1970s, magazines and books were littered with huffy obituaries for the car. "Some day America will admit that the automobile is socially and economically obsolete," sniffed one academic in 1980. But the car did not become obsolete, and not just because oil prices cruised back down during the Reagan/Thatcher years or because the auto lobby kept a vise-like grip on lawmakers or because developers tend to actively promote sprawl (though all those things are true). Critics of the automobile had simply underestimated the car's appeal. It's an unbelievably effective way to move about the world and organise our lives. The only way to dampen the automobile's allure is to demonstrate that there is, in fact, an alternate future that's equally efficient and convenient. Two Billion Cars doesn't necessarily have all the answers, but it does show that another way is possible - that our love affair with the automobile doesn't have to be a suicide pact. Bradford Plumer is an editor at The New Republic.