Some 385,000 people worldwide died prematurely in 2015 from air pollution caused by vehicle exhaust emissions, a US study has found, singling out diesel engines as the main culprit.
President Donald Trump says the US may impose car tariffs on the European Union's products if the two sides are unable to reach a deal.
France has reduced its speed limit on two-lane highways to 80 kilometres per hour (50 mph), putting it in the European slow lane with one of the lowest rates across the continent.
US President Trump's threat to tax imported cars in the name of national security risks weakening domestic manufacturers, but could accelerate renegotiation of the North American Free Trade Agreement.
Within the space of 15 years self-driving cars will probably be a common sight on roads. This means robot cars will have to act in potentially life-threatening situations. Scientists are teaching the machines to make complex decisions in an emergency. The graphic illustrates how a self-driving car works.