Cities all over the world are fighting against smog. A German court has ruled that cities are allowed to impose driving bans. Many German cities — including Stuttgart, shown here — have developed an air pollution problem and are debating how best to approach the problem.

A diesel ban is imposed in the Norwegian capital whenever air pollution levels rise above a prescribed limit. The ban went into effect for the first time on January 17, 2017. Ambulances and other public service vehicles running on diesel are exempt from the measure. The city plans to reduce even more cars by eliminating municipal parking spaces in the center starting in 2019.

Starting in 2024, the French capital will ban diesel vehicles; in 2030 it intends to expand the ban to gas-powered cars. Vehicles manufactured before 1997 are already prohibited in the city on weekdays. When air pollution levels exceed prescribed limits, Parisians have to follow a rotation system in which only cars with either even- or odd-numbered plates are allowed to be driven in the city.

If you want to drive into the center of London, a day's ride through the city will cost you 10 pounds ($13.80, €11.20). London introduced the congestion charge in 2003. Automatic number plate recognition is used to enforce the measures. Anyone who does not pay the fee faces a heavy fine of up to 240 pounds.

Copenhagen's mayor, Frank Jensen, wants to prevent new diesel cars from entering the city starting in 2019. Currently, over 300 kilometers of roads in the Danish capital can only be used by cyclists. With the new regulations, cycling will become easier, more convenient and cheaper than driving a car. About half of Copenhageners now cycle to work.

Car-free zones like the square in front of Madrid's Teatro Real are set to become a common sight in the city. Almost the entire center of the Spanish capital will be turned into pedestrian zones in the next five years. Madrid has high smog levels, due to being surrounded by mountains, which cause bad air to get trapped in the city.

Riding public transport will become even easier in the near future in Helsinki. In the next ten years, a mobility on demand system will be developed to include all forms of public transport in one app, including buses, self-driving cars and minibuses with flexible routes. The goal of the app is to be so good that no one will want to own a car.

Smog chokes Delhi and levels of air pollution regularly go off the scale. Electric rickshaws will hopefully alleviate the problem. By 2030, all new vehicles will be electrically powered and the city will phase out gas powered vehicles.

About two weeks after Volkswagen admitted behind closed doors to US environmental regulators that it had installed cheating software in some 11 million of its diesel vehicles worldwide, the Environmental Protection Agency shared that information with the public. It was September 18, 2015. The ensuing crisis would eventually take a few unexpected turns.

Volkswagen's then-CEO Martin Winterkorn (above) had little choice but to step down several days after news of the scandal broke. In September 2015, he tendered his resignation, but retained his other posts within the Volkswagen Group. Winterkorn's successor was Matthias Müller. Until taking the reins at VW, Müller had been the chairman at Porsche, a VW subsidiary.

Regulators in the US weren't the only ones investigating VW. Authorities in Lower Saxony, the German state in which VW is based, were also scrutinizing the company. On October 8 2015, state prosecutors raided VW's headquarters along with several other corporate locations.

On January 4, 2016, the US government filed a lawsuit against VW in Detroit, accusing the German automaker of fraud and violations of American climate protection regulations. The lawsuit sought up to $46 billion for violations of the Clean Air Act.

In March 2016, the head of VW in the US, Michael Horn, resigned. In the initial days and weeks after the scandal broke, he was the one US authorities turned to for information. He issued an official apology on behalf of the automaker, asking for the public's forgiveness.

On October 25 2016, a US judge approved a final settlement that would have VW pay $15.3 billion. In addition, affected cars would be retrofitted with better, non-deceptive hardware and software, or else VW would buy them back completely from customers.

When dieselgate first emerged in 2015, analysts said it was likely other car makers were also cheating tests. But it wasn't until 2017 that other companies were targeted in probes. In July, German authorities launched investigations into luxury car makers Porsche and Daimler for allegedly cheating emissions tests. Others, such as Audi and Chrysler, have also been hit by similar allegations.

Despite dieselgate, VW has managed to keep the emissions scandal from utterly tarnishing its image. According to several polls, between 55 to 67 percent of Germans continue to trust the automaker. In the US, polls show that roughly 50 percent still believe the German company produces worthwhile vehicles.

In late January, however, VW suffered another heavy blow over reports that the company experimented on monkeys and made the animals inhale diesel fumes. To make matters worse, a separate experiment that had humans inhale relatively harmless nitrogen dioxide was revealed at the same time. Some media wrongly interpreted this to mean humans were also inhaling toxic fumes.

Years after the scandal that caused Volkswagen to pay CAN$2.4 billion (US$1.83 billion), a court in Toronto order a further fine of CAN$196.5 million. Volkswagen pleaded guilty of violating in environmental laws. Prosecutor Tom Lemon noted that the fine was "26 times the highest fine ever for a Canadian environmental offence."