Traffic Congestion
When the government realised they needed to dramatically improve Seoul's traffic, they came up with a plan to greatly improve the congestion. Creating more roads/lanes would not help the situation as studies show that new roads brings new drivers and the congestion stays roughly the same. So the answer: develop a new public transport system! The Seoul subway is said to be one of the best in the world. The government is strongly encouraging more people to ride, walk or use public transport. One way of doing so is by planning to create a public bike service throughout Seoul, that's free of charge. By 2030, the government hopes to create a city with such a highly convenient transport system, people won't even need to rely on cars.
Air pollution
Seoul's main leading cause of air pollution is from automoblies and traffic congestion. We already know some ways to stop traffic congestion and reduce pollution, but what about some other ways. In September 2014, Seoul, and other cities experiencing pollution issues like Shanghai and Hong Kong, gathered and presented their goals for reducing fine air particles. Seoul has declared to reduce 20% of its current PM2.5 (fine particle matter smaller than 2.5 microns) by 2018. They plan to do this by controlling ultra-fine dust and nitrogen dioxide particles in the air and operating 'green cars' and promoting eco-friendly driving.
Water Pollution
In an effort to reduce water pollution, the Korean government has done a project called the 'Four Major River Restoration', a multi-purpose project on the Han, Nakong, Guem and Yeongsan rivers. The project's aim was to secure any abundant resources of water, improve water quality, restore the ecosystems of the river and also make green parks around the areas to increase the use of waterways. The results have proven to be effective and proves that South Korea (Seoul) is taking global leadership in facing these challenges.
Cheonggyecheon Stream
The Cheonggyecheon stream is a fantastic example of solving all three problems. It is a 10.9 km stream flowing through down-town Seoul, which flows into the Han River. In 1968, an elevated highway was built on top of it. In 2003, Lee Myung-Bak proposed to remove the highway and help restore the stream and turn into a park. Once open to the public in 2005, it was proved to be a magnificent solution to many problems. The government created a series of subways and buses near the park, greatly reducing traffic congestion in the area, which also reduced air pollution. It also began to flow more water into the Han River, which helped to reduce water pollution. The park also managed to stop the divide between the north and south sides of the city, bringing the city together.