By 1900, rural market zones in Bangkok began developing into residential districts. The Memorial Bridge was constructed in 1932 to connect Thonburi to Bangkok which was believed to promote economic growth and modernization in a period when infrastructure was developing considerably. During the Vietnam War period of the 1960s increased FDI investment flowed into Thailand, improving the Don Mueang airport and its highways.
Since the 1960s modernization and population pressure with now over 8 million people in Bangkok, traffic congestion and pollution has become a significant problem in Bangkok.