information:classification, information:filtering, structural:expansion
Roads

Road-based transport is the primary mode of travel in Bangkok. Due to the city's organic development, its streets do not follow an organized grid structure. Forty-eight major roads link the different areas of the city, branching into smaller streets and lanes (soi) which serve local neighbourhoods. Eleven bridges over the Chao Phraya link the two sides of the city, while several expressway and motorway routes bring traffic into and out of the city centre and link with nearby provinces. The first expressway in Bangkok is Chaloem Maha Nakhon Expressway, which opened 1981.

Bangkok's rapid growth in the 1980s resulted in sharp increases in vehicle ownership and traffic demand, which have since continued—in 2006 there were 3,943,211 in-use vehicles in Bangkok, of which 37.6 per cent were private cars and 32.9 per cent were motorcycles. These increases, in the face of limited carrying capacity, caused severe traffic congestion evident by the early 1990s. The extent of the problem is such that the Thai Traffic Police has a unit of officers trained in basic midwifery in order to assist deliveries which do not reach hospital in time. While Bangkok's limited road surface area (8 per cent, compared to 20–30 per cent in most Western cities) is often cited as a major cause of its traffic jams, other factors, including high vehicle ownership rate relative to income level, inadequate public transport systems, and lack of transportation demand management, also play a role. Efforts to alleviate the problem have included the construction of intersection bypasses and an extensive system of elevated highways, as well as the creation of several new rapid transit systems. The city's overall traffic conditions, however, remain poor.

Traffic has been the main source of air pollution in Bangkok, which reached serious levels in the 1990s. But efforts to improve air quality by improving fuel quality and enforcing emission standards, among others, had visibly ameliorated the problem by the 2000s. Atmospheric particulate matter levels dropped from 81 micrograms per cubic metre in 1997 to 43 in 2007. However, increasing vehicle numbers and a lack of continued pollution-control efforts threatens a reversal of the past success. In January–February 2018, weather conditions caused bouts of haze to cover the city, with particulate matter under 2.5 micrometres (PM) rising to unhealthy levels for several days on end.

Although the BMA has created thirty signed bicycle routes along several roads totalling 230 kilometres (140 mi), cycling is still largely impractical, especially in the city centre. Most of these bicycle lanes share the pavement with pedestrians. Poor surface maintenance, encroachment by hawkers and street vendors, and a hostile environment for cyclists and pedestrians, make cycling and walking unpopular methods of getting around in Bangkok.