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.