Grid Plan - Late 19th Century To The Present

Late 19th Century To The Present

Ildefons Cerdà defined a concept of urban planning, based on the grid, that he applied to the Barcelona Eixample. The Eixample grid introduced innovative design elements that made it exceptional at the time and even unique among subsequent grid plans: a) a very large block measuring 113m by 113m (370 x 370 feet) far larger than the old city blocks and larger than any Roman, Greek blocks and their mutations (see drawing below); b) a 20 m (66 feet) road width (right of way) compared to mostly 3 m in the old city c) square blocks with truncated corners and d) major roads perpendicular and diagonal measuring 50 m (164 feet) in width. These innovations he based on functional grounds: the block size, to enable the creation of a quiet interior open space (60 m by 60 m) and allow ample sunlight and ventilation to its perimeter buildings; the rectilinear geometry, the wide streets and boulevards to sustain high mobility and the truncated corners to facilitate turning of carts and coaches and particularly vehicles on fixed rails.

In maps of larger American cities, mostly east of the Mississippi River, it can be noted that the downtown areas are almost always grids. These areas represent the original land dimensions of the founded city, generally one square mile. Some cities expanded the grid further out from the centre but maps also show that, in general, as the distance from the centre increases a variety of patterns emerge in no particular discernible order. In juxtaposition to the grid they appear random. These new patterns have been systematically classified and their design characteristics measured

In the United States, the grid system was widely used in most major cities and their suburbs until the 1960s. However, during the 1920s, the rapid adoption of the automobile caused a panic among urban planners, who, based on observation, claimed that speeding cars would eventually kill tens of thousands of small children per year. Apparently, at this early stage of the car's entry into the grid, the streets of major cities worldwide were the scene of virtual "slaughter" as the fatality rate per 100,000 pop was more than double the current. In 2009, after several decades of road safety improvements and a constant decline in fatalities, an estimated 33,963 people died in motor vehicle traffic crashes and, according to the National Highway Traffic Safety Administration, "Motor vehicle crashes are the leading cause of death for children from 3 to 14 years old.". Planners, therefore, called for an inwardly focused "superblock" arrangement that minimized through automobile traffic and discouraged it from traveling on anything but arterial roads; traffic generators, such as apartment complexes and shops, would be restricted to the edges of the superblock, along the arterial. This paradigm prevailed between approximately 1930 and 1960, especially in Los Angeles, where notable examples include Leimert Park (an early example) and Panorama City (a late-period one).

A prominent 20th century urbanist, Lewis Mumford, severely criticized some of the grid's characteristics: "With a T-square and a triangle, finally, the municipal engineer could, without the slightest training as either an architect or a sociologist, 'plan' a metropolis, with its standard lots, its standard blocks, its standard street widths, in short, with its standardized comparable, and replaceable parts. The new gridiron plans were spectacular in their inefficiency and waste. By usually failing to discriminate sufficiently between main arteries and residential streets, the first were not made wide enough while the second were usually too wide for purely neighborhood functions . . . as for its contribution to the permanent social functions of the city, the anonymous gridiron plan proved empty."

In the 1960s, traffic engineers and urban planners abandoned the grid virtually wholesale in favor of a "street hierarchy". This is a thoroughly "asymmetric" street arrangement in which a residential subdivision—often surrounded by a noise wall or a security gate—is completely separated from the road network except for one or two connections to arterial roads. In a way, this is a return to medieval styles: as noted in Spiro Kostof's seminal history of urban design, The City Shaped, there is a strong resemblance between the street arrangements of modern American suburbs and those of medieval Arab and Moorish cities. In each case, the community unit at hand—the clan or extended family in the Muslim world, the economically homogeneous subdivision in modern suburbia—isolates itself from the larger urban scene by using dead ends and culs-de-sac.