Street hierarchy: Difference between revisions

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Revision as of 14:19, 4 September 2024

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In the pre-automotive era of cities, traces of the concept of a hierarchy of streets in a network appear in Greek and subsequent Roman town plans. The main feature of their classification is their size. In Roman cities, such as [[Pompeii]], major thoroughfares (e.g. the [[Decumanus Maximus|decumanus]]) had a width of 12.2 m, secondary streets (e.g. the [[cardo]]) 6 m and tertiary streets (e.g. vicinae) measured 4.5 meters. The first allowed for two way cart traffic, the second generally only one, while the third only loaded animals. Narrower streets that could only accommodate pedestrians were also present in both Greek and Roman cities. Thus the restriction on connections between major streets on particular modes (carts and chariots) was the effect of the width of the street itself and not the lack of linkage. This method is akin to the contemporary concept of [[permeability (spatial and transport planning)|filtered permeability]].

A clearer record of a stricter hierarchical order of streets appears in surviving and functioning Arabic-Islamic cities that originate in the late first millennium AD such as the [[Medina of Tunis]], [[Marrakesh]], [[Fes el Bali|Fez]], and [[Damascus]]. In theseThese cases there arefeature four classes of streets starting with the cul-de-sac type (1.84-2.00 m wide) and moving up to the local (third order connector), then a collector that usually surrounds a residential quarter (second order connector) and, finally, to the first order connector (arterial). The latter connector usually crossed the city through its centre and led to the city gates (see drawing). These arterials were decreed to be at least wide enough for two crossing loaded animals, 3.23 to 3.5 m.<ref>Besim Hakim 1986, Arabic-Islamic Cities – Building and Planning Principles KPI Ltd, London</ref> This tendency for hierarchical organization of streets was so pervasive in the Arab-Islamic tradition that even cities that were laid out on a uniform grid by Greeks or Romans, were transformed by their subsequent Islamic conquerors and residents, as in the case of Damascus.<ref>Nezar Alsayyad, 1991 Cities and Caliphs: on the Genesis of Arab Muslim Urbanism, Greenwood Press</ref>

In the automotive 20th century, the street hierarchy concept was first elaborated by [[Ludwig Hilberseimer]], in his ''City Plan'' of 1927. His major priorities were increasing the safety of [[primary school]]-age children [[walk to school campaign|walking to school]], and increasing the speed of traffic.