Traffic Nets - Grid Systems

Look back

In history, as well as today, traveling and traffic systems developed naturally, according to geographical, topographical or space-ordering facts. Roads were built to connect settlements or settlements grew along existing roads. Forks or crossings arose where necessary or already existing junctions created new settlements. Cutting a road or traffic usually generated changes in settling and caused movement.
Traffic nets and settlements developed according to traveling speed. Until industrialization process, individual spreading was linked to walking, horse or coach distance, motor mobility starting with the beginning of the 20th century caused the fastest expansion of humans and cities ever. Mobility in the 20th century asked for new concepts in reorganizing travel for entire regions.

While medieval european cities grew radial, many urban environments in modern times (as well as classic forms) were planned, to serve multiple needs. Two famous examples are Barcelona's Eixample and New York's Manhattan. In 1859/60 the catalan engineer Ildefons Cerdà built a quarter in Barcelona called Eixample (expansion) based on equal squares. 1850 he presumed, that every worker would use his own machine for locomotion and straight and wide roads would be needed.
The Manhattan-grid, 1811 was developed by Simeon de Witt, Governor Morris and John Rutherford: they designed a matrix out of 13 x 156 blocks; 2028 estates were planned, inhabitants were still to come, houses had to be built and activities non-existent (Koolhaas).
Manhattan and barcelona, square living was evaluated to be most efficient, economic and space saving.

The „negative“ space surrounding dense built environments is the only space left for transportation. Streets, veins of a city, are inevitable in order to supply and to link quarters and buildings. Crossings act as synapses for exchange of goods and humans. They integrate local areas and entire global networks. But these links evoke congestions and need to be organized. Certain interventions like traffic lights or bridges manage the flow.




In terms to connect greater areas more effective and denser, uniform traffic systems ensure faster traveling with more flexibility. Only two geometric, point-symmetric shapes can build entire modular grids with equal nodes: the square and the equilateral triangle.
Other non-uniform grids such as right-angle triangle or the radial-ring systems in Figure 4 and 5 show irregularities; they vary in node connections and orientation is weak.

In order to keep transportation and mobility high-leveled, continuity in speed and flow must be optimized. Forks and bendings generally reduce speed and flow, and cause congestion. Speed and flow through bendings and forks accumulates with the increment of the angle.
Biophysical veins, such as water flows or tree growth always show obtuse angles. Right and acute angles are unnatural and evoke rebounds. Concretions or strictures in aortas evoke strokes or coronary thrombosis.
To aim a well-balanced traffic flow spread over an entire grid, all vehicles must obtain the same speed. Irregularities in speed and density cause jams and grid locks, loss of energy and pollution.

The square grid (Figure 1) connects with 90 degrees and four directions, the equilateral triangle grid (Figure 2) with 60 degrees and 6 directions. Within the same area the triangle grid provides shorter distances and more connections, but at the same time, more crossings with more collision spots; the square grid crossing merely has to manage 4 directions. Concerning the building space between the rays, the triangle shape shows disadvantages, as the space usage is less efficient.
On the ground only a sex anglegrid, consisting of 6 equilateral triangles, with only 3 oncoming directions would show advantages to the square grid.

In the air the triangle grid shows its strength. By placing the three (including oncoming traffic 6) directions in the air at different height levels, crossings will be dissolved. The junctions of the Skyways run between the main directions and merge to the new path from top or below.
The travel of the acute angles on the triangle grid with 60 degrees can be ignored, because such locomotion would match a reversal and like an unnatural flow behavior it happens as a result of disorientation. Using the 120 degree directions only (Figure 3) the grid shows the same advantages as the square grid (straight, left or right).



Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

zeroG-Autobahnlast updated 09/2006

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