|
Here's
a city with only two ranks of roadway: expressways and
streets. Roadways shown in blue are elevated ten feet above the
general terrain, while pink ones are depressed ten feet below.
The
intersection at the upper left involves four one-way
expressways: southbound First and northbound Second in blue,
and westbound Camel and eastbound Dove in pink. This
intersection is essentially the crossing of two freeways. In
the "medians" of the "freeways," each yellow
block is an office tower with a garage on the lower few levels.
Traveling
north on Second, you can turn right onto Dove by means of a
descending ramp. (However, to make a left turn onto Camel,
you'd have to drive a block farther and then go around the block by
making three rights.)
Alternatively,
partway down that descending ramp from Second you can make a sharper
right turn into the small local street system consisting of an X
superimposed onto two octagonal rings.
(TEXT
CONTINUED BELOW)

From
the outer ring, ascending or descending ramps lead drivers across
the expressway lanes to the garages of each of the eight surrounding
office towers. Pedestrians on the pink level can pass under all
the roadways and access the towers, except at the top of the drawing,
where they must climb to the blue level to pass over the Camel/Dove "freeway." |