In a diverging double crossover diamond interchange, what volume of
traffic creates a need for stoplights? Where there is a low volume of
cross traffic, it seems sufficient to require vehicles entering the
crossover to yield to those exiting the crossover, and those on the
ramps to yield to everyone. (On the other hand, if there is little
traffic on the ramps, why fork them?)
With hatched zebra crosswalks after the two yield signs on the cross
road, pedestrians would be able to walk diagonally across the
interchange, via the center median. With proximate signalized
intersections (or well-marked hatched zebra crosswalks) on either side
of the interchange, pedestrians could cross the road to reach the
other two corners. (If unhatched ordinary crosswalks are used for this purpose, they leave no marking available for crosswalks designed only
to make sure the pedestrian crosses in the right place and does not
wander across a lane of moving traffic.)
Is there a design for a double crossover using two quadrants? It might
be used where a surface road rises to cross another surface road and
an adjacent non-roadway transportation corridor (railroad or canal),
with insufficient space between the lower road and the non-roadway.
Both roads would crossover. The ramps would have some resemblance to cloverleaf ramps that merge together for most of their length, except
that they would be one-way, not two-way, and would thus lack the usual
double yellow line. One ramp would carry all upward traffic, the other
all downward traffic. If the lower roadway was reflected by another on
the far side of the bridge, the traffic could travel on the left for
the entire length of the bridge before crossing back. Restricting
heavy vehicles to the right lane crossing the bridge could minimize
torsion (as caused by subway trains passing on the sides of the
Williamsburgh Bridge instead of down the middle).
-- Buster <http://www.rev.net/~aloe/transportation>
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