Sub-problem 2a - Page 1 of 2 |
ID# C202A01 |
Sub-problem 2a: Moe Road AM
peak hour - Existing Conditions
Pedestrians
Pedestrians, who must be taken into account during intersection analyses,
have very different needs from those of the vehicles. Pedestrians have
conflicts with the right-turning vehicles, they sometimes need an all-walk
phase with no vehicular movements, and they need very different signal
timings.
We will start our analysis with the signal timings. To cross the intersection, regardless of
direction, the pedestrians always need two to three times as much time as
the vehicles do. In fact, the pedestrian times tend to be distributed
exactly opposite to the vehicle times. For the vehicles, the largest
green time is usually needed for the main street and much less time is needed
for the side street. It’s the other way around for pedestrians, where the
street widths dictate the green times, not the pedestrian volumes. Most
often, the street that’s widest to cross is the main street. And since
the pedestrians cross the main street concurrent with the side street throughs-and-rights,
the side street green time is boosted considerably. Similarly, the
pedestrian times for the main street are much shorter than the vehicular
times because the width of the side street is typically less.
In an
intersection where vehicular greens are 30 seconds for the main street and
10 seconds for the side street, pedestrian timings need to be quite
different. The pedestrian greens might be 20 seconds for the main street
(7 seconds of walk plus 13 seconds of flashing don’t walk, based on a
40-foot wide street) and 28 seconds for the side street (7 seconds of walk
plus 21 seconds of flashing don’t walk, based on a 70-foot wide street).
In this situation, the usual solution is to boost the vehicular signal
timings so that 1) the 24-second minimum for the side street is met, and
2) the 30:10 ratio for the vehicular times still pertains. Thus, the main
street green would have to be 72 seconds to satisfy the 30:10 ratio, given
the 24-second green on the side street. Assuming 4 seconds for the yellow
and all red, the 48-second cycle without the pedestrians (30+4+10+4)
becomes a 104-second cycle with pedestrians (72+4+24+4).
At Moe
Road, pedestrians are important during the AM Peak hour. Students cross
Route 146 going south on their way to school. Consequently, for an AM peak
hour analysis, we have to take into account the pedestrians on the
north-south phase.
Discussion:
This
is the only time pedestrians are considered in the Clifton Park case study.
Think about intersections in which you have had to
take pedestrians into account. What did you learn? What were the constraints
the pedestrians imposed? How often are they given appropriate
treatment? At this intersection, or one with which you are familiar, what
kinds of design features need to be incorporated to ensure the pedestrians
are appropriately accommodated?
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