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Analysis - Page 2 of 2 |
ID# C1010A2 |
Problem 1: Analysis of the U.S. 95/Styner-Lauder Avenue
Intersection
Exhibit 1-19. Summary comparison of average control delay estimates (sec/veh) |
Movement |
Existing volumes |
Future volumes |
TWSC |
Signal control |
TWSC |
Signal control |
EB LT |
47.0 |
19.1 |
297.5 |
21.2 |
EB TH/RT |
25.3 |
20.7 |
55.7 |
22.0 |
WB LT |
36.0 |
18.9 |
134.4 |
19.7 |
WB TH/RT |
27.6 |
22.9 |
80.9 |
25.3 |
NB LT |
8.6 |
5.7 |
9.1 |
5.9 |
NB TH/RT |
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6.1 |
|
6.3 |
SB LT |
8.3 |
5.9 |
8.6 |
6.2 |
SB TH/RT |
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6.6 |
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6.9 |
A review of the information contained in Exhibit 1-19 provides important information to
think about as the decision to signalize the intersection (or not) is
considered:
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Drivers on U.S. 95 will experience some delay if signal
control is added to the intersection, though the delay is minor (between 6
and 7 seconds per vehicle). However, more costly than this delay is the
fact that some portion of the drivers on these approaches will have to
stop, something that might be viewed as a degradation of service by many
drivers. |
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This reallocation of delay, however, significantly
improves the operations of the Styner (westbound) and Lauder (eastbound)
approaches. For example, drivers will experience a slight improvement in
their level of service (with average delay reduced from 27.6 seconds to
22.9 seconds) if the intersection is signalized with existing volumes.
Considering operations with future volumes, this change is much more
dramatic, with delay being reduced from 80.9 seconds to 25.3 seconds. |
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It is also important to point out that we should
consider that the off peak period constitutes 80 to 90 percent of the
total time that an intersection operates. During these times when volumes
are often significantly lower than in the peak period, a traffic
signal can sometimes be less efficient than stop-sign control. Or, a
signal may not even be necessary during these time periods! This is why
other forms of control (such as roundabouts) or flashing signals are
sometimes considered during off-peak periods. |
| Other options might also be available to avoid
signalizing the intersection. If, for example, the signalized
intersections on either side of the Styner/Lauder intersection are
coordinated and timed in such a way as to create regular gaps in the
traffic stream on U.S. 95, then the TWSC intersection analysis might yield
much more acceptable results when these effects are taken into account.
This may or may not be a practical option, but is something that should be
considered so that decision makers are presented with the fullest-possible
range of viable options. |
The information presented here indicates that changing
from TWSC to signal control will improve the operation of this intersection,
particularly over the next ten years. The uncertainty analysis that we
conducted as part of
sub-problem 1c
confirms that this decision is a sound one.
Discussion:
But have we considered all
relevant factors in this analysis? Take a few minutes to identify other
factors that you think should be considered in this analysis, and continue
to the next page when you are ready.
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