Subproblem 1c  Page 7 of 9 
ID# C101C07 
Subproblem 1c: Analysis of
Future
Conditions
Uncertainty
analysis is often used to consider the effects that uncertainty in the input
values for a problem will have on the outputs, and whether these effects
will be significant. To illustrate this kind of analysis, we will consider
three cases. The first case is the base case,
where we assume that the volumes that we used are correct. The second case
assumes that our volume forecasts are high by 25 percent, while
the third case assumes that the volume forecasts are low by 25 percent.
Exhibit 114 focuses exclusively on a single performance measure (average
control delay), though in reality we would also want to explore the impact
on other performance measures such as v/c ratio and queue length.
Exhibit
114. Comparison of Average Control delays
(sec/veh) (Datasets) 
Movement 
TWSC 
Signal
control 
Base case 
Volumes +25% 
Volumes
25% 
Base case 
Volumes
+25% 
Volumes
25% 
NB LT 
9.1 
9.8 
8.5 
5.9 
6.6 
5.6 
NB TH/RT 



6.3 
6.7 
6.0 
SB LT 
8.6 
9.1 
8.1 
6.2 
6.9 
5.8 
SB TH/RT 



6.9 
7.6 
6.4 
EB LT 
297.5 
 
34.1 
20.4 
24.8 
18.6 
EB TH/RT 
55.7 
305.2 
20.9 
22.0 
24.2 
20.3 
WB LT 
134.4 
 
27.6 
19.6 
21.8 
18.6 
WB TH/RT 
80.9 
443.9 
22.0 
25.3 
30.6 
22.1 
Exhibit 114 shows two very interesting points. First,
for the minor movements at the TWSC intersection, the volume changes have a
large impact on the final results. This shows that the projected
operation of the intersection is unstable to begin with, and that any
increase in the volumes will further degrade the intersection performance.
Second, we can have some degree of confidence that, under signal control,
the intersection will perform as planned, even if we are somewhat uncertain
about the input volumes that we've projected. These results can help
decisionmakers feel more certain about the range of possible ramifications
associated with different control decisions.
In addition to varying the input volumes, we could also
determine the sensitivity of other input or default values on the final results. For example, the critical gap, the follow up time, the saturation flow rate, and
the arrival type are all important parameters in the computation of capacity
and delay. The base case values for these parameters could also be varied
to determine their effect on the final results.
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