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Sub-problem 1c - Page 3 of 9

ID# C101C03

Sub-problem 1c: Analysis of Future Conditions

Step 2. Results

For the analysis of future conditions, it is often appropriate to select a peak hour factor of 1.0, considering that the projected future volumes, as well as other critical analysis parameters, have a relatively high degree of uncertainty associated with them. In this context, then, using a peak hour factor of 1.0 is equivalent to evaluating the intersection on the basis of the estimated average conditions for the hour rather than the peak 15 minutes. In many cases, the accuracy resulting from this approach is on par with the cumulative accuracy that one can expect for the other critical analysis parameters that must also be estimated.

The value of the arrival type for the signalized intersection option depends on whether the signal will be interconnected with the adjacent intersections and the quality of progression that will be achieved. It is usually conservative to assume random arrivals (Arrival Type 3). The values of the saturation flow rate, the critical gap, and the follow up time depend on local conditions and whether, as volumes increase, driver behavior may change over time. We will assume for this analysis that they remain the same as the original analysis. These are all reasonable assumptions, but most likely the assumptions are less accurate than the estimates we were able to prepare for the existing conditions analysis.

What other factors should be considered? In addition to the factors discussed above, we must also have forecasts of future volume levels. In order that they might be as accurate as possible, future volume projections should not just consider historic patterns of growth but also current local policies regarding development. For example, if growth management policies are in effect, future growth may be lower than historical patterns. And, since we can't know precisely the composition of the traffic stream with respect to vehicle types, it is again usually conservative to assume a passenger car equivalence of 1.1.

For this case study, we are unaware of any land use policies that might change historic growth trends. Since we know that traffic volumes on U.S. 95 are increasing at the rate of 2 percent per year, it is conservative to assume that this rate will continue and that, with compounding, the volumes in ten years will be about 22 percent higher than today's volumes. Click here to see the future traffic volumes.

Let's continue to see the results of the computation.

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