Conditions and Performance
Chapter Listing
Conditions and
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Introduction
Highway Sensitivity Analysis
Transit Sensitivity
Analysis
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Transit Sensitivity Analysis
One of the most important parameters used by TERM in forecasting transit investment needs is
the projected growth rate in transit passenger miles traveled (PMT). This forecast is obtained
from metropolitan planning organizations (MPOs) in large urbanized areas, most of which make
forecasts about transit PMT and auto VMT growth as part of the regional transportation planning process.
The average annual growth rate in PMT from the most recently available MPO forecasts, used in
this report, is 1.90 percent.
The assumed passenger travel growth rate has several important effects on the estimates of
investment requirements. The effect is most important for Asset Expansion. The forecast travel growth
rate is the primary factor in determining the need for system expansion in order to
accommodate increased transit usage while maintaining a constant degree of vehicle utilization. A larger
growth rate also affects the degree to which crowded systems become even more so, requiring even
more investment to achieve Performance Improvement. On the other hand, the growth rate does not
affect the need for the replacement and rehabilitation of the existing capital stock as it wears out.
In order to examine the sensitivity of the estimated transit investment requirements to forecast
transit growth rates, TERM was run using the following three alternative scenarios:
1) PMT growth is 50 percent greater than the forecast levels
2) PMT growth is 50 percent less than the forecast levels
3) There is no growth in transit PMT.
The effect of varying the growth rate is shown in Exhibit 10-3. Adjusting the growth rate has
a significant effect on the estimated investment requirements, though the effect is greater under
the Maintain Conditions and Performance scenario. Under the Maintain scenario, each 1
percent change in the growth rate causes a 35 to 40 percent change in investment requirements, while
the same change in the growth rate changes the Improve scenario investment requirements by 25
to 30 percent. The smaller sensitivity under the Improve scenario is due to the greater replacement
and rehabilitation expenditures which are necessary for condition improvements. Note that even
under conditions of no growth in passenger miles, major investment would still be required in order
to maintain the current system, with still greater expenditures to improve conditions and
performance relative to current levels.
Exhibit 10-3. Impact of Alternative PMT Growth Rates on Transit Investment Requirements
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