Civil Engineering Reference
In-Depth Information
stations are shown in Figure 13; transit is not shown because it was so similar
to refuse that it obscured the curves.
Figure 13 reveals the effects of changing the station cost, such as:
•
The influences of increasing/decreasing 50% are symmetrical.
Increasing the station cost 50% has an equal and opposite effect on
payback years as decreasing it 50%.
•
The school bus fleet is much more sensitive to changes in station cost
than the other fleets. A 50% reduction in cost reduces payback by 4.9
years in a 75-bus fleet and 1.7 years in a 300-bus fleet.
•
In the refuse fleet, a 50% reduction in cost reduces the payback period
by less than a year if the fleet is over 100 buses. It can make up to a 4-
year difference in very small (20- truck) fleets.
Figure 13. Payback period by station cost.
What Happens As My Vehicle Incremental Cost Changes?
There is a distinct possibility that manufacturing efficiencies will decrease
the cost of a CNG vehicle or that 2010 emissions requirements will increase
the cost of a diesel vehicle. Either of these events would reduce the
incremental cost of a CNG vehicle (over a diesel vehicle). There is also a
possibility that the CNG vehicle purchased by your fleet has a higher
incremental cost than the averages used in the base case. To explore the impact
of these scenarios on project profitability, NREL modeled one case where the
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