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Once a Federal agency has identified its most important mobile greenhouse gas (GHG) emission sources overall, it can work with individual sites to determine vehicle usage and refueling trends. Agencies can compare the results of this analysis to internal standards and requirements to identify GHG mitigation opportunities for assets that are underperforming or underutilized. Two examples of this type of analysis focus on:
|Figure 1. Proportion of petroleum and alternative fuel used in Agency ABC flex-fuel vehicles|
Alternative Fuel Consumption
An agency can use fleet and fuel consumption data to determine the extent to which vehicles are utilizing alternative fuel. Many Federal fleets contain flex- or dual-fuel vehicles, which are capable of using gasoline or an alternative fuel such as E85 or compressed natural gas (CNG). Under the Energy Independence and Security Act (EISA) of 2007, dual-fueled, alternative fuel vehicles (AFVs) are required to use alternative fuel unless they receive a waiver, which is only given if the vehicle is located greater than 5 miles from an alternative fueling station or if the alternative fuel is unreasonably more expensive than gasoline.
If vehicle-specific fuel consumption is available, sites can see how much petroleum versus flex-fuel AFVs are using. In the following example, Agency ABC has a fleet located in Cincinnati, Ohio. The fleet contains several E85 and CNG flex-fuel vehicles. Using fuel purchase receipts, the fleet manager at this location is able to determine the relative levels of gasoline and alternative fuel its flex-fuel vehicles are using, as shown in Figure 1.
In this fleet, E85 flex-fuel vehicles are primarily using E85 instead of gasoline. However, CNG dual-fueled vehicles are using more gasoline than CNG. The fleet manager now focuses data analysis on why drivers are not refueling with CNG. Using the Alternative Fueling Station Locator, the fleet manager looks for CNG and E85 refueling stations within five miles of the fleet garage (see Figure 2). No CNG fueling stations and one E85 fueling station are present within this radius. Thus, E85 vehicles have convenient access to fuel, but CNG vehicles do not.
|Figure 2. Alternative fueling stations within a five mile radius of Cincinnati fleet location|
This analysis might lead the Agency's Cincinnati fleet manager to work with headquarters to reallocate CNG vehicles from this site and place them at other agency garages that are located near CNG refueling stations. This data can also be used to help Agency ABC decide whether to install its own alternative fuel infrastructure at this site-if the CNG demand were very high, the agency should evaluate the costs and benefits of installing its own pump.
In addition to analyzing data on alternative fuel consumption, vehicle managers can also assess vehicle usage, which is one of the most useful data elements for GHG mitigation planning. Not currently collected through required fleet reporting, these data are most useful at the vehicle-specific level.
|Figure 3 shows an example vehicle utilization analysis for a fleet in Agency ABC.
Two utilization metrics are presented here: 1) the number of hours per day that
each vehicle is in use; and 2) the user-to-vehicle ratio. The higher either of these
numbers are, the greater the vehicle's utilization.
In an effort maximize vehicle utilization, agency or vehicle managers may choose to establish a standard or threshold for utilization. For vehicles with lower usage, fleet managers can look at opportunities for vehicle sharing across departments and possibly eliminating under-utilized vehicles from their inventories.
For instance, as illustrated in Figure 3, a certain site in Agency ABC has established a utilization goal of 5 hours per day per vehicle. The vehicle manager might investigate whether the finance and human resources units could share a vehicle to eliminate either Vehicle 002 or 003, which are underutilized relative to the agency's goal. The site can reduce its GHG emissions by using an efficient or AFV to accommodate the needs of these two departments.
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