FLEET Model Tutorial
Inputs Area:
From the Inputs Area, you will be able to set several variables that describe the overall vehicle fleet, including the total number of vehicles in the fleet ('Total Light Duty Vehicle Stock'), the average miles traveled each year by each vehicle in the fleet ('Vehicle Miles Traveled/Vehicle') and the average fuel economy of the baseline vehicle in the fleet (i.e. the most common vehicle in the fleet - 'Baseline Fuel Economy').
As can be seen above, FLEET models values for the years 2005-2030.
In this Tutorial, we will be approximating the light duty vehicle fleet of the entire United States.
Note: 'light duty vehicles' refers to passenger cars, vans, SUVs and light trucks. Medium and heavy commercial trucks and vans are not light duty vehicles and are not modeled by FLEET.
To begin, we will set the total size of the vehicle fleet by following these steps:
1. In the 'Initial Year' input box for the 'Total Light Duty Vehicle Stock' row, input the value '2005'. This indicates that the value we'll input next in 'Initial Value' input box corresponds to the number of light duty vehicles on the road in the year 2005.
2. In the 'Initial Value' input box for the 'Total Light Duty Vehicle Stock' row, input the value '250'. There were roughly 250 million light duty vehicles on the road in the United States in 2005.
3. In the 'Annual Growth Rate' input box for the 'Total Light Duty Vehicle Stock' row, input the value '2'. The size of the U.S. light duty vehicle fleet grows at a rate of roughly 2% per year. After inputting this value, click the 'Set Inputs' button. Clicking the 'Set Inputs' button tells the FLEET model that you have updated input values and forces it to recalculate outputs. You will now see values appear for the six text boxes in the 'Total Light Duty Vehicle Stock' row that correspond to the years 2005, 2010, 2015, 2020, 2025 and 2030.
These values are calculated by assuming the size of the fleet grows exponentially using the inputs we set above (i.e. growing at a 2% annual growth rate from an initial value of 250 million vehicles in the year 2005). As you can see, given these inputs, there will be 410.15 million light duty vehicles on the road in the United States by 2030.
Note: As can be seen here, FLEET displays values out to two decimal points. User-inputted values may have a higher degree of accuracy, but model outputs will always be rounded to two decimal points, and FLEET will not provide a higher degree of accuracy than that.
You will also see the Graph/Table Area update and display a graphical representation of the total vehicle stock. The Graph/Table Area automatically updates when you change input variables (usually after you click the relevant 'Set Inputs' button).
We will now set the average miles traveled per vehicle in the vehicle fleet each year using the following steps:
1. In the 'Initial Year' input box for the 'Vehicle Miles Traveled/Year' row, input the value '2005'. This indicates that the value we'll input next in 'Initial Value' input box corresponds to the average annual vehicle miles traveled per vehicle in the year 2005.
2. In the 'Initial Value' input box for the 'Vehicle Miles Traveled/Year' row, input the value '10,000'. The average U.S. light duty vehicle travels 10,000 miles per year.
Note: FLEET allows user input values to include commas. The use of commas is optional, and FLEET will strip them out when calculating values. FLEET will display outputs using commas to separate every three digits.
3. In the 'Annual Growth Rate' input box for the 'Vehicle Miles Traveled/Year' row, input the value '.25'. The average miles traveled per vehicle in the United States increases at a rate of roughly .25% per year. After inputting this value, click the 'Set Inputs' button. You will now see values appear for the six text boxes in the 'Vehicle Miles Traveled/Year' row that correspond to the years 2005, 2010, 2015, 2020, 2025 and 2030.
Note: When inputted a decimal number, a '0' before the decimal point is optional. Thus, an input of '0.25' will be treated the same as an input of '.25' by FLEET. FLEET will display outputs with a '0' preceding any decimal values.
Lastly, we'll set the average fuel economy of the baseline vehicle in the U.S. light duty vehicle fleet. The 'baseline vehicle' refers to the most common type of vehicle in the fleet. In the case of the U.S. light duty fleet, the most common vehicle is a conventional spark-ignition gasoline-fueled vehicle. In FLEET, you can specify the 'baseline vehicle' using the Pathways Selection Area, which we will do shortly. For now, we'll set the average fuel economy of the baseline vehicle using these steps:
1.We could set the baseline fuel economy by following the same steps we did above - setting the initial year, initial value and annual growth rate, and then letting FLEET extrapolate values using an exponential growth formula. However, FLEET also offers the option to input values for key years - every five year increment - manually. To do so, click the 'manual input?' check box located below the 'Baseline Fuel Economy' label.
As you can see, clicking the 'manual input?' check box toggles between exponential growth input and manual input modes. The exponential growth input fields ('Initial Year', 'Initial Value' and 'Annual Growth Rate') are now no longer input boxes while the '2005', '2010', '2015' etc. text fields are now input boxes, allowing us to manually input values for each of these key years. FLEET will interpolate annual values for the years between these key years (using an exponential growth rate), but the manual input mode allows the user to model different growth rates other than a standard exponential growth curve.
2. In '2005' input box for the 'Baseline Fuel Economy' row, input the value '20'. The average fuel economy of the U.S. light duty fleet is roughly 20 miles per gallon.
3. In each of the other year input boxes, input the following values: '2010' = '21', '2015' = '22', '2020' = '23', '2025' = '24' and '2030' = '25'. That is, we're assuming that the average fuel economy of conventional gasoline-fueled vehicles in the United States increases at a rate of 1 miles per gallon every five years. When you are done, click the 'Set Inputs' button one more time.
Note: the 'Baseline Fuel Economy' values in FLEET refer to the average fuel economy of all baseline vehicles on the road in a given year. This will differ from the average fuel economy of new vehicles sold in any given year, as the vehicle stock on the road includes older vehicles as well as new vehicles. The 'Baseline Fuel Economy' value should not be the same as Corporate Average Fuel Economy regulations, for example, or other assumptions about the fuel economy of new vehicles sold in a given year. If fuel economy standards for new vehicles increase over the years, the average fuel economy of the vehicle stock will also improve, but will lag behind the fuel economy of new vehicles as older vehicles are slowly replaced by newly purchased vehicles over time.
We've now set all the inputs in the Inputs Area.
We've specified that we're modeling a vehicle fleet that begins with 250 million vehicles in 2005 and grows at a rate of 2% per year to 410.15 million vehicles in 2030. We've specified that each vehicle in the fleet travels an average of 10,000 miles per year in 2005 and that the total vehicle miles traveled per vehicle increases at .25% per year to 10,644.11 miles per vehicle per year by 2030. Finally, we've specified that the average fuel economy of a conventional gasoline vehicle - the baseline vehicle - is 20 mpg in 2005 and increases by 1 mpg every five years to 25 mpg by 2030.
Next we'll specify the composition of the vehicle fleet using the Pathways Selection Area.
To continue the Tutorial, click here.
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