The Transportation Revenue Estimator
and Needs Determination System (TRENDS) Model
Developed by the Texas Transportation Institute
and the
Texas Department of Transportation
Jessica Castiglione, P.E.
Texas Department of Transportation
Project Supervisor
David R. Ellis, Ph.D.
Texas Transportation Institute
Research Scientist
The TRENDS Model is designed to provide transportation planners, policy makers and the public with a tool to forecast revenues and expenses for the Texas Department of Transportation (TxDOT) for the period 2010 through 2035. The User, through interactive windows, can control a number of variables related to assumptions regarding statewide transportation needs, population growth rates, fuel efficiency, inflation rates, taxes, fees and other elements. The output is a set of tables and graphs showing a forecast of revenues, expenditures and fund balances for each year of the analysis period.
TRENDS will be updated on a monthly basis to include the latest cash forecasts and letting schedules from TxDOT. In addition, as updates regarding population forecasts, inflation rates, fuel efficiency, and other variables become available, they will be incorporated into the model.
This paper will take the User through the model and its basic calculations by describing each of the tabs at the bottom of the Excel spreadsheet. Then, there will be a brief description of the calculations on each tab and a description of the “Data Input and Summary” tab where the results are presented.
Table of Contents
Accessing the Model 3
TRENDS Model Input
2.1 New Capacity 4
2.2 State Gasoline and Diesel Fuel Variables 4
2.3 Federal Gasoline and Diesel Fuel Variables 7
2.4 Indexing the Motor Fuels Tax 8
2.5 Vehicle Registration Fee Variables 9
2.6 Percent of Revenue Dedicated to Transportation 9
2.7 VMT Tax Variables 10
2.8 Fuel Efficiency Variables 10
2.9 Fund 006 Allocations 13
2.10 Maintenance Variables 14
2.11 Expense Variables 15
2.12 Bond Finance Variables 19
2.13 Population Option 22
2.14 Local Options 23
2.15 Output Option 26
TRENDS Model Output
3.1 Summary of Variables Chosen for Analysis 28
3.2 Summary of Revenues and Expenses by Year 28
3.3 Revenues minus Expenses by Year Graph 29
3.4 Cumulative Revenues minus Expenses by Year Graph 30
3.5 Revenue/Expense Statement 2009-2030 30
3.6 Revenue/Expense Statement 2009-2035 31
3.7 Revenue Statement for Local Options Selected 2010-2030 32
3.8 Revenue Statement for Local Options Selected 2010-2035 32
Appendices
Appendix A How Population Projections were Estimated
Appendix B Definition of Commercial and Personal Vehicles
1. ACCESSING THE MODEL
The TRENDS is available on the web at http://trends-tti.tamu.edu. Click on the “Proceed” button to begin the analysis.
The TRENDS model will take you through all of the parameters that must be considered in order to produce a result. Once you click on the “Proceed” button on the first page of the model, the following screen will appear:
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