Investigation of Rainfall and Regional Factors for Maintenance Cost Allocation (5-4519-01-1)

The existing formulas used by the Texas Department of Transportation (TxDOT) to allocate the statewide maintenance budget rely heavily on inventory and pavement evaluation data. These formulas include regional factors and rainfall indices that vary by district to account for differences in environmental and soil factors across the state. The existing regional factors were developed in the 1990s and were intended to reflect differences in environmental and soil factors between districts. It is not known how these factors were calculated since no documentation is available that explains their development. Since the regional factors were introduced, the Texas Transportation Institute has completed a project in which a database of climatic and soil factors were compiled to characterize the variation of climatic and soil conditions across Texas. TxDOT's Maintenance Division realized the potential value of using this information and directed an implementation project to re-examine the existing regional and rainfall factors with the objective of revising the current factors to better reflect differences in climatic and soil conditions between districts. This report documents the evaluation of the existing rainfall and regional factors and the development of a revised set of factors for maintenance cost allocation.