"TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 378: State Highway Cost Allocation Studies examines the history and evolution of highway cost allocation study practice and explores the current state of the practice"--Publisher's description.

This study was commissioned by INDOT to investigate the cost responsibility and revenue contribution of highway users with regard to the upkeep of Indiana's state and local highway infrastructure. For revenues, user and non-user sources were considered. The highway users were represented by the 13 FHWA vehicle classes, and the study was based on 2009-2012 data on expenditures and revenues. The study framework duly recognized the dichotomy between attributable and common costs. For allocating the attributable costs to the vehicle classes, ESALs, AASHTO loading equivalents, and PCEs were used; for allocating common costs, VMT was used. For each vehicle class, the share of revenue contribution was compared to the share of cost responsibility to determine respective equity ratios and thus to ascertain the extent to which vehicles in each class may be currently underpaying or overpaying their cost responsibilities. The study also determined the distribution of fuel purchases and travel by out-of-state vehicles on Indiana's highways; this analysis was required to further refine the results of the cost allocation and to quantify the magnitude of any imbalance between the out-of-state travel and share of consumption on Indiana's infrastructure and the revenue from such out-of-state vehicles.Pavement and bridge expenditures were found to have a dominant share of the overall expenditures on Indiana's highway system. It was determined that the user revenue sources contributed approximately 63.5% of the total state funding for highway expenditures and 36.5% were from non-user revenue sources. The inability of user revenue sources to cover the total highway expenditure and the consequent partial reliance on non-user sources constitute a rather unstable funding situation particularly because the non-user sources are characterized by significant variability.This study found that inequities exist, albeit in varying degrees, among the highway user groups. Of the 13 vehicle classes, classes 1-4 were found to be overpaying their cost responsibilities while classes 5-13 are underpaying. The results of the equity analysis are generally consistent with those of studies carried out at other states.