Pavement damage and road pricing
The number and weight of the vehicles that use a road significantly influences the pavement damage and cost of the construction and maintenance. The studies conducted by Federal government and various state governments conclude that heavy vehicles typically do not pay their share of road damage costs, while lighter vehicles tend to be taxed for more than their share. The objective of this thesis is to quantify the pavement damage caused by different classes of vehicles, and to find an efficient pricing mechanism to regulate demand for highway services.
Several models were reviewed and KENLAYER was selected for the purposes of this analysis. The analyses show that a 4-axle truck causes more pavement damage, as compared to a 5-axle truck, when carrying the same amount of the load. When fitting a curve to the data set, the compressive strain curve follows the AASHTO 4th power curve more closely, while the tensile strain follows a 3rd-power curve. The model demonstrates that the same truck can cause different damage depending on load, whether empty, partially loaded or fully loaded; and how that load is distributed over the axles. A damage simulation exhibited that an equal load distribution over the axles yields the least pavement damage. Lower speeds and congestion significantly reduces the design life of the flexible pavements. Higher tire pressure results in more damage due to the increase in load per-unit area.
The current tax structures do a poor job of capturing the pavement damage. Implementation of a real-time weight-mile tax based on actual weight, speed and tire pressure promotes two distinct objectives: one is to apportion the cost of road construction and repair in an equitable manner among users, according to their fair share of damage; second is to discourage the use of heavy axle-loads and thus, reduce the wear on the road system. Establishing a pavement damage tax based on speed would ultimately reduce congestion in typical peak hours, as well as pavement damage. It could be concluded that the weight-mile tax is a road management device as well as a revenue source.