Plantation forestry and dairy farming land-use impacts on potential wear of rural roads

Abstract

Productive land-use requires vehicular traffic that may cause wear and damage to rural roads. This is of particular interest to territorial authorities responsible for planning and funding the maintenance of these roads. Debate sometimes ensues over the need for differential rates or road user charges for different land-uses. Rural land-use change is occurring around the world; in some areas moving from agriculture to forestry and vice versa in other areas. Two case study properties in New Zealand were selected to evaluate the effects of dairy farming and plantation forestry land-uses on vehicular traffic and potential road damage. Semi-structured interviews were used to derive expected traffic counts by vehicle type and management activity. Pavement design formulas were used to calculate equivalent standard axle load (ESAL) values and vehicle damage factors (VDF). Dairy farming generated over seven times the amount of traffic compared with plantation forestry, 21.5 versus 2.9 vehicles per hectare per year. Almost three-quarters of the dairy farm traffic and half of the plantation forestry traffic fits into the “light” vehicle class which contributes little to road wear. The calculated VDF for dairy farming was half that of plantation forestry; 0.43 versus 0.85 ESAL per vehicle. The total ESAL value for dairy farming, however, was four times higher than that for plantation forestry. Changing land-use from plantation forestry to dairy farming, or vice versa, could have a significant effect on the rate of wear and damage on rural roads.