After the construction of a pavement system, deterioration occurs because of traffic loading and weathering action and results in the formation of various types of distresses and an increase in pavement roughness. “Roughness” can be defined as irregularities of pavement surface that affect driver safety and increase user costs, including fuel consumption, repair and maintenance, depreciation, and tire costs. In this study, pavement roughness was predicted with the use of the newly released Mechanistic–Empirical Pavement Design Guide for levels of initial roughness condition. Four alternative maintenance and rehabilitation (M&R) strategies were used to estimate the life-cycle cost of pavement over a 35-year analysis period. Various categories of user costs were calculated on the basis of different cost models and from data reported in the literature. From this analysis, pavement roughness was found to affect user costs dramatically. A comparison was made between agency investment and user costs related to pavement roughness. The results of this analysis showed that agency costs were small compared with roughness-related user costs over the life of the pavement (less than 4% of total costs) and that agency investment in increased rehabilitation activities could have a 50-fold return in the form of reduced user costs. A strong case is made for the critical importance of investing in enhanced M&R activities to reduce pavement roughness. This case is strengthened by hypothesized benefits in pavement system sustainability through reduced user fuel costs and reduced tire wear and increased remaining life of pavement.