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16 Objectives and corresponding performance measures are type of maintenance being performed, customers can often reflected in the various plans or programs of transpor- be viewed as road users, those who pay for the roads, tation agencies. A number of organizations have developed and owners of property adjacent to roads that experi- performance-based plans that include maintenance mea- ence spillover effects such as the spread of invasive sures (Cambridge Systematics, Inc. 2000). plants from the right-of-way. Examples of customer- oriented outcomes are as follows: Performance-based planning has become common today in a large number of DOTs. In general, performance-based Smoothness of pavements planning focuses on the projected outcomes of poten- Visibility of signs and markings at night tial investments and the extent these investments support Cleanliness of rest areas department policies. Performance-based planning uses Amount of litter along the road systematic procedures and good analysis, and it relies on Traffic signals quickly restored to operating con- objective asset data and management systems. Goals and dition after they stopped working properly (i.e., objectives, corresponding performance measures, trade-off response times are frequently a part of performance- analysis, and target setting are among the main character- based maintenance contracts). istics of performance-based planning. The way of defin- ing, combining, and aggregating performance measures is Another class of outcomes is expressed in economic critical to success (Neumann and Markow 2004). The use terms; for example, reduction in accident costs, travel time of performance measurement and targets helps top manage- costs, and vehicle operating costs. These economic impacts ment steer an agency in the desired direction and deal with are important outcomes, but they are difficult to measure the trade-offs in addressing competing and complementary and incorporate into a performance-based contract. For goals and objectives. For purposes of performance-based example, to calculate accident costs, one needs to know planning, DOTs can draw on many recent compilations of the number of fatalities and personal injuries, as well as performance measures, including those relevant to mainte- "property-damage-only" accidents that occur on a stretch of nance management (Booz Allen Hamilton 2002; Cambridge road over a certain period of time. The economic costs are Systematics, Inc. 2000, 2006; Hyman 2004). obtained by multiplying these respectively by the imputed economic cost of a death, an average injury, and an average property-damage-only accident. An exception to difficult BASIC CATEGORIES OF MEASURES user cost calculations are lane rental charges to discourage contractors from erecting work zones and closing lanes dur- PBMC requires a clear understanding of the fundamental ing peak periods or unnecessarily disrupting traffic. types of measures (Hatry, Fountain, Sullivan, and Kremer 1990; Government Performance and Results Act 2003; Hyman 4. Explanatory Variables. It is desirable for the con- 2004). The basic categories of measures are as follows: tracting agency and contractor to keep track of variables that can help explain resource utilization, 1. Inputs. These are resources applied to maintenance. outputs, and outcomes. Many explanatory variables They usually consist of labor, equipment, materials, are outside the control of the contractor and agency and the associated financial expenditures. In some and include traffic growth, weather, emergencies, and instances, resources can include other things; for terrain. Accounting for explanatory variables outside example, facilities or land. the contractor's control provides a basis for adjusting incentives and disincentives and more fairly allocat- 2. Outputs. These are accomplishments or, in other ing risk. words, how much work gets done. Traditional mainte- nance management systems record accomplishments Performance-based contracts may include more than one (outputs) and resources used (inputs) upon comple- type of measure. For example, there may be a combination tion of work. Some performance-based contracts of outcome and output measures along with method specifi- specify the outputs to be achieved. Examples of out- cations (possibly including equipment requirements). How- puts include lane-miles of bituminous resurfacing or ever, the trend is toward reduction or elimination of method linear feet of guardrail replaced. The amount of work specifications and an increasing orientation toward custom- done is a reflection of the efficiency and effectiveness er-oriented outcomes as opposed to outputs. of the organization performing the maintenance. In sum, while PBMC may involve many things, it is 3. Outcomes. These are the results or changes that evolving toward a contracting procedure that provides both occur as a result of maintenance. To an increasing disincentives and incentives for achieving measurable tar- degree, PBMC is concerned with outcomes that are gets or standards based on outcome-oriented performance important to customers of roads. Depending on the specifications.