Conference Proceedings 26 - Transportation Research Board

82 PERFORMANCE MEASURES TO IMPROVE TRANSPORTATION SYSTEMS AND AGENCY OPERATIONSTo understand the issues, data and measures wouldbe required at several levels. Some of the questionsfor which data and goals would be required includethe following:• Are pavements performing in the manner expectedby the pavement management systems?• If pavements are not performing as expected, isthe problem with all pavements or with a particularpavement type?• If asphalt pavements are not performing to standard,is the problem in a particular type of mix?• If it is a specific mix, is the problem in materials,construction, base, or other factors?These questions suggest a hierarchy of measures (Table3), all of which are needed to understand the program.Obviously, not all of these measures need to be orshould be reported generally. Policy makers in a legislatureor governor’s office will probably be interestedin only the highest level measurement. In addition,the highest level of agency management willprobably have limited interests. Lower-level managersand technical staff will want and need to knowthe details that underlie the global measure.Even this short hierarchy suggests a complex system.Although it is complex, it is not new to mosthighway agencies. Most agencies have some type ofpavement management system. Such systems containmany assumptions about performance at differentlevels of detail that are effectively performance measures.Similarly, many design standards contain performanceassumptions that can be used as performancemeasures. If they are understood to bemeasures and are used to better understand an issue,they can help to improve agency performance. Moreover,they can be used without creating complex newsystems and, probably, without collecting significantnew data.Defining and Standardizing DataFor data to be used with confidence, they must beconsistently defined. Standardization strives to definedata to a degree that minimizes subjectivity and maximizesobjectivity with respect to establishing a dataitem to promote accuracy and repeatability. Standardizeddata also are necessary for successful dataintegration. For example, how much has an agencyspent on a given program? This is a frequently askedquestion, a question for which there can be manyanswers that are different but all correct. An accountantprobably would answer in terms of dollars thathave left the agency, on an expenditure basis. A federalprogram manager would probably answer interms of the dollars moved to federal agreement, onan obligation basis. A program manager might answerwith the amount contracted, on an encumbrancebasis. Within their limits, all of the answersare correct, but they are different. If such informationis reported as a part of a performance managementsystem, the agency must determine which answer ismost relevant to the audience and standardize thisbasis for answering. Another simple example, determiningthe length of a highway ramp, illustrates thepoint in the physical inventory world (Figure 3).Where does the ramp start and end? There is no rightanswer, but the answer must be consistent.To standardize data, the data element in questionmust be understood. Data modeling efforts that includeusers or potential users of common data mayprove useful for establishing and defining data to adetail that facilitates standardization.Quality control is also necessary to standardizeand use data with assurance. The Wisconsin Departmentof Transportation (WisDOT) recently implementeda quality control data-collection audit of itsstate highway inventory data. The audit focuses onsampling a percentage of the annual data updates.The results of the first year’s audit have already generatedbenefits. The audit highlighted some key areaswhere inconsistencies were present in the collectedTABLE 3Hierarchy of Pavement Performance MeasuresMeasure Use AudienceNumber of bad miles Overall pavement performance Policy makersPerformance of pavement type Measure overall performance System managersPerformance of specific pavementMeasure performance withinSystem managersdesignspavement typePerformance of specific pavementdesign componentsMeasure performance of pavementcomponentsSystem managers, engineers,contractors