Conference Proceedings 26 - Transportation Research Board

MEASURING THAT WHICH CANNOT BE MEASURED 121• Quality:–Average speed weighted by person miles traveled,–Average delay per vehicle,–Average door-to-door travel time,–Reliability (variance of average travel time orspeed),–Maneuverability (vehicles per hour per lane inpeak hours), and–Auto or transit travel time ratio;• Accessibility:–Connectivity to intermodal facilities (percentagewithin 5 mi),–Dwelling unit proximity,–Employment proximity,–Industrial warehouse facility proximity,–Percentage of miles of bicycle accommodationin right-of-way,–Percentage of miles of sidewalk coverage,–Transit coverage (percentage of person minutesserved),–Transit frequency (buses per hour), and–Span of service (hours per day); and• Utilization:–Percentage of system heavily congested (LOS Eor F),–Vehicles per lane mile,–Percentage of travel heavily congested,–Duration of congestion (vehicles per hour permile at LOS E or F), and–Transit load factor (percentage of seats occupied).Of interest in this set of measures is the effort tomeasure reliability of travel. Reliability was definedas the percentage of travel on a corridor that takesno longer than the expected travel time, plus somemeasure of acceptable additional time. Loop sensorsused as part of the state’s intelligent transportationsystem (ITS) program were used to collect the datanecessary for this performance measure.OUTCOME MEASURES AND TRANSPORTATIONSYSTEM PERFORMANCE: CONCLUSIONSThis paper began by posing several questions concerningthe use of societal outcome measures in thecontext of performance-based planning and decisionmaking. Its conclusions could be unsatisfying becausethe answer to these questions often depends on thedecision-making context and the specific issues facinga community. However, I believe that performancebasedplanning should exhibit several key characteristics(based on Meyer, 1995).System Performance Linked to FundamentalRoles of TransportationThe measure of whether the transportation system isperforming as expected should relate to a broad perspectiveon what role transportation plays in a metropolitanarea. Congestion on individual links in thenetwork does not inform much about how the systemperformance is affecting quality of life, economic development,or environmental quality. Performancebasedplanning should thus consider a broader rangeof issues than just operational efficiency of the modalnetworks.Outcomes and OutputsInitial experience with performance-based planningsuggests that agencies measure success by the level ofoutput produced. For example, the number of lanesper mile maintained or constructed or number of revenuebus-hours provided shows how productive anagency can be. These are indeed important indicatorsof the amount of service provided in a region. However,in keeping with the characteristic described previously,outcome measures are also important indicatorsof system performance. Outcome measuresrelate to the ultimate effect of the transportation systemon a community, such as quality of life, environmentalhealth, equitable distribution of benefits andcosts, economic development, safety, and security.Outcome measures should be part of the performance-basedplanning process.Mobility and AccessibilityProviding individual mobility and accessibility to urbanactivities is an important goal for transportationplanning, and I would argue that it is a critical precursorto the types of societal outcomes desired.Many MPOs have defined measures that indicate thedegree to which the transportation system is providingacceptable levels of performance. However, measuresof mobility and accessibility prompt the question:mobility and accessibility for whom? Thedistributional effects of transportation investment ondifferent socioeconomic groups and on different geographicareas of a metropolitan region strongly suggestthat performance-based planning should bebased on a market segmentation approach that identifiesexisting and future travel markets as well as