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82 2.5.3Freeway Performance Measurement: team that airport APMs, although intrinsically very safe, NCHRP Project 3-68 may result in passenger injury when the system is not used correctly. Such isolated instances occur when trains perform The final area of highway performance measurement is an emergency braking while passengers are not either seated discussed in this section and concerns the final report and or holding onto a stanchion, handrail, or strap, and when guidebook of NCHRP Project 3-68, "Guide to Effective platform or vehicle doors close on passengers that attempt Freeway Performance Measurement," produced as NCHRP to enter or exit a train after the warning chime has sounded Web-Only Document 97: Guide to Effective Freeway Perfor- and the doors have begun to move. These instances are the mance Measurement [2.5.6]. reasons most often cited when litigation is involved. Some The report recommends a total of 47 measures in 12 cate safety measures that may be interesting to track in these gories as core freeway performance measures, and an addi- contexts are the number of emergency brakings per thousand tional 78 measures in nine categories as supplemental freeway interstation runs performed and the number of door closing performance measures. alarms per thousand dwell sequences. These safety-related The research team focused on the core performance mea- measures may be useful in gauging the risk of exposure to sures and found several that were the same as or similar to passenger injuries for these isolated instances. Theoretically, measures previously discussed in this section of the appendix. the higher the value of the measure, the greater the risk of As such, those are not reconsidered here. However, there are exposure. The lower the value of the measure, the lower the three measures that were found to merit exploration in terms risk of exposure. of their applicability to airport APMs: vehicle miles of travel (VMT), safety, and energy consumption. Consumption per Vehicle Mile Traveled Vehicle Miles of Travel The report recommends a performance measure of fuel Vehicle miles of travel is the product of the number of consumption per VMT, which is calculated based on the vehicles traveling over a length of freeway times the length of modeled gallons of fuel consumed on a freeway divided by the freeway. This measure is also used in the APM industry, the freeway VMT. A variation of this measure may be use- except that it is based on the distance the vehicles travel over ful in the APM industry. Because APM systems use electrical the length of the revenue areas of the system guideway. The energy rather than fuel (gas/diesel) energy, the correspond- numbers of fleet miles and/or average annual vehicle miles ing measure would be electrical energy consumption per are used regularly in the development of fleet sizes, maintenance vehicle mile traveled. Designers today use this measure as and storage facility sizes, preventive maintenance schedules, part of the process of estimating O&M costs for APM sys- and cost estimates for operations and maintenance of APM tems. It remains to be seen, however, if this measure would systems. Although the research of airport APM literature be useful beyond that. This measure may be relevant in the performed for this memorandum did not reveal performance measurement of freeway performance because roadway measures employing a vehicle- or fleet-mile component, it vehicles often can be standing still or creeping in bumper- may nevertheless be useful in comparing airport APM systems. to-bumper congestion. As congestion gets worse, the mea- For example, annual fleet mileage may be useful as a stand- sure would theoretically reflect that (i.e., the gallons of fuel alone measure to describe an APM system as compared to other consumed would increase while VMT decreases). Although APM systems. A measure incorporating vehicle mileage could APM systems consume electrical energy when standing still, also be useful, such as the number of platform door failures the systems are not susceptible to the type of congestion and per vehicle mile traveled. delays seen on freeways, and because of this, it is not expected that this measure as applied to airport APM systems would be meaningful. The core measures listed for safety (quality of service) in the report for NCHRP Project 3-68 specifically apply to 2.6Conclusion crashes (i.e., total crashes, fatal crashes, overall crash rate, fatality crash rate, and secondary crashes). Any measure- It is undeniable that automated people movers are playing ment related to crashes would not be applicable to the APM a vital role in various airports and activity centers around industry since crashes almost never occur. However, there the world. APM systems transport people from their origin are some safety measures that may merit further exploration to destination with a high degree of reliability, comfort, and for airport APMs. It has been the experience of the research speed. Given their importance, it is essential for APM operators

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83 and decision makers to evaluate and manage their systems in covering efficiency, effectiveness, and customer perspectives. using a set of performance measures. On the other hand, performance measurement methodolo- The base of literature on transportation performance gies are still evolving, and there is no uniformly compiled measures of other modes is large, especially when compared framework for various agencies due to the diversity of systems with that of APM systems. With the long history of devel- and their respective service areas. Nevertheless, the material oping, improving, and applying performance indicators in reviewed in preparation of this appendix served as a road map the transportation planning and operations fields, transit for the project team to develop the guidebook for perfor- performance measures, for example, are fairly comprehensive mance measures of airport APM systems.