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47 CHAPTER 6 DATA LIMITATIONS The following data limitations were identified during the preparation of this synthesis: ⢠MCMIS provides only limited data on intrastate firms. This reporting method means, for example, that school bus contractors that operate intrastate only, of which there may be a significant number, are not fully reported by MCMIS. While industry associations provide esti- mates of this missing information through surveys, their data may not be comprehensive. ⢠NHTSA reports injuries and crashes in the National Automotive Sampling Systemâs General Estimates Sys- tem (NASS GES) for the aggregate category of âbuses.â As a result, statistics on bus-related incidents include motorcoaches, school buses, and transit buses. Because NHTSA does report school bus-related incidents sepa- rately, a combined estimate of transit bus and motor- coach injuries and crashes can be obtained by subtract- ing the school bus data. ⢠For school bus statistics, NHTSA does not distinguish between publicly owned school buses and privately owned school buses. There is also no distinction between school bus body types being used to transport pupils and non-school buses used as school buses in the pub- lished statistics. Further analysis of the source NASS- GES data files could provide additional refinement of these data. ⢠Economic and financial data often are limited. For the trucking industry, a key source is the Motor Carrier Annual Report, which is derived from U.S. DOT filings from for-hire carriers with more than $3 million in annual revenue. Although this information is very detailed, it may not accurately represent the financial and operating profiles of small trucking operators and private opera- tors. Data on operating ratios, while available for the trucking and motorcoach industry through the Bureau of Transportation Statistics, are not reported for school bus operators (only approximately one-third of which are for-hire contractors). Operating costs per mile also are not readily available for the school bus industry. ⢠The definition of a school bus varies from state to state and is sometimes based on function and sometimes based on body type. ⢠Historical vehicle-miles traveled data for motorcoaches and school buses are not readily available. ⢠Little data exist on motorcoach and school bus driver schedules and hours worked. Specifically, industry asso- ciations do not collect timesheet or payroll data that would make it possible to identify the most common driver shifts and the percentage of drivers that work these shifts.