National accident sampling system sample design, phases 2 and 3 : executive summary

6256810Final reportPDFTech ReportDOT-HS-805-273DOT-HS-7-01706Accident analysisAccident investigationUnited States. National Highway Traffic Safety AdministrationEdmonds, H. JohnHanson, Robert H.Morganstein, David R.Waksberg, JosephJohn A. Volpe National Transportation Systems Center (U.S.)Westat, Inc.NTL-SAFETY AND SECURITY-SAFETY AND SECURITYNTL-SAFETY AND SECURITY-Human FactorsVolpe National Transportation Systems Center, Technical Reference CenterBTS Data DirectoryThis report describes the Phase 2 and 3 sample design for theNational Accident Sampling System (NASS). It recommends a procedurefor the first-stage selection of Primary Sampling Units (PSU's) andthe second-stage design for the selection of accidents for investigation.Cost models are developed to estimate the operating characteristicsof the NASS. The design features extensive use of stratificationand clustering. Controlled probability selection is used toinsure geographic dispersion of the 75 recommended investigationsites, including the initial 10 NASS pilot sites