Statistical Evaluation of Different Sample Sizes for Local Calibration Process in the Highway Safety Manual
An approach to determine a statistically reliable sample size for developing local calibration factors (LCFs) was proposed to complement the Highway Safety Manual’s (HSM) sampling guidance. The HSM suggests a minimum sample size of 30 to 50 sites per facility type with at least 100 annual crashes. However, the HSM fails to provide clear guidance on how to determine a minimum sample size to ensure the statistical reliability of LCFs. The proposed approach based on the finite population correction (FPC) factor determined minimum sample sizes by considering trade-offs between the desired error levels of the estimated LCFs, confidence levels, and sample standard deviations. The sample sizes by facility types were drawn on the basis of various statistical assumptions; then they were assured by the comparisons between FPC-based samples and the HSM-based samples. LCF values estimated from the HSM-based sample sizes yielded inconsistent reliabilities depending on the facility types. In contrast, those estimated from the samples by the FPC-based approach satisfied the desired reliabilities of the LCFs for all facility types.
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Availability:
- Find a library where document is available. Order URL: http://worldcat.org/isbn/9780309369305
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Authors:
- Shin, Hyeon-Shic
- Yu, Jeong Whon
- Dadvar, Seyedehsan
- Lee, Young-Jae
- Publication Date: 2015
Language
- English
Media Info
- Media Type: Print
- Features: Figures; References; Tables;
- Pagination: pp 94–103
- Monograph Title: Statistical Methods and Highway Safety Performance
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Serial:
- Transportation Research Record: Journal of the Transportation Research Board
- Issue Number: 2515
- Publisher: Transportation Research Board
- ISSN: 0361-1981
Subject/Index Terms
- TRT Terms: Calibration; Reliability (Statistics); Statistical analysis; Statistical sampling; Traffic crashes
- Identifier Terms: Highway Safety Manual
- Subject Areas: Highways; Planning and Forecasting; Safety and Human Factors; I80: Accident Studies;
Filing Info
- Accession Number: 01557454
- Record Type: Publication
- ISBN: 9780309369305
- Report/Paper Numbers: 15-4639
- Files: PRP, TRIS, TRB, ATRI
- Created Date: Mar 20 2015 3:21PM