Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 32


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 31
31 respondents themselves and their organizations. Opinion statistics automatically in survey reports. For paper surveys, questions were subjective and called for subjective, judg- the survey statistics were obtained from Excel spreadsheets mental responses, mostly in the form of Likert scale ratings. used to enter and reduce the data. These responses should not be misinterpreted as objective facts. Questions about specific carrier practices asked for yesno answers and, when the answer was "yes," asked for MOTOR CARRIER SAFETY-MANAGER an effectiveness rating on a Likert scale. These were on SURVEY METHODS the safety-manager survey forms only. Questions about the This section describes methods specific to the safety-manager respondents themselves (e.g., years of experience) were also surveys. Safety managers were the respondent group of great- objective. All of the caveats discussed earlier regarding sam- est interest for the study. These individuals have company titles ple representativeness apply to all questions on both forms. such as safety manager, safety director, director of compli- Thus, none of the survey results on either form can be gen- eralized to larger respondent groups or populations such as ance, and vice president for safety (and/or compliance). A few "North American carrier safety managers" or "experts in have titles relating to operations. The respondent pool (sam- motor carrier safety." The value of the survey results is not ple space) consisted of individuals participating in national based on representativeness to larger populations, but rather industry groups supporting safety, or who had attended on the respondents' answers to specific questions relative safety meetings and whose contact information was available to other, similar questions. For example, which operational to the project team. As discussed in the previous section, the factors are most associated (positively or negatively) with respondent pool may be characterized as representing safety- risk? Which specific operational practices were rated as most conscious carrier safety or operational managers who are will- safety-effective? ing to participate in such research. All of the sampling and data analysis issues discussed previously apply to the safety- manager survey. Non-Use of Response Percentages Per CTBSSP policy, the survey results tables in this chap- Questionnaire Design and Content ter, and survey results cited elsewhere in this report, do not include results percentages. Instead, raw numbers are cited The safety-manager survey questionnaire consisted of the fol- (e.g., "42 of 51 respondents . . ."). This practice reduces lowing general sections: the likelihood that survey results will be misinterpreted or incorrectly cited as representing larger respondent pop- A brief statement of the study and survey purpose, with ulations. Readers may generate their own percentages, but a confidentiality assurance. they should not be reported as being representative of larger Two related five-choice questions on general factors groups. affecting safety and crash risk (used in the paper form only). These questions were omitted from the survey form to help increase the response rate. Likert Scale Means Fifteen driving situations or operational practices, each rated on a -3-to-+3 Likert scale (-3, -2, -1, 0, +1, +2, +3) Likert scales are numeric rating scales, often with five choices for effect on fleet safety. Negative values were for numbered from 1 to 5. Likert scales usually have word descrip- "reduces fleet safety," whereas positive values were for tors for each choice, or "anchor" choices at the ends and per- "improves fleet safety." One item (item 9) was omitted haps the middle. Two different Likert scales were used in the from the bus version because it was not applicable to project surveys: bus operations. Eleven carrier operational practices and tools, with a two- A seven-point scale relating driving situations and oper- part answer for each: ational practices to crash risk. Choices ranged from Yesno for whether the practice was used by the man- "reduces fleet safety (-3)" to "improves fleet safety (+3)." ager's fleet; and A five-point scale rating the safety effectiveness of car- If yes, a 15 Likert scale to rate the practice's safety rier operational practices. Choices ranged from "highly effectiveness. ineffective (1)" to "highly effective (5)." Some pairs of One item (item 21) was omitted from the bus version questions were intentionally constructed to present oppo- because it was not applicable to bus operations. site strategies. A single four-choice question on the general relation between carrier efficiency and safety. Results are provided here in the form of respondent counts An open-response question asking what operational for each choice, along with the weighted arithmetic mean of efficiency or practice contributed most to fleet safety. all choices. Median responses are also provided for the seven- An open-response question asking for any other point scale items. TRB's online survey service provided these comments.