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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- ˇ 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 ˇ 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 ˇ 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.
ˇ Eleven carrier operational practices and tools, with a two-
ˇ 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
ˇ 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. ˇ A single four-choice question on the general relation
between carrier efficiency and safety.
Results are provided here in the form of respondent counts ˇ 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- ˇ An open-response question asking for any other
point scale items. TRB's online survey service provided these comments.
