Understanding of and Preference for Dynamic and/or Static Rating for Rollover

Understanding of and Preference for Dynamic and/or Static Rating for Rollover

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  Virtually all participants were able to identify the difference between the tests for the Static Stability Factor (SSF) Rollover Rating and the Dynamic Test rollover rating, i.e., that the first is a vehicle measurement and that the latter involves maneuver tests.
  
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  Most participants preferred a combined rating, especially once they understood that 95% of real-world rollovers are accounted for by SSF. Those who said they should be presented separately thought they would provide consumers with more information; but they also thought that the different (5 pt vs.3 pt) rating scales presented would confuse people. Many thought that a dynamic test was more realistic.
  
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  Some participants had trouble understanding “track width” and “center of gravity height” in the description of SSF.
  

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  Even though most participants did not explain rollover in the same way it was described to them, most stated that the description of rollover they read (from NHTSA web-site information on rollover) was understandable.
  

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  Some of the rollover terminology; “rollover resistance rating,” “tripped by” and especially “tripped by a ditch,” were confusing or did not make sense to many of the participants.
  

Preferences for Presentation of Rollover Ratings and Information

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  Participants were presented with stars, numbers, letters and descriptive language as alternatives for presenting rollover ratings. Stars were overwhelmingly preferred by both interview and focus group participants. They clearly disliked number ratings, and were ambivalent about letters and descriptors. Graphics presented to participants are shown in Figure 2 and in the report “Findings of 21 In-Depth Interviews and 12 Focus Group Discussions Regarding Vehicle Rollover,” which is available in the docket for this notice.
  
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  Participants accurately interpreted the star ratings, with and without the key that explained what each star meant and which was better. However, many did not fully grasp that the ratings were vehicle ratings and were therefore confused by or did not find credible the actual data sets that showed percentages from over 40% to under 10% for rollover risk.
  
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  When presented with a bar graph that showed an individual vehicle among all vehicles, most interview participants found the bar graph complicated and too vague. Some said it might be useful to decide between different vehicle classes. The bar graph was refined visually and presented as a way of checking an individual vehicle through the web-site for the focus groups. When shown this graph depicting where a certain vehicle ranked in relationship to other vehicles in it’s class, and against all classes as well as where it fell in the star rating range, most participants understood it and thought it useful.
  

Preferences for Rating Levels for Rollover Ratings

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  Nearly all of the participants preferred five rating levels. Alternatives of three and ten ratings were presented through the use of numbers, letters, half-stars and narrative descriptors. Most said they did not like the half stars, but when probed said it might make a difference in whether or not they would consider a vehicle. Interestingly, many assigned different values to half-star ratings; e.g. 3 ½ stars was considered more
  

Figure 2a. Graphics presented to focus groups – 4 out of 5 stars, without key