DOT HS 811 234
`
`(cid:39)(cid:72)(cid:70)ember 2009
`
`Drivers’ Mistakes When Installing
`Child Seats
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`Page 1 of 92
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`Nuna Exhibit 1008
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`This publication is distributed by the U.S. Department of
`Transportation, National Highway Traffic Safety Administration,
`in the interest of information exchange. The opinions, findings
`and conclusions expressed in this publication are those of
`the author(s) and not necessarily those of the Department
`of Transportation or the National Highway Traffic Safety
`Administration. The United States Government assumes no
`liability for its content or use thereof. If trade or manufacturers’
`names or products are mentioned, it is because they are considered
`essential to the object of the publication and should not be
`construed as an endorsement. The United States Government
`does not endorse products or manufacturers.
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` Technical Report Documentation Page
`
`2. Government Accession No.
`1. Report No.
`
`DOT HS 811 234
`
`4. Title and Subtitle
`Drivers’ Mistakes When Installing Child Seats
`
`
`7. Author(s)
`Yi-Fang D. Tsai and Michael Perel
`
`9. Performing Organization Name and Address
`NHTSA
`1200 New Jersey Avenue SE
`
`Washington, DC 20590
`12. Sponsoring Agency Name and Address
`National Highway Traffic Safety Administration
`NHTSA, NVS-331
`1200 New Jersey Avenue SE
`
`Washington, DC 20590
`
`3. Recipient's Catalog No.
`
`
`5. Report Date
`December 2009
`
`
`
` 6. Performing Organization Code
`
`8. Performing Organization Report No.
`
`10. Work Unit No. (TRAIS)
`
`11. Contract or Grant No.
`
`13. Type of Report and Period Covered
`
`NHTSA Report
`
`14. Sponsoring Agency Code
`
`
`15. Supplementary Notes
`
`16. Abstract
`This study examined the mistakes that drivers made during the different steps taken to install Child Restraint Systems (CRS). The focus of
`this study was to identify the reasons drivers made installation mistakes. The participants were observed during their CRS installation
`
` process where unfolding installation errors lead to clues about why participants had difficulty with their installation. Five experiments
`were conducted to identify common errors installing CRS using seat belts or the attachment system known as Lower Anchors and Tethers
`
`
` for Children (LATCH). The investigation examined the factors that contribute to these errors and identified possible improvements that
`could reduce them. In experiments 1 and 2, 61 participants completed an infant CRS installation to the best of their ability using the
`original CRS instruction manual and their vehicle owner’s manual. Participants were asked to use a “talkaloud” method, where they
`explained whatever they were examining, thinking, doing, and feeling as they went about their task. The CRS installation was video-taped
`
`
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`with their consent. Participants rated their confidence levels, ease of installation, and CRS usability after the installations were completed.
`
`
`
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`All participants who installed the child seat using the seat belt made at least one error. There was a 95% error rate for participants who
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`completed the infant CRS installation using LATCH. Participants expressed confusion with a feature on the CRS or vehicle
`approximately two times for each seat belt and LATCH installation. In experiment 3, 22 participants completed a rear-facing and forward-
`
`facing installation with a convertible CRS. Common installation problems were loose installation (85%), incorrect seat angling (81.8%),
`
`
`and twisted lower anchor straps (50%). Studies 4 and 5 explored CRS installations by parents and caregivers at child seat inspection
`
`
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`events and from parents and caregivers found from local community postings. The installation errors reflected similar common errors
`found in studies 1-3 but to a lesser degree. Loose installation error rate ranged from 46.7 percent to 65 percent (seat belt or LATCH) and
`incorrect angling ranged from 27 to 50 percent in studies 4 and 5, respectively. As participants installed the child seats, they
`
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`acknowledged the difficulty in installing the CRS into the vehicle and with interpreting the manuals but were overly confident that they
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`correctly installed the CRS. Analyses were conducted on the installation errors made by installation type, feature differences across the
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`child seats used, and user ratings.
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`18. Distribution Statement
`Document is available to the public through the
`National Technical Information Service
`www.ntis.gov
`
`17. Key Words
` Child safety seats, Child restraint systems,
`Child passenger safety,
`LATCH,
`Use and Misuse
`
` 19. Security Classif. (of this report)
`
` Unclassified
`Form DOT F 1700.7 (8-72)
`
`
`
`
` 20. Security Classif. (of this page)
`
` Unclassified
`
`21. No. of Pages
`92
`
`22. Price
`
`
`Reproduction of completed page authorized
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`i
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`Page 3 of 92
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`Acknowledgements
`
`
`The authors wish to thank many people and organizations for their time and
`effort. Thanks to our NHTSA colleagues Jessica Butterfield, Jenny Dang,
`Carole Guzzeta, the CPS Technical Group, and Taryn Rockwell, Christina
`Stelmack of Alpha Technology Associate, Inc. for their valuable insights
`and feedback throughout the project.
`
`Special thanks to Heather Hurlock, Kimberley Malinowski and the
`Arlington Auxillary Police department, Donna Honse and the Fairfax County
`Sheriff's Office, John Lehman, Jack Fitzgerald and the Fitzgerald Automotive,
`and Emilie Crown and the Montgomery County SAFE KIDS Coalition for their
`dedication to the community and their support.
`
`Final thanks to the certified child passenger safety technicians that
`volunteered their time to conduct child seat checks, the child seat and
`vehicle manufacturers that gave us permission to use their images and text in
`the design survey, and the participants who took part in the study.
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`Executive Summary
`
`Child restraint systems (CRS) are known to be difficult to install (Taft, 1999; Decina &
`Lococo, 2006; 2004). The current designs of child seats, vehicle seats, and attachment
`mechanisms can lead to problems in child seat installation. To reduce these problems,
`some studies (e.g., Rudin-Brown, C. et al., 2004; 2003) point to a need for more emphasis
`on improving installation procedures and designs for child restraints, instruction manuals,
`and warning labels. Child seats have varying designs that can contribute to installation
`error when they are not intuitive. Identifying why and where parents become confused
`during the installation process can provide insights about what improvements might help
`them. For example, improvements might be needed to simplify CRS instructions and
`
`vehicle owner’s manuals as well as with modifications to the design characteristics of
`child and vehicle seating.
`
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`Research Objectives and Methodology
`
`
`The objective of this research was to identify why drivers are making mistakes when
`installing child seats and possible improvements that might help reduce their errors. The
`main focus of this research was to understand what happens during the installation
`process that leads to errors. Potential interactions between the child seat and vehicle
`design were also explored. Five separate but related studies were conducted. The focus
`of studies 1 and 2 was on understanding novice installation errors with infant CRSs;
`study 3 looked at inexperienced participants installing convertible CRSs, and studies 4
`and 5 observed experienced participants.
`
`This study also aimed to capture a wide spectrum of participants. The populations
`sampled included novices with little to no experience installing a child seat as well as
`parents and caregivers who currently own and use child seats, some of whom were
`observed at child seat inspection events and checkups. An observational “talkaloud”
`method was used to record the problems that first time installers encountered during the
`process of installing infant and convertible child seats. Participants expressed their
`thoughts and insights as they installed their child seat and after the installation process
`was completed. This information as well as observations by a certified Child Passenger
`Safety Technician of mistakes participants made during the installation process was
`analyzed to determine the factors that contributed to any errors or difficulties in
`installation.
`
`Results
`
`
`Installation errors occurred when people installed child seats in vehicles using seat belts
`as well as when using Lower Anchors and Tethers for Children (LATCH) systems.
`Common installation errors such as loose installation and twisted lower anchor or seat
`belt straps were found frequently in the studies, regardless of the participant’s experience
`with child seat installation and whether the child seat installed was an infant or
`convertible child seat. Novices were observed while they installed a rear-facing infant
`seat into their vehicle in studies 1 and 2. Three main errors found during the 37 LATCH
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`installations were as follows: (1) loose installation (73%), (2) installation of both seat belt
`and LATCH systems (45.9%), and (3) twisted lower anchor straps (35.1%). Other
`installation errors included inappropriate recline positions (30.8%) and incorrect carrying
`handle positions (28.2%). Most participants said they were confident that they had
`routed the belt system correctly (71%) during installation, secured the LATCH system
`correctly (72%), or believed that their CRS was installed correctly (87%). Nonetheless,
`only 26.9 percent correctly secured the LATCH system. Most participants shook or
`pushed the CRS to test whether the CRS moved more than an inch from side-to-side.
`
`The high error rate of loose combination seat belt and LATCH installations showed that
`participants still had problems with securing the CRS despite the feeling of “added
`security” that warranted many participants to use both attachment systems
`
`Novices were observed while they installed a convertible child seat in study 3. Common
`errors were loose installation using the LATCH system (85%), installing the child seat at
`an incorrect angle (81.8%), and twisting the lower anchor straps (50%). The confusion
`participants had when referencing the CRS manual or label instructions led to several
`convertible child seat errors such as seat belt or LATCH routing problems (45%). In
`some cases, LATCH-twisting errors resulted from incorrectly switching the routing from
`the rear-facing position to the forward-facing position.
`
`Installations by parents and caregivers with experience using child seats were examined
`in studies 4-5 at inspection events. Their installation errors reflected the common errors
`found with novice participants in studies 1-3 but to a lesser degree. In study 4, the loose
`installation error rate was 46.7 percent (seat belt or LATCH). Twenty-seven percent
`installed their child seat at an incorrect angle (3 rear-facing, 1 forward-facing, N=15).
`This error was also seen in study 5 where one half of the observed participants incorrectly
`angled the child seats (N=32). Loose installation of the CRS occurred for 65 percent of
`the people with convertible child seats using LATCH in study 5. Another common error
`that occurred in 77 percent of the installations was twisted LATCH straps.
`
`After each installation or checkup in studies 3-5, participants were surveyed about their
`experience and asked for design feedback. A majority of participants said that they read
`
`the CRS manual (94.1%) while few reported reading the vehicle owner’s manual
`(36.2%). Some parents suggested that manuals could be improved with clearer diagrams
`and easier set-up guides with fewer steps. Most participants were also unsure how to get
`their CRS installation tight. Some participants were not aware that applying their weight
`or additional pressure to the child seat would help achieve a tight installation. Some
`
`participants said that it was too difficult to pull the straps to secure the LATCH or seat
`belt system tightly.
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`Recommendations
`
`Given that participants were often confused with the instruction manuals and labels,
`errors may be reduced by modifying their designs. Manuals can be made more readable
`and simplified to clearly list each of the steps to install the CRS (Wegner & Girasek,
`2003). The manuals should list common installation problems and methods to check for
`correct fit of the CRS. Labels can provide helpful location cues to remind and inform
`
`parents and caregivers of the steps for a successful child seat installation. Participants
`have commented that some of the pictures in the manuals are confusing because they do
`not provide context and that they cannot find the equivalent objects of interest on the
`child seat. One approach to reduce this confusion may be to add zoomed-out pictures to
`the manuals to provide perspective to the installer. Using a similar color coding scheme
`
`to highlight areas of importance or numbering labels to correspond to instructions (Smith,
`2003) are also possible ways to coordinate information between the manual and CRS.
`
`Another approach that may help reduce installation errors is to put some instructions on
`the child seats near features that require installer adjustment, such as level indicators and
`seat belt lock-off systems. The manuals should provide supplementary, supporting
`information. Human factors design principles such as affordance, color coding, and
`
`intuitive organization may be helpful in efficiently organizing the abundance of
`information provided with the child seat. Numerous parents and novice participants have
`commented on the overwhelming choices and options with child seats. Thus, the
`information provided through manuals, labeling, and web content should aim to be
`intuitive to child seat installers through coherent instructions that are verified to be easy-
`to-understand with user testing.
`
`Future research is needed to evaluate the effectiveness of design improvements in
`reducing installation errors. For example, what design improvements will reduce the
`
`most common error of loose installation? Participant installation differences found
`
`across CRS types allude to possible interactions between varying child seat designs and
`vehicle design. Understanding the variations and its effects on installation will allow
`achieving best fit for child seats.
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`Table of Contents
`
`
`1
`1.1
`
`Background..........................................................................................................................1
`
`Study Objectives ..................................................................................................................4
`
`
` 2
`
`Research Methodology ........................................................................................................6
`
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`Participants...........................................................................................................................6
`
`2.1
`2.1.1 Studies 1-2: Understanding Infant CRS Errors....................................................................6
`
`2.1.2 Study 3: Understanding Convertible CRS Errors ................................................................7
`
`2.1.3 Study 4: Understanding CRS Installation Errors of Parents and Caregivers.......................7
`
`2.1.4 Study 5: Understanding CRS Installation Errors at Child Seat Inspections ........................8
`
`2.2
`Vehicle Characteristics ........................................................................................................8
`
`2.2.1 Studies 1-2 ...........................................................................................................................8
`
`2.2.2 Study 3 .................................................................................................................................8
`
`2.2.3 Study 4 .................................................................................................................................8
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`2.2.4 Study 5 .................................................................................................................................9
`
`2.3
`Equipment............................................................................................................................9
`
`2.3.1 Studies 1-2: Infant CRSs Used ............................................................................................9
`
`2.3.2 Study 3: Convertible CRSs Used.......................................................................................10
`
`2.4
`General Procedure..............................................................................................................11
`
`2.4.1 Studies 1-2 .........................................................................................................................11
`
`2.4.2 Study 3 ...............................................................................................................................12
`
`2.5
`Forms and Interview Process.............................................................................................12
`
`
` 3
`
`Results and Discussion ......................................................................................................13
`
`
`Statistical Analysis.............................................................................................................13
`
`3.1
`Studies 1-2: Installation of Infant CRS..............................................................................13
`
`3.2
`3.2.1 Use of LATCH System......................................................................................................13
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`3.2.2
`Infant CRS Installation Times ...........................................................................................14
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`3.2.3
`Infant CRS Installation Error Rates ...................................................................................14
`
`3.2.4 Study 1: Seat Belt Installation of Infant Child Seats .........................................................15
`
`3.2.5 LATCH Installation of Infant Child Seats.........................................................................16
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`3.2.6 LATCH and Seat Belt Installation.....................................................................................17
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`3.2.7
`Infant CRS Feature Differences.........................................................................................17
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`3.2.8 Vehicle Seat Feature Differences.......................................................................................18
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`3.2.9 Reasons for Installation Mistakes ......................................................................................18
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`3.2.10 Study 1: Child Installation .................................................................................................20
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`3.2.11 Infant CRS Usability Ratings.............................................................................................21
`
`3.3
`Study 3: Installation of Convertible CRS ..........................................................................23
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`3.3.1 General Installation............................................................................................................24
`
`3.3.2 Convertible CRS Installation Times ..................................................................................25
`
`3.3.3 Seat Belt Installation..........................................................................................................26
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`3.3.4 LATCH Installation ...........................................................................................................26
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`3.3.5 Convertible CRS Feature Differences ...............................................................................27
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`3.3.6 Convertible CRS Usability Ratings ...................................................................................28
`
`3.4
`Study 4: Installation Errors of Parents and Caregivers......................................................29
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`3.4.1 General Installation............................................................................................................29
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`3.4.2 Seat Belt Installation..........................................................................................................30
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`3.4.3 LATCH Installation ...........................................................................................................30
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`3.4.4 Tether Installation ..............................................................................................................30
`
`3.5
`Study 5: Installation Errors at Child Seat Inspections .......................................................30
`
`3.5.1 General Installation............................................................................................................30
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`3.5.2 LATCH Installation ...........................................................................................................31
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`3.5.3 Tether Installation ..............................................................................................................31
`
`3.6
`Studies 3-5: Participant Suggested Usability Improvements.............................................32
`
`3.6.1 Vehicle Design Preferences ...............................................................................................32
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`3.6.2 Reported Manual Sections Read........................................................................................33
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`3.6.3 Manual Suggestions: Vehicle Owner's Manual .................................................................34
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`3.6.4 Manual Suggestions: Loose Installation ............................................................................34
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`3.6.5 Combination Seat Belt and LATCH Installation...............................................................35
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`3.6.6 Manual Suggestions: Child Seat Manual...........................................................................35
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`3.6.7 Child Seat Installation: Lower Anchors.............................................................................37
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`3.6.8 Child Seat Installation: Loose Installation.........................................................................37
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`3.6.9 Recline Error......................................................................................................................37
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`3.6.10 Routing Error .....................................................................................................................38
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`3.6.11 Twisted Lower Anchor Straps ...........................................................................................38
`
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`Recommendations..............................................................................................................39
`
`
`Future Directions ...............................................................................................................42
`
`5
`References..........................................................................................................................43
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`6
`Appendix A: Sample Child Seat Observation Form......................................................................45
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`Appendix B: Sample portions of a car manual and CRS (A) manual used by a participant .........46
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`Appendix C: Labeling differences between CRS A, B, C (clockwise from left) from
`
`studies 1-2 ..........................................................................................................................47
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`Appendix D: Example warning labels affixed the CRS A, B, C (top to bottom)..........................48
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`Appendix E: Studies 1-2 Experiment Instructions.........................................................................49
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`Appendix F: Study 3 Experiment Instructions...............................................................................50
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`Appendix G: Design Feedback Questionnaire...............................................................................51
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`List of Figures
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`Figure 1. Hierarchical Task Analysis of proper child seat installation ........................................ 2
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`Figure 2. Heuristics of vested child safety groups ........................................................................3
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`Figure 3. Child restraint systems used in studies 1-2....................................................................9
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`Figure 4. LATCH connector variations of CRS A, B, C.............................................................10
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`Figure 5. Child restraint systems used in study 3........................................................................11
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`Figure 6. Diagram of initial and completed infant CRS installation for studies 1-2
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`participants with LATCH-equipped vehicles ..............................................................14
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`Figure 7. FTA of major errors in rear-facing (RF) infant CRS installation ................................15
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`Figure 8. User decision tree example of the choices subjects make during CRS
`
`installation....................................................................................................................20
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`Figure 9. Ratings of labels and CRS instruction manuals from seat belt installation
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`participants.................................................................................................................. 23
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`Figure 10. Ratings of labels and CRS instruction manuals from LATCH installation
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`participants.................................................................................................................. 23
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`Figure 11. Diagram of initial and completed convertible CRS installations................................ 24
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`Figure 12. Study 3 convertible CRS installation times by attachment types used....................... 25
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`Figure 13. The lock-off on CRS D is a feature difference that contributed to seat belt
`
`routing misuse............................................................................................................. 28
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`Figure 14. Ratings of labels and CRS instruction manuals from convertible installation
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`participants... ............................................................................................................... 29
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`Figure 15. Reported manual or labels read by studies 3-5 participants ....................................... 33
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`Figure 16. Manual sections read by participants from studies 3-5............................................... 34
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`Figure 17. Examples of tether installation diagrams from two child seat manuals...................... 36
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`Figure 18. The usability principle of affordance can be used to associate the child seats’
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`attachment points with LATCH connectors ............................................................... 40
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`List of Tables
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`Table 1. Participant sample type by study.................................................................................... 6
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`Table 2. LATCH infant CRS installation error rates.................................................................. 16
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`Table 3. CRS comparisons during seat belt install..................................................................... 18
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`Table 4. CRS comparisons of LATCH installation errors ......................................................... 18
`
`Table 5. Loose installation error rate comparisons by seat material type .................................. 18
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`Table 6. CRS comparisons during child install.......................................................................... 21
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`Table 7. LATCH convertible CRS installation error rates......................................................... 26
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`Table 8. Convertible CRS comparisons of installation errors.................................................... 27
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`Table 9. LATCH convertible CRS installation error rates......................................................... 31
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`Table 10. Lower anchor labeling and visibility variations ........................................................... 40
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`1 Background
`
`In a Child Restraint System (CRS) misuse study sponsored by NHTSA (Decina &
`Lococo, 2004), field observations were conducted in six states where 72.6 percent of the
`3,442 CRSs displayed one or more forms of misuse. Examples of misuse were
`inappropriate CRS for the child’s age and weight, wrong CRS direction, loose
`installation, and improper placement of the CRS. The most common forms of misuse
`
`were loose harness straps when securing the child to the CRS and loose safety belts when
`securing the CRS to the vehicle. Harness retainer clip misuse was also prevalent, but not
`a severe misuse.
`
`In a following study, Decina & Lococo (2007) focused on observed misuse with CRSs
`installed with Lower Anchors and Tethers for Children (LATCH) for 1,000 children less
`than 5 years of age. Approximately one-third of the drivers used the vehicle safety belt to
`attach the CRS despite the fact that LATCH was available in the seating position
`occupied by the child. Drivers who did not like using LATCH responded that they had
`difficulty with releasing from bars, hooking to bars, tightening, and difficulty seeing and
`finding the bars. Loose installation where the CRS moved more than one inch from side-
`to-side constituted 30 percent of observed misuse.
`
`Previous studies (Rudin-Brown et al., 2004; Rudin-Brown et al., 2003) have reported
`comparatively higher difficulty with rear-facing child seat installations. Rudin-Brown
`(2004) noted that participants often had a strong tendency to install the CRS into the
`vehicle in the forward-facing direction despite the labels affixed to the child seat that
`specified infants to be installed rear-facing. Rudin-Brown and her colleagues found that
`optimal labels located in the front and back of the CRS with a pictogram and text
`improved task compliance levels to 50 percent. They also recognized that CRS
`installation experience level and label location were factors in label compliance.
`Additionally, external factors such as misconceptions leading subjects to believe a child
`is safe facing forward should be considered when designing instructions and labels for
`parents and caregivers.
`
`If drivers were aware that their installation was incorrect, they may seek help to fix the
`
`problems. However, drivers may not know that the CRS installation was incorrect. The
`level of disconnect between the participant’s assessment on a child seat installation is
`noted in studies showing high confidence levels despite mistakes made. In a report by
`National Safe Kids Campaign (NSKC), 96 percent of parents believed they installed their
`child seat correctly. However, data from child seat checkup stations consistently show
`that four out of five participants unintentionally made potentially hazardous installation
`mistakes (Decina & Knoebel, 1997; 1996; National Safe Kids Campaign, 2004).
`
`Installation problems occur because child restraint systems are known to be complicated
`to install due to such factors as confusing child seat design, vehicle design, and
`instructions. In order to be effective, child restraint systems must be installed correctly.
`CRS misuse is important to correct because a correct installation can reduce the risk of
`
`fatal injury by 71 percent and hospitalization by 67 percent (Kahane, 1986).
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` Figure 1. Hierarchical Task Analysis of proper child seat installation.
`
`A CRS installation is complicated because of the numerous steps involved in achieving a
`proper fit with a vehicle and securing the child in the CRS. To examine the complexity
`of installing a CRS, a Hierarchical Task Analysis (HTA) was performed to document all
`the steps necessary to properly restrain a child. This framework is used to understand
`installation requirements and for identifying areas that need improvement. The goal of
`correctly installing a CRS requires the completion of four main sub-tasks: preparing the
`vehicle, preparing the child seat, performing the CRS installation, and checking the
`installation after completion (See Figure 1). Each sub-goal is comprised of operations
`that can be further broken down into smaller tasks. Because it is necessary for
`participants to complete each sub-task, mistakes that stem from any operation may lead to
`installat