Feasibility of center LATCH

Period Covered: October 2012-July 2013This paper explores the geometric feasibility of installing dedicated lower anchors in the center rear seating positions of vehicles. Analysis was based on a previous research study in which the lateral spacing of seat belt and LATCH lower anchorages were measured in 85 model year 2010-2011 vehicles. The goal of this study was to determine how many vehicles would have the physical space to incorporate a third set of dedicated lower anchors in the center seating position for child restraint installation. Usability of all of the lower anchors, as well as the seat belts, was also considered. To begin, nine vehicles that currently have dedicated lower anchors in the center position were reviewed. The distances between all seat belt anchors and lower anchors across the vehicle sample were also analyzed to identify spacings that are currently feasible in production. The arrangement of seat belt and lower anchor hardware across the rear seat was also reviewed with respect to usability. Based on these analyses, a lateral distance between the outboard webbing and outboard lower anchor of 75 to 100 mm is common. The suggested minimum distance between lower anchors and seat belt hardware is 25 mm. Based on these dimensions, vehicles with 710 mm or more between the outboard lower anchor centerlines (OBLACL) should have sufficient space to provide three sets of usable, dedicated lower anchors in the right, center, and left seating positions. Providing the highest level of usability with regard to use of seat belt or LATCH hardware in adjacent seating positions would be achieved by placing each pair of lower anchors between the webbing and buckle hardware for the seating position. If the OBLACL is less than 710 mm, an improvised center LATCH position (permitting use of the inboard lower anchors from the outboard seating positions to secure a child restraint in the center seating position) may be feasible. The maximum spacing of this improvised center LATCH position would be 480 mm. If a vehicle allowed an improvised center LATCH position, placing the inboard lower anchor between the outboard buckle and nearest center seat belt hardware would maximize usability of the seat belt in the outboard seating position and lower anchors in the center seating position.National Highway Traffic Safety Administration U.S. Department of Transportationhttp://deepblue.lib.umich.edu/bitstream/2027.42/111831/1/103191.pd

Tether Anchors in Pickup Trucks: Assessing Usability, Labeling and Performance

Technical Report FinalThis project investigated factors relating to tether use and misuse in pickup trucks and evaluated four interventions designed to educate consumers on proper use. The dynamic performance of four tether locations was also evaluated. Volunteer testing was performed with 24 subjects on 4 different pickup trucks using 2 forward-facing child restraints (Britax Marathon G4.1 and the Evenflo Triumph), with each subject performing 8 child restraint installations on the set of four vehicles. Pickup trucks were selected to represent four different implementations of tether anchors in pickup trucks: Chevy Silverado (plastic wire loop routers), Dodge Ram (webbing routers), Nissan Frontier (back wall anchor), and Toyota Tundra (webbing routers plus metal anchor). Interventions included a diagram label, QR code linked to video instruction, coordinating (i.e., low contrast with interior trim) text label, and contrasting-color text tag. Subjects used the tether in 93% of trials. However, tether use was completely correct in only 9% of trials. The installation was considered functional if the subject attached the tether to a tether anchor and had a tight installation (ignoring routing and head restraint position); 28% of subjects achieved a functional installation. The most common error was attaching the tether anchor to the anchor/router directly behind the child restraint rather than placing it through the router and attaching it to the anchor in the adjacent seating position. The Nissan Frontier, with the anchor located behind the seatback, had the highest rate of correct installations but also had the highest rate of attaching to components other than a tether anchor (seat adjustor, child restraint hardware, head restraint). None of the interventions had a significant effect on correct installation; not a single subject scanned the QR code to access the video instructions. The most successful subjects spent extensive time reviewing the vehicle manuals. Results indicate that current implementations of tether anchors in pickup trucks are not intuitive and alternate designs should be explored. A set of impact tests was run using the proposed FMVSS No. 213 bench to evaluate the dynamic performance of the different tether anchor locations used in the subject testing, with and without 50 mm of slack. A tether anchor location simulating a roof-mounted location above the rear window of a pickup was also included in the matrix. Slack had a greater effect on head excursion compared to tether anchor location. Tether anchors located on the seatback, filler panel, or at an adjacent seating position had the lowest head excursions, followed by an anchor located above the window, followed by no tether anchor. Future research should involve testing performance of a tether anchor located above the window after being placed through a tether routerInsurance Institute for Highway Safetyhttps://deepblue.lib.umich.edu/bitstream/2027.42/156027/1/UMTRI-2016-30.pdfDescription of UMTRI-2016-30.pdf : Technical Report Fina

LATCH usability in vehicles

This project investigated the usability of Lower Anchors and Tethers for CHildren (LATCH) hardware by measuring LATCH implementations in 98 2011 or 2010 model-year vehicles. ISO and SAE LATCH usability rating systems were used to assess all vehicles using data from the second row left position. Child restraint/vehicle interaction was assessed using both ISO and NHTSA proposed procedures. Volunteer testing was performed with 36 subjects on 12 different vehicles using 3 different child restraints, with each subject performing 8 child restraint installations. The results from the vehicle survey indicate that most vehicle manufacturers provide LATCH hardware at only the minimum number of locations required by FMVSS 225. Only 7 vehicles had three sets of LATCH hardware in the second row, while most of the remaining 91 vehicles were only equipped with LATCH in each outboard position and a tether anchor in the center position. In the 21 vehicles with a third row, four had no tether anchors and 11 had no lower anchors in the third row. The SAE child restraint fixture could not be installed in 27 vehicles, although head restraint interference was the cause of interference in only one vehicle. Fifty-nine vehicles met the SAE recommended lower attachment force of 75 N (16.9 lb) or less, while 15 vehicles required forces from 2 to 8 times this value. Only 2 vehicles met SAE recommendations for clearance angle of at least 75 degrees around the lower anchors. The depth of the lower anchors relative to the bight is less than 2 cm in 28 vehicles, 2-4 cm in 34 vehicles, and greater than 4 cm in 36 vehicles. The most common location for the tether anchor is the seatback (42) and package shelf (35). The lower anchors are marked in 77 vehicles, while the tether anchors are marked in 68 vehicles. Only Ford products clearly specify weight ranges for use of LATCH hardware in their manuals. Many vehicle manuals are not clear on how the head restraint should be positioned during child restraint installation. ISO ratings of vehicle LATCH usability ranged from 41% to 78%, while vehicles assessed using the SAE draft recommended practice met between 2 and all 10 of the recommendations. There was a slight correlation between vehicles meeting SAE recommended practices and ISO usability ratings. Twenty vehicles with a range of vehicle features were assessed using the ISO vehicle/child restraint form and 7 child restraints; ISO vehicle/child restraint interaction scores ranged from 14% to 86%. Based on these interaction scores, the Cosco Alpha Omega, the Chicco KeyFit, and Evenflo Maestro were used with a subset of 12 vehicles to perform volunteer testing and assess the quality of subject installations. No vehicle factors predicted tether use or correct use of tether. However, the correct use of lower anchors was associated with a lower anchor clearance angle greater than 54°, an attachment force of 40 lb or less, and lower anchor depth within the bight of less than 2 cm. Correct lower anchor use also had 3.3 times higher odds of tight installation compared to incorrect use.Insurance Institute for Highway Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/90856/1/102854.pd

Optimizing protection for rear seat occupants: assessing booster performance with realistic belt geometry using the Hybrid III 6YO ATD

A series of sled tests was conducted to examine the performance of booster seats under belt geometries representing the range found in the rear seats of current vehicles. Twelve tests were performed with the standard 6YO Hybrid III ATD and 29 tests were performed with a modified version of the 6YO ATD. The modified dummy has a pelvis with more realistic shape and flesh stiffness, a gel abdomen with biomechanically-based stiffness characteristics, and a custom neoprene jacket. Shoulder belt upper anchorage was set at the FMVSS No. 213 belt anchorage location and 64 mm inboard and outboard from this location. Lap belt anchorage locations were chosen to span the range of lap belt angles permitted under FMVSS 210, using the FMVSS No. 213 belt anchorage locations and forward belt anchorage locations that produce a much steeper lap belt angle. Four booster seats that provide a range of static belt fit were used. The ATDs were positioned using either the standard FMVSS No. 213 seating procedure or an alternate UMTRI procedure that produces postures closer to those of similar-size children. Kinematic results for the standard and modified dummies under the same test conditions were more similar than expected. The current version of the modified 6YO is less sensitive to lap belt geometry than the prototype version of the dummy. The seating procedure had a greater affect on kinematic results. The UMTRI seating procedure produced greater knee-head excursion differences and less forward torso rotation than the FMVSS No. 213 procedure. Shifting the shoulder belt upper anchorage 128 mm laterally produced minimal variations in kinematics for a given booster seat/lap belt condition, likely because the belt-routing features of the booster seats limited the differences in static shoulder belt score to less than 10 mm. Moving the lap belt geometry from rearward (shallow angle) to forward (steep angle) produced less desirable kinematics with all booster seats tested. The forward position of the lap belt anchorage allows greater forward translation of the booster and ATD before the belt engages the pelvis. Steeper belt angles are associated with better lap belt fit for children sitting without boosters, so designing rear seat belts for children who sit with and without boosters may involve a performance tradeoff.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/90973/1/102860.pd

Effects of vehicle features on CRS installation errors

This report documents a study of how vehicle features contribute to CRS installation errors. Thirty-two subjects were recruited based on their education level (low or high) and experience with installing CRS (none or experienced). Each subject was asked to perform four child restraint installations in three vehicles. Each subject first performed a CRS installation with a seatbelt in one vehicle, followed by three CRS installations using LATCH, one in each of three vehicles. One child restraint with a hook-on LATCH connector and one with a push-on LATCH connector were used. All installations were forward-facing, using an 18-month-old CRABI anthropomorphic test device (ATD). Six vehicles were used in testing, with half of subjects testing with each vehicle. Conditions were selected to provide a range of LATCH locations (visible, above seating surface, buried in bight), buckle stalk types (webbing vs. rigid), and tether locations (package shelf vs. seatback). After each installation, the experimenter evaluated 28 factors for each installation (such as tightness of installation, tether tightness, and LATCH belt attached correctly). Analyses used linear mixed models to identify the CRS installation outcomes associated with vehicle features. For LATCH installations, vehicles requiring higher forces to attach connectors to lower anchorages were more likely to be attached incorrectly. Vehicle seats with a bightline waterfall (which places the lower anchorage above the seating surface) increased rates of tight CRS installation for both seatbelt and LATCH installs. Seatbelt installations were tight (and locked) more frequently when the buckle stalk was located close to the bight rather than further forward. Subjects used the tether correctly in 30% of installations. Subjects used the tether more frequently during LATCH installations compared to seatbelt installations. The tether was used more frequently in sedans (with anchorage locations on the package shelf) than in vehicles with the tether anchorage located on the seatback. However, when the tether was used, it was routed correctly more often in vehicles with the tether anchorage on the seatback. A tether wrap around distance of 210 mm was sufficient to allow tightening of the tether with the two CRS tested, but additional testing showed that 5/16 CRS could not be tightened sufficiently with this wrap around distance. Installation time decreased with successive trials, but installation time was longer when subjects used the vehicle or CRS manuals. Subjects used the vehicle manual in 38% of installations, and were more likely to do so when the tether anchorage was located on the vehicle seatback. Subjects used the CRS manual in 88% of installations. In questionnaire responses, subjects indicated that the head restraints affected installations, and vehicle manuals varied in their ease of understanding. They also noted that tether anchorages on seatbacks were more difficult to locate than those on the package shelf. Results from this study do not fully support SAE and ISO recommendations for LATCH usability in vehicles. Recommendations areVTTI, National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89862/1/102796.pd

Effect of Tether Routing and Anchor Location on Child Restraint Kinematics

Technical ReportA series of 16 sled tests were performed to examine the effect of tether routing with respect to the vehicle head restraint on the kinematics of the Hybrid III 3-year-old ATD secured in two forward-facing harnessed child restraints. The main outcome of interest was whether a particular tether routing provided a safety benefit by reducing head excursions. Two different child restraints were used, one with a single strap tether and the other with a V-style tether. The single strap was routed either under or over the head restraint, while the V-style tether was routed either under or around the head restraint. Three different tether anchor locations were evaluated, representing locations on the roof, rear filler panel, or the lower vehicle seat-back. Two different vehicle seats were mounted to the FMVSS 213 sled buck. One was the outboard second-row seat from the 2011 Ford Explorer, while the other was the center second-row seat from the 2011 Jeep Grand Cherokee. Child restraints were installed with lower anchors in the Explorer seat and the seatbelt in the Grand Cherokee. The specific tether routing did not have an effect on head excursion. Rather, head excursion increased as the length of tether webbing between the tether attachment point on the child restraint and the tether anchor hardware increased. The results of these tests suggest that the tether routing providing the shortest distance to the vehicle tether anchor be recommended, as long as that routing allows the user to achieve a tight tether installation. This study is limited by the use of only two different vehicles and two different child restraints for testing.National Highway Traffic Safety Administrationhttps://deepblue.lib.umich.edu/bitstream/2027.42/149101/1/UMTRI-2013-27.pdfDescription of UMTRI-2013-27.pdf : Technical Repor

Assessment of ATD Selection and Use for Dynamic Testing of Rear-Facing Child Restraint Systems for Larger Infants and Toddlers

Technical ReportThis report documents a test series that explored methods for using currently available child anthropomorphic test devices (ATDs/crash test dummies) to dynamically evaluate child restraint systems (CRS) for children more than 1 year old facing rearward in motor vehicles. These CRS are more typically rear-facing convertible seats but also can be infant-only rear-facing seats. The study evaluated five installation methods using the Hybrid III 3-year-old ATD and the CRABI 18- month-old ATD. Three child restraint system models were evaluated using the current FMVSS No. 213 test bench. None of the ATD conditions produced a systematic change in the dynamic response criteria evaluated by FMVSS No. 213, but some methods were easier to implement in the laboratory. The report documents each method and their potential advantages and disadvantages.National Highway Traffic Safety Administrationhttps://deepblue.lib.umich.edu/bitstream/2027.42/149100/1/UMTRI-2014-12.pdfDescription of UMTRI-2014-12.pdf : Technical Repor

Comparing the CRABI-12 and CRABI-18 for Infant Child Restraint System Evaluation

Technical Report FinalA preliminary study was performed to consider how evaluation of rear-facing-only child restraints might differ if the CRABI 18 month old crash test dummy was used instead of the CRABI 12 month old. In comparison to child anthropometry data, the CRABI-18 does a better job in representing the dimensions of children over 1 year old. Nineteen rear-facing-only child restraint systems (CRS) were measured, and both test dummies were installed in the CRSs for static evaluation. The CRABI-12 fit well in all the CRSs. Nine child restraints were too narrow for the CRABI-18 shoulders (including 7 CRSs for use with children at or over 18 kg [30 lb]), and 12 child restraints did not allow the recommended 25 mm head clearance. In dynamic FMVSS No. 213 testing with 3 CRSs (Graco Snugride30, Chicco KeyFit, and Evenflo Embrace), the measured response of both test dummies was similar; both met all FMVSS No. 213 requirements.National Highway Traffic Safety Administrationhttps://deepblue.lib.umich.edu/bitstream/2027.42/154007/1/UMTRI-2013-5.pd

Factors affecting tether use and misuse

This project investigated factors relating to tether use and misuse. Volunteer testing was performed with 37 subjects on 16 different vehicles using 2 forward-facing child restraints (Britax Marathon 70 or the Evenflo Triumph), with each subject performing 8 child restraint installations on a set of four vehicles. Vehicles were selected to provide a variety of general tether locations (filler panel, upper seatback, lower seatback, floor, or roof), as well as a variety of recommended tether routings with respect to the head restraint: under, over, around. Simple instruction regarding the LATCH system was provided after the fourth trial. Subjects used the tether in 89% of the 294 forward-facing trials and attached the tether correctly in 57% of installations. Subjects were more likely to use the tether if they were less than age 40, had previous tether experience, if the tether was located on a filler panel, and if the vehicle did not have any potentially confusing hardware. In addition, tether use was 83% in the first four trials and increased to 95% in the last four trials after instruction was provided. Subjects had the greatest difficulty in the pickup truck, which use loops of webbing as a router for the installed position and the tether anchor for the adjacent position; the tether was attached correctly in only 11 percent of installations. Tethers were more likely to be used when the tether anchor was located on the filler panel of sedans, which had a use rate of 95 percent, compared to when the anchor was located on the floor, roof, or seatback, which had use rates ranging from 79 to 89 percent. Tethers were less likely to be attached correctly when there was potentially confusing hardware present, 47 percent, compared to 70 percent. In addition, tether anchors located on the filler panel or mid seatback had higher rates of correct attachment, 60 and 69 percent , respectively, than those on the floor, roof, or lower seatback, which all had correct attachment rates lower than 50 percent . No vehicle tether hardware characteristics or vehicle manual directions were associated specifically with correct tether routing and head restraint position. Installations involving the single tether strap were 10 times as likely to have the tether attached correctly and 1.7 times as likely to be routed correctly and have the head restraint positioned correctly, compared with installations with the v-shaped tether. Lack of instruction in most vehicle owner’s manuals regarding the routing of a V-style tether more challenging to use. With the single strap-style tether, it was more straightforward to have the tether strap flat and pull it tight, as well as to route it as directed. With the V-style tether, the adjustment hardware was often located underneath or close to the head restraint when installed in the vehicle, making it difficult to tighten. Recommendations to reduce tether misuse include labeling tether anchors, eliminating confusing hardware, allowing any head restraint position (including removal), providing instruction for routing V-style tethers, allowing options in tether routing, and redesigning tether anchors/routers found in pickup trucks.Insurance Institute for Highway Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/106031/1/102990.pd

Subject Evaluation of Devices Intended to Reduce Risk of Seatbelt Entanglement

Since 2000, there have been over 200 incidents reported where a rear seat occupant became entangled in the seatbelt when they inadvertently switched it from emergency locking mode (ELR) to automatic locking mode (ALR). While a method is needed to lock the seatbelt when using it for child restraint system (CRS) installation, the National Highway Traffic Safety Administration (NHTSA) commissioned tool, inc. to develop prototype devices that could reduce the risk of seatbelt entanglement resulting from the lockability requirement. The purpose of this study is to perform testing with volunteer subjects to evaluate these prototype devices in comparison to standard seatbelt system by assessing how different designs would be used to install CRS, the quality of the resulting installations, how users would disentangle a trapped child surrogate, as well as to identify volunteer experience when using the belts themselves. Four prototype devices were evaluated in two phases of testing. In phase 1, D1, D2, and D3 were compared to standard seatbelt and LATCH using two forward-facing and two rear-facing CRS. In phase 2, D1 and D4 were compared to standard seatbelt using three forward-facing CRS. Phase 1 tested 16 subjects while Phase 2 tested 24. Subjects were recruited to include men and women of different ages with and without previous CRS installation experience; phase 1 also included education level as a criteria, while phase 2 included subject size. After the first installation trial using each device, the subject was presented with a crash dummy entangled in same device belt system, and instructed to free the dummy. In phase 2, subjects also participated in “comfort” trials where they sat in the vehicle seat, donned the seatbelt, and performed a reaching task intended to trigger a nuisance locking scenario. All four prototype devices had shorter disentanglement times than trials with the standard seatbelt, but there was not a statistically significant difference between the devices. There were no substantial differences in the quality of child restraint installation among the prototype devices. In phase 2, subjects viewed video instructions midway through the installation trials, which had a strong effect on reducing installation errors. In nuisance locking trials, subjects with higher BMI or taller stature were most likely to experience unintended seatbelt locking while performing a reach task.Tool, Inc.http://deepblue.lib.umich.edu/bitstream/2027.42/170921/1/UMTRI-2018-7.pdfDescription of UMTRI-2018-7.pdf : Technical Report FinalSEL