Occupant Protection in Rear-end Collisions: I. Safety Priorities and Seat Belt Effectiveness

James, Michael B.; Strother, Charles E.; Warner, Charles Y.; Decker, Robin L.; Perl, Thomas R.

doi:10.4271/912913

Cited by 24 publications

(2 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It reflected the yielding behavior of seat designs of the 1970s-90s, which showed good field performance in rear crashes (Malliaris, 1990;James et al, 1991;Digges & Malliaris, 1993). However, it became clear that there were shortcomings by allowing the occupant to rotate the seatback rearward in severe rear crashes, since there could be a loss of occupant retention and the energy transfer capability was limited.…”

Section: Evolution Of Yielding Seatsmentioning

confidence: 93%

“…This kinematic is similar to diving injuries seen in shallow water with head impact and the body continuing forward causing a flexion-compression injury. However, this injury is rare, and the overall safety performance of 1970-90s yielding seats has been shown to be good in various studies of rear crashes (Malliaris, 1990;James et al, 1991;Digges & Malliaris, 1993). Even the NASS estimates in Table I reflect a high degree of safety in rear crashes with a 27% incidence of AIS 1 and 0.065% of AIS 3+ cervical injury.…”

mentioning

confidence: 87%

See 1 more Smart Citation

Influence of Seat Properties on Occupant Dynamics in Severe Rear Crashes

Viano¹

2003

Traffic Injury Prevention

View full text Add to dashboard Cite

Seat performance in retaining an occupant, transferring energy, and controlling neck responses is often questioned after severe rear crashes when fatal or disabling injury occur. It is argued that a stiffer seat would have improved occupant kinematics. However, there are many factors in occupant interactions with the seat. This study evaluates four different seat types in 26 and 32 mph (42 and 51 km/h), rear crash delta Vs. Two seats were yielding with k = 20 kN/m occupant load per displacement. One represented a 1970s yielding seat with j = 3.4 degrees /kN frame rotation per occupant load, and 3 kN maximum load (660 Nm moment), and the other a high retention seat phased into production since 1997 with j = 1.4 degrees /kN, and 10 kN maximum load (2200 Nm). Two seats were stiff with k = 40 kN/m. One represented a 1990s foreign benchmark with j = 1.8 degrees /kN and a 7.7 kN maximum load (1700 Nm), and the other an all belts to seat (ABTS) with j = 1.0 degrees /kN and 20 kN maximum load (4400 Nm). The crash was a constant acceleration of 11.8 g, or 14.5 g for 100 ms. Occupant interactions with the seat were modeled using a torso mass, flexible neck and head mass. By analysis of the equations of motion, the initial change in seatback angle (Deltatheta) is proportional to jk(y - x), the product jk and the differential motion between the vehicle (seat cushion) and occupant. The transition from 1970s-80s yielding seats to stronger seats of the 1990s involved an increase in k stiffness; however, the jk property did not change as frame structures became stronger. The yielding seats of the 1970s had jk = 68 degrees /m, while the stiff foreign benchmark seat had jk = 72 degrees /m. The foreign benchmark rotated about the same as the 1970s seat up to 50 ms in the severe rear crashes. While it was substantially stronger, it produced higher loads on the occupant, and the higher loads increased seatback rotations and neck responses. The ABTS seat had the lowest rotations but also caused high neck responses because of the greater loads on the torso. Neck displacement (d) is initially proportional to (k/m(T)) integral integral y, seat stiffness times the second integral of vehicle displacement divided by torso mass. As seat stiffness increases, head-torso acceleration, velocity, and neck displacement increase. This study shows that the jk seat property determines the initial seatback rotation in rear crashes. If a stronger seat has a higher stiffness, it rotates at higher loads on the occupant, reducing the overall benefit of the stronger frame, while increasing neck responses related to whiplash or neck extension prior to subsequent impacts. The aim of seat designs should be to reduce jk, provide pocketing of the pelvis, and give head-neck support for the best protection in severe rear crashes. For low-speed crashes, a low k is important to reduce early neck responses related to whiplash.

show abstract

Section: Evolution Of Yielding Seatsmentioning

confidence: 93%

mentioning

confidence: 87%

Influence of Seat Properties on Occupant Dynamics in Severe Rear Crashes

Viano¹

2003

Traffic Injury Prevention

View full text Add to dashboard Cite

show abstract

Analysis of human body dynamics in simulated rear-end impacts

Huang¹

1998

Human Movement Science

View full text Add to dashboard Cite

Rebound After Rear Impacts

Viano¹,

Parenteau²,

Burnett

2013

Traffic Injury Prevention

View full text Add to dashboard Cite

ABTS seats remain more upright in rear-end crashes and transfer greater load to the occupant during rebound than conventional seats that yield rearward and absorb energy in higher severity crashes. Rebound occurs earlier and at higher velocities with ABTS. This displaces the occupant toward the front interior. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

show abstract

Occupant Protection in Rear-end Collisions: I. Safety Priorities and Seat Belt Effectiveness

Cited by 24 publications

References 4 publications

Influence of Seat Properties on Occupant Dynamics in Severe Rear Crashes

Influence of Seat Properties on Occupant Dynamics in Severe Rear Crashes

Analysis of human body dynamics in simulated rear-end impacts

Rebound After Rear Impacts

Contact Info

Product

Resources

About