**1. Introduction**

In the past decades extensive research and development (R&D) has made for effective protection of the occupants in conventional vehicles. Through analytical and experimental investigations on the kinematics response and injuries of postmortem human subject (PMHS) in forward-facing seating under different frontal, oblique, side, and rear impacts, the injury measures and criteria for the trauma of each body region at Abbreviated Injury Scale (AIS) with the injury risk probability function have been defined. The families of the anthropomorphic test devices (ATDs) have been developed as the laboratory test tools for surrogate human occupants representing a population of different gender and ages. These ATDs included advanced THOR dummies for the 50th%ile adult male and 5th%ile female and Hybrid-III dummies for 95th%ile and 50th%ile adult males, 5th%ile female, 10 year old, 6 year-old, 3 year-old, and 1 year children, mainly for the frontal impact applications; WorldSID, Eurosid, US-Sid dummies of the 50th%ile male and 5th%ile female for the side impacts; and BioRid dummy for the rear impacts. Dummy based measures and criteria for the human body injuries have been developed from the paired studies of the PMHS tests and dummy tests at laboratory impact test conditions.

Based on the research and development, the government regulatory crash tests and evaluation standards known as New Car Assessment Programs (NCAP) and other motor safety regulations have been implemented in industry for nearly three decades, mainly for occupant protection of the forward-facing seated occupants in conventional vehicles, including the first-row driver and passenger and the second-row occupants, for vehicle frontal, side and rollover crashes. It was estimated to have saved hundreds of thousands of lives in the field each year [1].

As new automated vehicles technologies are accelerating in recent years, the National Highway Traffic Safety Administration (NHTSA) [2] released new federal guidance for Automated Driving Systems (ADS) on September 12, 2017, prioritizing occupant safety with the vision for safe deployment of automated vehicle technologies to a future with fewer traffic fatalities and increased mobility for all occupants. The new guidance supports further development of this important new technology, and offers a voluntary guidance for twelve priority safety design elements of the ADS, including new occupant protection systems that provide enhanced protection to occupants of all ages and sizes, additional countermeasures that will protect all occupants in any alternative planned seating or interior configurations, and the tools to demonstrate such due care not only limited to physical testing but also including virtual tests with vehicle and human body models.

Automated vehicles (AV) will pose challenges and opportunities for occupant protection since an AV could involve in different crash conditions, occupants could be from more diverse population, and seating arrangements could be free of restriction.

Recent trends in AV interior seating configurations bring more innovative and versatile design options than the conventional vehicles. In additional to the traditional forward-facing seats, AV seating designs may consider oblique-facing, rear-facing, and side facing or any other angle-oriented seating positions. The occupant postures in an AV could also vary at great extent, from normal seated to leaning backward until lying down. Jorlöv et al. [3] investigated user desires and attitudes to seating positions and activities in future highly automated cars. The survey found that during long drives, with several occupants in the car, there is a desire to rotate the seats to a living room position. During shorter drives alone, users would prefer to maintain the forward-facing position, but with the seat reclined to a more relaxed position.

For effective protection to all occupants of all ages and sizes in any alternative planned seating or interior configurations from various vehicle crashes, it is necessary for us to understand better the kinematics and injury patterns and outcomes of AV occupants at new seating configurations, and to develop better biofidelic tools and occupant injury evaluation methods.

In the past several years some fundamental biomechanics research has been performed on the PMHS and dummies in oblique facing, rear facing, and side-facing seating positions and reclined postures. Jason et al. [4] studied kinematic occupant responses and injury outcomes from 3-point seatbelt restrained PMHS in a forwardfacing seat subjected to lateral and oblique far-side vehicle crash pulses of 6.6 mph and 14 mph. Humm et al. [5] studied kinetic and kinematic occupant responses, and injury outcomes from the lap-restrained PMHS in the oblique and side-facing seats subjected to a frontal pulse with 16 g peak, 13.4 m/s (48 km/h or 30 mph) change in velocity, and 90 ms rise time (USCFR-1988) in an aviation environment. The sustained injuries included spinal injuries for all subjects varying with vertebral level, rib fractures, pelvic injuries, and leg injuries. Kang et al. [6, 7] studied kinematic responses and injury outcomes from the 3-point seatbelt restrained PMHS in the rear-seats subjected to frontal pulses of 16 mph, 24 mph and 35 mph crash severities of a represented vehicle. Minor c-spine injuries and transverse process fractures, 3–15 ribs fractures were observed from the PMHS at the rear seat under the 35 mph crash pulse. More injuries (Clavicle, scapula, and pelvis fractures) were observed from the PMHS at same test condition with the reclined 45 deg. seating.

Good progress has also been made in development of omni-directionally biofidelic human body models (HBMs). In the past decades, several finite element human body models for the occupants and pedestrians have been developed worldwide. Most recently, Global Human Body Model Consortium (GHBMC) have developed a family of HBMs in total of 13 models representing the 95th%ile and 50th%ile male and 5th% ile female occupants and pedestrians, and a six-year old child pedestrian. Biofidelity of the GHBMC 50th%ile male detailed occupant model (M50-O v4.5) was evaluated for the responses to the UVA PMHS farside sled tests condition [8], as well as to the rear impact sled tests by Kang et al. [9]. These results indicated better biofidelity of the HBMs than the dummies at these conditions.

In this research, we have used the GHBMC HBMs as a tool for assessment of the occupant kinematics and injuries, and for evaluation of the restraint performance.

The objectives of this research were the following


In this chapter, Section 2 summarizes the GHBMC HBM validations and the occupant injury risk assessment methods. Section 3 states the occupant injury analysis for the seating in various 360 degree orientated seating positions. Section 4 focuses on the occupant injury analysis for the side-facing seat occupant. Section 5 demonstrates the evaluation methods and results for new restraint concepts for protection of the side-facing seat occupants.
