Johan Ivarsson

Influence of vehicle body type on pedestrian injury distribution

Pedestrian impact protection has been a growing area of research over the past twenty or more years. The results from many studies have shown the importance of providing protection to vulnerable road users as a means of reducing roadway fatalities. Most of this research has focused on the vehicle fleet as a whole in datasets that are dominated by passenger cars (cars). Historically, the influence of vehicle body type on injury distribution patterns for pedestrians has not been a primary research focus. In this study we used the Pedestrian Crash Data Study (PCDS) database of detailed pedestrian crash investigations to identify how injury patterns differ for pedestrians struck by light trucks, vans, and sport utility vehicles (LTVs) from those struck by cars. AIS 2+ and 3+ injuries for each segment of vehicles were mapped back to both the body region of the pedestrian injured and the vehicle source linked to that injury in the PCDS database. The findings indicate that the head is the most frequently injured body region for both vehicle segments, but the lower extremity is second for cars, whereas the torso is second for LTVs. Mapping the injuries back to the vehicles we find that the most frequent sources of injury for cars are the windshield and bumper, while for the LTVs it is the hood and hood leading edge.

The influence of age on the morbidity and mortality of pedestrian victims

Objectives. The present study examined the influence of age on the morbidity and mortality of pedestrian victims while controlling for confounding factors. Methods. The Pedestrian Crash Data Study (PCDS) database was used for a cross-sectional study to compare the outcome of senior (age ≥60 years) and adult (age 19 to 50 years) pedestrian victims. The outcome measures were the Injury Severity Score (ISS), Maximum Abbreviated Injury Score (MAIS), Abbreviated Injury Scale (AIS), and Mortality. Logistic regression models were used to estimate age-associated risks while controlling for confounders such as vehicle type, impact speed, and pedestrian height, weight, and gender. Results. Compared to the adult victims, the seniors had a higher average ISS (23 vs. 16, p = 0.018) and higher mortality (30 percent vs. 11 percent, p ≤ 0.001). The seniors were also more likely to have an ISS ≥9 (odds ratio = 2.72; 95 percent CI: 1.31–5.68) and to die (odds ratio = 6.68; 95 percent CI: 2.37–19.88). The seniors were approximately twice as likely to have higher AIS scores to almost every body region. Conclusions. The adjusted age-dependent risks indicated by the current study should be considered when calculating or projecting pedestrian morbidity and mortality. Adjustment in statistical models is essential to achieve precise risk estimates and in turn to appropriately allocate public health rescores.

A study of the pedestrian impact kinematics using finite element dummy models: the corridors and dimensional analysis scaling of upper-body trajectories

Pedestrian–vehicle impact experiments using cadavers have shown that factors such as vehicle shape and pedestrian anthropometry can influence pedestrian kinematics and injury mechanisms. Although a parametric study examining these factors could elucidate the complex relationships that govern pedestrian kinematics, it would be impractical with cadaver tests because of the relative expense involved in performing numerous experiments on subjects with varying anthropometry. On the other hand, finite element modelling represents a more feasible approach because numerous experiments can be conducted for a fraction of the expense. The current study examined the relationship between pedestrian anthropometry and front shape of a mid-size sedan using a PAM-CRASH model of the 50th-percentile male (50th M) Polar-II pedestrian dummy extensively validated against experimental data. To evaluate the influence of pedestrian anthropometry on response kinematics, scaled dummy models were developed on the basis of the weight and height of the 5th-percentile female (5th F), 50th-percentile female (50th F) and 95th-percentile male (95th M). Simulations of the 5th F, 50th F, 50th M, and 95th M Polar-II finite element models struck at 40 km/h by a mid-size sedan were used to generate trajectories of the head, upper thorax, mid-thorax and pelvis. In an effort to assess the validity of scaling techniques when interpreting trajectory data from vehicle–pedestrian crashes, the trajectories of the 5th F, 50th F and 95th M model were scaled to the 50th M and compared with those generated by the 50th M model. The results demonstrated non-linear behaviour of dummy kinematics that could not be accounted for with traditional dimensional analysis scaling techniques.

Design of a Full-Scale Impact System for Analysis of Vehicle Pedestrian Collisions

The complexity of vehicle-pedestrian collisions necessitates extensive validation of pedestrian computational models. While body components can be individually simulated, overall validation of human pedestrian models requires full-scale testing with post mortem human surrogates (PMHS). This paper presents the development of a full-scale pedestrian impact test plan and experimental design that will be used to perform PMHS tests to validate human pedestrian models. The test plan and experimental design is developed based on the analysis of a combination of literature review, multi-body modeling, and epidemiologic studies. The proposed system has proven effective in testing an anthropometrically correct rescue dummy in multiple instances. The success of these tests suggests the potential for success in a full-scale pedestrian impact test using a PMHS.

Occupant injury in rollover crashes – Contribution of planar impacts with objects and other vehicles

Planar impacts with objects and other vehicles may increase the risk and severity of injury in rollover crashes. The current study compares the frequency of injury measures (MAIS 2+, 3+, and 4+; fatal; AIS 2+ head and cervical spine; and AIS 3+ head and thorax) as well as vehicle type distribution (passenger car, SUV, van, and light truck), crash kinematics, and occupant demographics between single vehicle single event rollovers (SV Pure) and multiple event rollovers to determine which types of multiple event rollovers can be pooled with SV Pure to study rollover induced occupant injury. Four different types of multiple event rollovers were defined: single and multi-vehicle crashes for which the rollover is the most severe event (SV Prim and MV Prim) and single and multi-vehicle crashes for which the rollover is not the most severe event (SV Non-Prim and MV Non-Prim). Information from real world crashes was obtained from the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) for the period from 1995 through 2011. Belted, contained or partially ejected, adult occupants in vehicles that completed 1-16 lateral quarter turns were assigned to one of the five rollover categories. The results showed that the frequency of injury in non-primary rollovers (SV Non-Prim and MV Non-Prim) involving no more than one roof inversion is substantially greater than in SV Pure, but that this disparity diminishes for crashes involving multiple inversions. It can further be concluded that for a given number of roof inversions, the distribution of injuries and crash characteristics in SV Pure and SV Prim crashes are sufficiently similar for these categories to be considered collectively for purposes of understanding etiologies and developing strategies for prevention.

Non-Contact Area Measurement Techniques for Cross Sectional Properties of Soft Tissues

In this study, a non-contact optical three-dimensional digitization technique is described to account for area measurement problems related to soft tissue. The technique is used to generate digitized models of human knee ligaments (collateral and cruciate ligament bundles). Cross-sectional area of knee ligaments is determined by applying Green’s theorem on data obtained from the digitized models. The surface concavity features of different ligaments shown in this study signify the extent of approximation done by projection based methods. The study also reports the variation in cross-sectional shape of a ligament along its long axis, indicating the importance of deciding the appropriate cross section for stress calculation measurements.Copyright