Further investigation into the effective use of clear zones and barriers in a safe system's context on rural roads

This paper extends an exploratory study that assessed the traditional implementation of clear zones and compared their effectiveness at reducing injury severity with that provided by protective barriers. The results presented in this paper support the findings of the original study in challenging the conventional approach of pursuing wide clear zones. A sample of 132 crashes from the Centre for Automotive Safety Research’s in-depth crash investigations were analysed to determine the typical dynamics of vehicles in single vehicle run off road crashes. The mean departure angle of vehicles that drifted off the road without losing control was only 7.3 degrees while for vehicles that were out of control it was 17.6 degrees. Only three of the 18 vehicles in the cases where no fixed object was struck did not travel beyond a traditional nine metre clear zone. Simulations were performed for 15 of the cases. The cases chosen for simulation represented typical vehicle departure dynamics. Each case was simulated with the driver attempting to recover by steering input and then again with the driver employing emergency braking half a second after departing the road. These simulations revealed that it would rarely be feasible to provide a clear zone wide enough to accommodate a vehicle that has left the road out of control. Clear zones can accommodate vehicles that simply drift off the road without losing control. The simulations were also used to assess the appropriateness of barrier protection. Barrier protection has the potential to meet the requirements of a safe system. Ideally the barrier would be placed as close to the edge of road as practical to reduce the angle at which it may be struck.S. D. Doecke and J. E. Woolle

The accuracy of determining speeding directly from mass crash data and using the NSW Centre for Road Safety method

Exceeding the posted speed limit, or speeding, is generally accepted as a major cause of road crashes and in particular fatal crashes. However, the actual proportion of crashes in which one or more vehicles was speeding is not easily determined. The exact travelling speed of a vehicle prior to a crash can only be determined by detailed crash reconstruction. Such a reconstruction is considered beyond the scope of regular traffic police who record the majority of the crash data that makes up the mass crash databases such as the South Australian Traffic Accident Reporting System (TARS). It is therefore thought that speeding is underreported in the mass crash data. A method was developed by NSW to identify, from mass data, crashes that involved speeding as a factor. This method was subsequently used by other states, including South Australia. The Centre for Automotive Safety Research conducts the crash reconstructions required to determine speed as part of its at-scene in-depth crash investigation work. This paper compares the actual proportion of speeding crashes in the most recent set of at-scene in-depth crash investigation cases with that found by using the mass data and the method developed by the NSW Centre for Road Safety. It was found that the error ‘excessive speed’ recorded in the TARS database is not accurate in identifying crashes where a vehicle was speeding. The NSW Centre for Road Safety method of determining speeding in crashes was also found to lack accuracy, though it was more accurate than simply relying on the error ‘excessive speed’ in the TARS database.Doecke, S, Kloeden, C.N.http://acrs.org.au/events/acrs-past-conferences/2013-a-safe-system-the-road-safety-discussion

The safety potential of connected vehicles

Connected vehicle technology allows vehicles to send and receive information to and from one another, other road users and infrastructure. Although it is not yet available on any production vehicle, on-road trials are well under way. It is likely that connected vehicle technology will enter the market at a time when autonomous emergency braking (AEB) is becoming more common on new vehicles. The purpose of the present research was to estimate the safety benefits of connected vehicle technology in Australian conditions over and above what could be provided by AEB. The applications and limitations of connected vehicle technology were assessed by reviewing literature and consulting with a local developer of the technology. It was found that crash types that are poorly addressed by AEB such as right angle and right turn crashes and certain pedestrian crashes, are more likely to be addressed by connected vehicle applications. The safety benefits were calculated by applying a collision avoidance system model to simulations of real world crashes to determine the change in impact speed. It was found that the potential of connected vehicles to reduce crash risk is considerable, even in the presence of a sensor-based AEB system, and the uptake of such technology should be encouraged in ways that are shown to be cost effective.Doecke, S. D., Anderson, R. W. G

Vehicle age-related crashworthiness of the South Australian passenger fleet

In this report, the crashworthiness of passenger vehicles in South Australia is characterised. For this purpose crashworthiness is defined as the rate of serious and fatal crashes per crash of any severity. The relationship between this rate and the ages of passenger vehicles is used to characterise and compare the crashworthiness of the South Australian registered passenger vehicle fleet and the fleets of other Australian jurisdictions. The mean age of passenger vehicles registered in South Australia is around 11.2 years compared with 9.9 years for the entire Australian registered passenger vehicle fleet and 9.3 years for registered passenger vehicles of New South Wales. Based on these mean vehicle ages, tow-away crashes in South Australia have a 3% over-representation of seriously injured or killed drivers compared with the national average (assuming a crashworthiness decline of 2.53% per year of vehicle age). Analysis of only those vehicles that crash confirm these estimates and suggest an over-representation of 3.5%. Young drivers appear to be doubly disadvantaged in that they have a higher rate of serious and fatal crashes for a given vehicle age, and they tend to crash vehicles that are much older than the vehicles crashed by those drivers who are over 25 years of age. Despite this, the benefits of fleet renewal on average age-related crashworthiness are relatively modest and it may be more fruitful to encourage the safest new car fleet now so that road safety benefits can be realised in 10-15 years time. In the mean time, removal of impediments to younger drivers who would otherwise drive newer and safer cars could be considered.RWG Anderson, S Doecke and D Searso

A survey of bullbar prevalence at pedestrian crash sites in Adelaide, South Australia

This survey was designed to examine the proportion of vehicles fitted with bull bars in Adelaide, South Australia, at the sites where pedestrian crashes have occurred in the past. The sample was stratified to examine the prevalence in separate geographical regions of the metropolitan area of Adelaide. Survey results were combined using weights determined from the relative incidence of pedestrian crashes in the three survey strata. Overall, 8.6% of traffic was equipped with bull bars. Bull bar prevalence was much greater amongst heavy vehicles (28%), but heavy vehicles formed only a minor component of the traffic volume. The average site prevalence amongst light vehicle traffic was 7.5%. Site prevalence was lowest in the CBD (average 5.5%) and highest in the Outer Metropolitan Region (average 9.1%). Differences between the site prevalence in each region were statistically significant, and there was additional variation between sites within each region. 4WD vehicles are the most common vehicle type to have a bull bar fitted and 4WD vehicles with bull bars are twice as prevalent at the sites of crashes as the next most common type of bull bar equipped vehicle, work utilities.R. W. G. Anderson, G. Ponte, S. Doeck

The potential of autonomous emergency braking systems to mitigate passenger vehicle crashes

This paper details part of a research program conducted to examine the potential effect of autonomous emergency braking (AEB) systems on common crash types that involve a frontal collision. To accomplish this, simulations were conducted of 103 real world crashes. AEB system models with differing specifications were applied to these simulations to determine the change in impact speed that various AEB interventions could produce. It was found that AEB systems have the potential to reduce the impact speed, and hence the severity, in pedestrian crashes, right turn crashes, head on crashes, rear end crashes and hit fixed object crashes. The greatest potential reductions were for pedestrian crashes, head on crashes and rear end crashes. The variations in system specification demonstrate the advantages of a longer time-to-collision and higher autonomous deceleration. A system that has less potential to generate false alarms than the other systems was considered and demonstrated potential for reducing the impact speed in pedestrian, head on, rear end and hit fixed object crashes.S.D. Doecke, R.W.G. Anderson, J.R.R. Mackenzie and G. Pont

A conformational variant of p53 (U-p53AZ) as blood-based biomarker for the prediction of the onset of symptomatic Alzheimer\u27s disease

BACKGROUND: Ongoing research seeks to identify blood-based biomarkers able to predict onset and progression of Alzheimer\u27s disease (AD). OBJECTIVE: The unfolded conformational variant of p53 (U-p53AZ), previously observed in AD individuals, was evaluated in plasma samples from individuals participating in the Australian Imaging, Biomarkers and Lifestyle (AIBL) cohort for diagnostic and prognostic assessment, validated on a neuropsychological-based diagnosis, over the course of six years. DESIGN: Retrospective Longitudinal Prognostic biomarker study. SETTING: Single-center study based on the AIBL cohort. PARTICIPANTS: 482 participants of the AIBL cohort, aged 60-85 years, without uncontrolled diabetes, vascular disease, severe depression or psychiatric illnesses. MEASUREMENTS: The AlzoSure® Predict test, consisting of immunoprecipitation (IP) followed by liquid chromatography (LC) tandem mass spectrometry (MS/MS), was performed to quantify the AZ 284® peptide as readout of U-p53AZ and compared with an independent neuropsychological diagnosis. The amyloid load via amyloid β-positron emission tomography (Aβ-PET) and supporting clinical information were included where possible. RESULTS: U-p53AZ diagnostic and prognostic performance was assessed in both time-independent and time-dependent (36, 72 and 90 months following initial sampling) analyses. Prognostic performance of Aβ-PET and survival analyses with different risk factors (gender, Aβ-PET and APOE ε4 allele status) were also performed. U-p53AZ differentiated neuropsychologically graded AD from non-AD samples, and its detection at intermediate/high levels precisely identified present and future symptomatic AD. In both time-independent and time-dependent prognostic analyses U-p53AZ achieved area under the curve (AUC) \u3e98%, significantly higher than Aβ-PET AUCs (between 84% and 93%, P respectively \u3c0.0001 and \u3c0.001). As single factor, U-p53AZ could clearly determine the risk of AD neuropsychological diagnosis over time (low versus intermediate/high U-p53AZ hazard ratio=2.99). Proportional hazards regression analysis identified U-p53AZ levels as a major independent predictor of AD onset. CONCLUSIONS: These findings support use of U-p53AZ as blood-based biomarker predicting whether individuals would reach neuropsychologically-defined AD within six years prior to AD diagnosis. Integration of U-p53AZ in screening processes could support refined participant stratification for interventional studies

The effect of bull bars on head impact kinematics in pedestrian crashes

This study sought to assess the effect of bull bars on the head kinematics and head impact severity of an adult pedestrian in a collision. Multibody models were created to represent a range of sport-utility vehicles and common bull bar geometries and materials. The contact-impact behaviours of the pedestrian-vehicle interactions were determined from a series of impact tests with the vehicles and the bull bars being modelled. A generalised Hunt-Crossley damping model was fitted to the test data. The interaction models were implemented in MADYMO models of a vehicle pedestrian collision using the geometry of the vehicles and bull bars and a fiftieth percentile male human model. Head kinematics were extracted and the head impact severity estimated. The speed of the head impact with the bonnet was increased by between 7 and 55 percent in simulations where a bull bar was fitted to the vehicle. The increase in head impact velocity was not related to the bull bar material type. The 55 percent increase in head impact speed produced a 249 percent increase in HIC value, using a head-bonnet interaction model based on Australasian NCAP head impact test results. The location of the head impact was affected by the bull bar but the effect was not consistent. The simulation results show that the addition of a bull bar to the front of a vehicle increases the speed of the head impact with the bonnet. This speed increase appears to be less a product of the material the bull bar is made from, but more a product of the geometry of the bull bar. This suggests that bull bar geometries could be altered to improve pedestrian collision kinematics possibly even lessening the severity of the head impact with the bonnet. Combined with a soft material, such as polymer, this may lead to a safer bull bar designs for pedestrians.RWG Anderson, S Doecke, AL van den Berg, DJ Searson, G Pont

Application of the NIA-AA research framework: Towards a biological definition of Alzheimer’s disease using cerebrospinal fluid biomarkers in the AIBL study

BACKGROUND: The National Institute on Aging and Alzheimer’s Association (NIA-AA) have proposed a new Research Framework: Towards a biological definition of Alzheimer’s disease, which uses a three-biomarker construct: Aß-amyloid, tau and neurodegeneration AT(N), to generate a biomarker based definition of Alzheimer’s disease. OBJECTIVES: To stratify AIBL participants using the new NIA-AA Research Framework using cerebrospinal fluid (CSF) biomarkers. To evaluate the clinical and cognitive profiles of the different groups resultant from the AT(N) stratification. To compare the findings to those that result from stratification using two-biomarker construct criteria (AT and/or A(N)). DESIGN: Individuals were classified as being positive or negative for each of the A, T, and (N) categories and then assigned to the appropriate AT(N) combinatorial group: A-T-(N)-; A+T-(N)-; A+T+(N)-; A+T-(N)+; A+T+(N)+; A-T+(N)-; A-T-(N)+; A-T+(N)+. In line with the NIA-AA research framework, these eight AT(N) groups were then collapsed into four main groups of interest (normal AD biomarkers, AD pathologic change, AD and non-AD pathologic change) and the respective clinical and cognitive trajectories over 4.5 years for each group were assessed. In two sensitivity analyses the methods were replicated after assigning individuals to four groups based on being positive or negative for AT biomarkers as well as A(N) biomarkers. SETTING: Two study centers in Melbourne (Victoria) and Perth (Western Australia), Australia recruited MCI individuals and individuals with AD from primary care physicians or tertiary memory disorder clinics. Cognitively healthy, elderly NCs were recruited through advertisement or via spouses of participants in the study. PARTICIPANTS: One-hundred and forty NC, 33 MCI participants, and 27 participants with AD from the AIBL study who had undergone CSF evaluation using Elecsys® assays. INTERVENTION (if any): Not applicable. MEASUREMENTS: Three CSF biomarkers, namely amyloid β1-42, phosphorylated tau181, and total tau, were measured to provide the AT(N) classifications. Clinical and cognitive trajectories were evaluated using the AIBL Preclinical Alzheimer Cognitive Composite (AIBL-PACC), a verbal episodic memory composite, an executive function composite, California Verbal Learning Test – Second Edition; Long-Delay Free Recall, Mini-Mental State Examination, and Clinical Dementia Rating Sum of Boxes scores. RESULTS: Thirty-eight percent of the elderly NCs had no evidence of abnormal AD biomarkers, whereas 33% had biomarker levels consistent with AD or AD pathologic change, and 29% had evidence of non-AD biomarker change. Among NC participants, those with biomarker evidence of AD pathology tended to perform worse on cognitive outcome assessments than other biomarker groups. Approximately three in four participants with MCI or AD had biomarker levels consistent with the research framework’s definition of AD or AD pathologic change. For MCI participants, a decrease in AIBL-PACC scores was observed with increasing abnormal biomarkers; and increased abnormal biomarkers were also associated with increased rates of decline across some cognitive measures. CONCLUSIONS: Increasing biomarker abnormality appears to be associated with worse cognitive trajectories. The implementation of biomarker classifications could help better characterize prognosis in clinical practice and identify those at-risk individuals more likely to clinically progress, for their inclusion in future therapeutic trials

Plasma high‐density lipoprotein cargo is altered in Alzheimer's disease and is associated with regional brain volume

Cholesterol levels have been repeatedly linked to Alzheimer's Disease (AD), suggesting that high levels could be detrimental, but this effect is likely attributed to Low-Density Lipoprotein (LDL) cholesterol. On the other hand, High-Density Lipoproteins (HDL) cholesterol levels have been associated with reduced brain amyloidosis and improved cognitive function. However, recent findings have suggested that HDL-functionality, which depends upon the HDL-cargo proteins associated with HDL, rather than HDL levels, appears to be the key factor, suggesting a quality over quantity status. In this report, we have assessed the HDL-cargo (Cholesterol, ApoA-I, ApoA-II, ApoC-I, ApoC-III, ApoD, ApoE, ApoH, ApoJ, CRP, and SAA) in stable healthy control (HC), healthy controls who will convert to MCI/AD (HC-Conv) and AD patients (AD). Compared to HC we observed an increased cholesterol/ApoA-I ratio in AD and HC-Conv, as well as an increased ApoD/ApoA-I ratio and a decreased ApoA-II/ApoA-I ratio in AD. Higher cholesterol/ApoA-I ratio was also associated with lower cortical grey matter volume and higher ventricular volume, while higher ApoA-II/ApoA-I and ApoJ/ApoA-I ratios were associated with greater cortical grey matter volume (and for ApoA-II also with greater hippocampal volume) and smaller ventricular volume. Additionally, in a clinical status-independent manner, the ApoE/ApoA-I ratio was significantly lower in APOE ε4 carriers and lowest in APOE ε4 homozygous. Together, these data indicate that in AD patients the composition of HDL is altered, which may affect HDL functionality, and such changes are associated with altered regional brain volumetric data