Differences in state drug testing and reporting by driver type in U.S. fatal traffic crashes

IntroductionDriving under the influence of drugs, including marijuana, has become more prevalent in recent years despite local, state, and federal efforts to prevent such increases. The Fatality Analysis Reporting System (FARS) is the primary source of drugged driving data for fatal crashes in the United States but lacks the completeness required to calculate unbiased estimates of drug use among drivers involved in fatal crashes.MethodsThis article uses the 2013 FARS dataset to present differences in state drug testing rates by driver type, driver fault type, and state-level factors; discusses limitations related to analysis and interpretation of drugged driving data; and offers suggestions for improvements that may enable appropriate use of FARS drug testing data in the future.ResultsResults showed that state drug testing rates were highest among drivers who died at the scene of the crash (median = 70.8%) and drivers who died and were at fault in the crash (median = 64.4%). The lowest testing rates were seen among surviving drivers who were not transported to a hospital (median = 14.0%) and surviving drivers who were not at fault in the crash (median = 10.0%). Drug testing rates differed by state blood alcohol content (BAC) testing rate across all driver types and driver fault types, and in general, states that tested a higher percentage of drivers for BAC had higher drug testing rates.DiscussionTesting rates might be increased through standardization and mandatory testing policies. FARS data users should continue to be cautious about the limitations of using currently available data to quantify drugged driving. More efforts are needed to improve drug testing and reporting practices, and more research is warranted to establish drug concentration levels at which driving skills become impaired.     

Alcohol and driving factors in collision risk

In this study we examine the effect of several alcohol-related measures on self-reported collision involvement within the previous 12 months while controlling for demographic and driving exposure factors based on a large representative sample of adults in Ontario. Data are based on the 2002–2006 Centre for Addiction and Mental Health Monitor, an ongoing cross-sectional telephone survey of Ontario adults aged 18 and older (n = 8542). Three logistic regressions of self-reported collision involvement in the past 12 months were implemented, each consisting of 3 steps: (1) demographic factors and driving exposure entered, (2) driving after drinking within the last 12 months entered, and (3) one of three alcohol-related measures (AUDIT subscales of alcohol consumption, dependence and problems) entered. In each step, measures from the preceding step were included in order to control for those variables. In Step 1, age (OR = 0.989), region overall, Central East region (OR = 0.71), West region (OR = 0.67), and North region (OR = 0.67), income overall and those who did not state income (OR = 0.64), marital status overall and those married or living common law (OR = 0.60), and number of kilometers driven in a typical week (OR = 1.00) were found to be significant predictors of collision involvement. The analyses revealed that driving after drinking was a significant predictor of collision involvement in Step 2 (OR = 1.51) and each of the Step 3 models (ORs = 1.52, 1.37, 1.34). The AUDIT Consumption subscale was not a significant factor in collision risk. Both the AUDIT Dependence and AUDIT Problems subscales were significantly related to collision risk (ORs = 1.13 and 1.10, respectively). These findings suggest that alcohol, in addition to its effects on collision risk through its acute impairment of driving skills, may also affect collision risk through processes involved when individuals develop alcohol problems or alcohol dependence.     

A video based run-off-road training program with practice and evaluation in a simulator

A run-off-road (ROR) event occurs when one or more of a vehicle’s wheels leaves the roadway and begins to travel on the surface or shoulder adjacent to the road. Despite various countermeasures, ROR crashes continue to yield a large number of fatalities and injuries. Infrastructure-based solutions do not directly address the critical factor of driver performance preceding and during an ROR event. In this study, a total of 75 individuals participated in a pre–post experiment to examine the effect of a training video on improving driver performance during a set of simulated ROR scenarios (e.g., on a high speed highway, a horizontal curve, and a residential rural road). In each scenario, the vehicle was unexpectedly forced into an ROR scenario for which the drivers were instructed to recover as safely as possible. The treatment group then watched a custom ROR training video while the control group viewed a placebo video. The participants then drove the same simulated ROR scenarios. The results suggest that the training video had a significant positive effect on drivers’ steering response on all three roadway conditions as well as improvements in vehicle stability, subjectively rated demand on the driver, and self-evaluated performance in the highway scenario. Under the highway conditions, the treatment group reduced the frequency of spinouts from 70% in the pre-training events to 16% in the post-training events (χ²(1) = 23.32, p < 0.001) with no significant improvement found for the control group. In the horizontal curve, spinouts were reduced for the treatment group from 50% in the pre-training events to 30% in the post-training events (χ²(1) = 8.45, p = 0.004) with the control group also not showing any significant improvement. The results of this study suggest that even a short video about recovering from ROR events can significantly influence a driver’s ability to recover. It is possible that additional training may have further benefits in recovering from ROR events.     

Pedestrian injury risk and the effect of age

Older adults and pedestrians both represent especially vulnerable groups in traffic. In the literature, hazards are usually described by the corresponding injury risks of a collision. This paper investigates the MAIS3 + F risk (the risk of sustaining at least one injury of AIS 3 severity or higher, or fatal injury) for pedestrians in full-frontal pedestrian-to-passenger car collisions.Using some assumptions, a model-based approach to injury risk, allowing for the specification of individual injury risk parameters for individuals, is presented. To balance model accuracy and sample size, the GIDAS (German In-depth Accident Study) data set is divided into three age groups; children (0–14); adults (15–60); and older adults (older than 60). For each group, individual risk curves are computed. Afterwards, the curves are re-aggregated to the overall risk function.The derived model addresses the influence of age on the outcome of pedestrian-to-car accidents. The results show that older people compared with younger people have a higher MAIS3 + F injury risk at all collision speeds. The injury risk for children behaves surprisingly. Compared to other age groups, their MAIS3 + F injury risk is lower at lower collision speeds, but substantially higher once a threshold has been exceeded. The resulting injury risk curve obtained by re-aggregation looks surprisingly similar to the frequently used logistic regression function computed for the overall injury risk. However, for homogenous subgroups – such as the three age groups – logistic regression describes the typical risk behavior less accurately than the introduced model-based approach.Since the effect of demographic change on traffic safety is greater nowadays, there is a need to incorporate age into established models. Thus far, this is one of the first studies incorporating traffic participant age to an explicit risk function. The presented approach can be especially useful for the modeling and prediction of risks, and for the evaluation of advanced driver assistance systems.     

Effect of exposure to aggressive stimuli on aggressive driving behavior at pedestrian crossings at unmarked roadways

BackgroundAggressive driving, influenced by the proneness of driving aggression, angry state and provoking situation, is adversely affecting traffic safety especially in developing countries where pedestrians frequently cross an unmarked crosswalk. Exposure to aggressive stimuli causes driving anger and aggressive driving behaviors, but the exposure effect on higher and lower aggression drivers and their cumulative changes under successive exposures need more investigation.ObjectivesAn experiment was conducted to examine (1) driving behaviors of individuals with higher and lower aggressive driving traits when approaching pedestrian crossings at unmarked roadways with and without aggressive provocation; and (2) cumulative changes of driving performance under repeated provocations.MethodWe conducted a driving simulator study with 50 participants. Trait of aggressive driving served as a between-subjects variable: participants with an Aggressive Driving Scale (ADS) total score of 30 or more (for men) or 23 or more (for women) were regarded as higher aggressive drivers; lower aggressive drivers were those individuals whose ADS total scores were 21 or less (for men) or 13 or less (for women). Exposure to aggressive stimuli (provoked vs. non-provoked condition) served as a within-subjects variable. Several aspects of the participants’ minimum driving speed, lateral distance from a simulated pedestrian, lateral deviation, and subjective measures were collected.ResultsWe found that drivers with higher aggressive driving traits were more likely to feel irritated and fail to give way for pedestrians and drove closer to pedestrians when exposed to sustained honking and improper passing compared to the non-provoked condition. This trait × state interaction only occurred when pedestrians crossed the street from the right roadway edge line. In addition, we observed an accumulation effect of exposure to aggressive stimuli on driver's aggressive behaviors at pedestrian crossings.ConclusionsEnvironmental design, law enforcement, and educational campaign may have practical value for reducing pedestrian and driver conflicts at unmarked roadways.     

Investigating risky,distracting, and protective peer passenger effects in a dual process framework

Prior studies indicated higher collision rates among young novice drivers with peer passengers. This driving simulator study provided a test for a dual process theory of risky driving by examining social rewards (peer passengers) and cognitive control (inhibitory control). The analyses included age (17–18 yrs, n = 30; 21–24 yrs, n = 20). Risky, distracting, and protective effects were classified by underlying driver error mechanisms. In the first drive, participants drove alone. In the second, participants drove with a peer passenger. Red-light running (violation) was more prevalent in the presence of peer passengers, which provided initial support for a dual process theory of risk driving. In a subgroup with low inhibitory control, speeding (violation) was more prevalent in the presence of peer passengers. Reduced lane-keeping variability reflected distracting effects. Nevertheless, possible protective effects for amber-light running and hazard handling (cognition and decision-making) were found in the drive with peer passengers. Avenues for further research and possible implications for targets of future driver training programs are discussed.     

Driving with pets and motor vehicle collision involvement among older drivers: A prospective population-based study

ObjectiveDistracted driving is a major cause of motor vehicle collision (MVC) involvement. Pets have been identified as potential distraction to drivers, particularly in the front. This type of distraction could be worse for those with impairment in the cognitive aspects of visual processing. The purpose of this study is to evaluate the association between driving with pets and rates of motor vehicle collision involvement in a cohort of older drivers.MethodsA three-year prospective study was conducted in a population-based sample of 2000 licensed drivers aged 70 years and older. At the baseline visit, a trained interviewer asked participants about pet ownership, whether they drive with pets, how frequently, and where the pet sits in the vehicle. Motor vehicle collision (MVC) involvement during the three-year study period was obtained from the Alabama Department of Public Safety. At-fault status was determined by the police officer who arrived on the scene. Participants were followed until the earliest of death, driving cessation, or end of the study period. Poisson regression was used to calculate crude and adjusted rate ratios (RR) examining the association between pet ownership, presence of a pet in a vehicle, frequency of driving with a pet, and location of the pet inside with vehicle with any and at-fault MVC involvement. We examined whether the associations differed by higher order visual processing impairment status, as measured by Useful Field of View, Trails B, and Motor-free Visual Perception Test.ResultsRates of crash involvement were similar for older adults who have ever driven with a pet compared to those who never drove with their pet (RR = 1.15, 95% CI 0.76–1.75). Drivers who reported always or sometimes driving with their pet had higher MVC rates compared to pet owners who never drive with a pet, but this association was not statistically significant (RR = 1.39, 95% CI 0.86–2.24). In terms of location, those reporting having a pet frequently ride in the front of the vehicle had similar rates of MVC involvement compared to those who did not drive with a pet in the front. A similar pattern of results was observed for at-fault MVCs. This association was not modified by visual processing impairment status.ConclusionThe current study demonstrates a positive but non-significant association between frequently driving with pets and MVC involvement. More research is needed, particularly on restraint use and whether the pet was in the car at the time of the crash, to help characterize the public safety benefit of regulations on driving with pets.     

Severity of disability related to road traffic crashes in the Spanish adult population

BackgroundThe severity of disability related to road traffic crashes has been little studied, despite the significant health and socio-economic impacts that determine victims’ quality of life.ObjectiveTo estimate the consequences of road traffic crashes on the severity of disability, in terms of individuals’ capacity to execute activities and perform tasks in their current environment, using aids.MethodsCross-sectional study conducted on community-dwelling participants in the “2008 National Survey of Disability”, with data on 91,846 households having 20,425 disabled persons, 443 of whom had disability due to road traffic crashes. We measured severity using two indicators, i.e., the Capacity (CSI) and Performance (PSI) Severity Indices.ResultsThe highest proportion of disability was mild (CSI = 70.5%; PSI = 80.8%), while 7.6% (CSI) and 4.9% (PSI) was severe/complete respectively. The moderate/severe disability rate was 0.6 per thousand on the CSI, decreasing to 0.4 per thousand on the PSI. No differences were observed by age or sex. Moderate/severely disabled persons had a fourfold higher probability of being retired or unfit for work. Mental and nervous system impairments were more closely related to moderate/severe/complete problems of capacity and performance (p < 0.001), disability for carrying out general tasks and demands, and interpersonal interactions and relationships (p < 0.001). Being permanently bedridden (p < 0.001), receiving aids (p < 0.001), family support (p < 0.05) and moving home (p < 0.05) increased with an increase in the level of severity.ConclusionRoad traffic crashes mainly cause mild disability. Moderate/severe disability is associated with lower work capacity, greater functional dependence, and increased need of aids, moving home and family support.     

Crash avoidance in response to challenging driving events: The roles of age,serialization, and driving simulator platform

We examined the crash avoidance behaviors of older and middle-aged drivers in reaction to six simulated challenging road events using two different driving simulator platforms. Thirty-five healthy adults aged 21–36 years old (M = 28.9 ± 3.96) and 35 healthy adults aged 65–83 years old (M = 72.1 ± 4.34) were tested using a mid-level simulator, and 27 adults aged 21–38 years old (M = 28.6 ± 6.63) and 27 healthy adults aged 65–83 years old (M = 72.7 ± 5.39) were tested on a low-cost desktop simulator. Participants completed a set of six challenging events varying in terms of the maneuvers required, avoiding space given, directional avoidance cues, and time pressure. Results indicated that older drivers showed higher crash risk when events required multiple synchronized reactions. In situations that required simultaneous use of steering and braking, older adults tended to crash significantly more frequently. As for middle-aged drivers, their crashes were attributable to faster driving speed. The same age-related driving patterns were observed across simulator platforms. Our findings support the hypothesis that older adults tend to react serially while engaging in cognitively challenging road maneuvers.     

The role of parental alcohol consumption on driving under the influence of alcohol: Results from a longitudinal,nationally representative sample

PurposeMany studies have examined the role of peer and parental alcohol use on drinking behaviors among adolescents. Few studies, however, have examined parental influences on driving under the influence (DUI) of alcohol. The current study uses data from a longitudinal study to examine the role of parental alcohol use during adolescence on the risk for DUI among young adult men and women.MethodsData were derived from 9559 adolescents and young adults who participated in the National Longitudinal Study of Adolescent Health (Add Health) Waves I and III. Survey logistic regression was used to examine the relationship between multilevel risk and protective factors and self-reported DUI. Analyses were stratified by gender and frequency of parental alcohol consumption to understand the role of parental alcohol use on risk for DUI among their youth.ResultsRisk and protective factors for DUI were very similar among men and women. Parental alcohol use significantly predicted DUI among women (OR = 1.39, p < 0.01) and men (OR = 1.33, p < 0.05). When parents did not report alcohol use, peer alcohol use significantly increased risk for DUI for both women (OR = 1.26, p < 0.05) and men (OR = 1.31, p < 0.001). When parents reported alcohol use, however, peer alcohol use was not a significant independent predictor.ConclusionsFindings suggest remarkable similarities in risk and protective factors for DUI across gender groups. For men and women, parental alcohol consumption was a risk factor for DUI. Peers’ alcohol use predicted DUI only when parents did not use alcohol.     

Solute cluster size effect on the fatigue crack propagation resistance of an underaged Al–Cu–Mg alloy

The effect of Cu–Mg cluster size and number density on the fatigue fracture behavior of Al–Cu–Mg alloy with various aging conditions was investigated by means of transmission electron microscopy (TEM), atom probe tomography (APT), scanning electron microscopy (SEM) and fatigue testing. Results showed that the fatigue crack propagation (FCP) resistances of 170 °C/1 h and 170 °C/8 h samples were higher than that of 170 °C/0.5 h sample due to increased number density of great size Cu–Mg co-clusters (>50 atoms). These large clusters were harder to dissolve during cycle deformation, thus reduced the cyclic softening effect and enhanced the FCP resistance. Moreover, as aging prolonged, the critical shear stress (τ_m) of co-clusters by modulus hardening increased from 10.2 (MPa) in 170 °C/0.5 h sample to 12.4 in 170 °C/1 h sample and 12.1 in 170 °C/8 h sample. Thus the force required for the movement of dislocations impeded by co-clusters, as well as the resistance of FCP caused by co-clusters, in 170 °C/1 h and 170 °C/8 h sample was higher than that in 170 °C/0.5 h sample. The 170 °C/8 h sample possessed the lower FCP resistance than 170 °C/1 h sample because of the existence of S′ phase. S′ phase was a kind of semi-coherent unshearable precipitate and hence reduced the planar-reversible slip.     

Shrinkage properties of a modified dental resin composites containing a novel spiro-orthocarbonate expanding monomer

ObjectivesThis study investigated the photopolymerization-induced shrinkage properties of conventional methacrylate-based composites modified by a novel spiro-orthocarbonate (SOC) expanding monomer.MethodsThe epoxy monomer and SOC expanding monomer were added to a methacrylate-based resin matrix at five different ratios ranging from 20 wt.% (SOC + Epoxy) (group 1) to 60 wt.% (SOC + Epoxy) (group 5). Volumetric shrinkage and contraction stress developing after polymerization were measured using X-ray micro-computed tomography and a universal testing machine, respectively.ResultsThe volumetric shrinkage of the resin composite samples ranged from 0.92% (group 5) to 3.85% (control group) 30 min after light curing. Group 5 had the lowest volumetric shrinkage (p < 0.05), followed by groups 4, 3, 2 and 1. The contraction stress of the materials ranged from 1.86 MPa (group 5) to 3.56 MPa (control group). The lowest contraction stress was also observed in group 5, 30 min after curing (p < 0.05).ConclusionIncluding SOC expanding monomer reduced volumetric shrinkage and contraction stress of composites in comparison with conventional methacrylate-based composites.     

Quantifying the yellow signal driver behavior based on naturalistic data from digital enforcement cameras

The yellow signal driver behavior, reflecting the dilemma zone behavior, is analyzed using naturalistic data from digital enforcement cameras. The key variable in the analysis is the entrance time after the yellow onset, and its distribution. This distribution can assist in determining two critical outcomes: the safety outcome related to red-light-running angle accidents, and the efficiency outcome. The connection to other approaches for evaluating the yellow signal driver behavior is also discussed.The dataset was obtained from 37 digital enforcement cameras at non-urban signalized intersections in Israel, over a period of nearly two years. The data contain more than 200 million vehicle entrances, of which 2.3% (∼5 million vehicles) entered the intersection during the yellow phase. In all non-urban signalized intersections in Israel the green phase ends with 3 s of flashing green, followed by 3 s of yellow. In most non-urban signalized roads in Israel the posted speed limit is 90 km/h.Our analysis focuses on crossings during the yellow phase and the first 1.5 s of the red phase. The analysis method consists of two stages. In the first stage we tested whether the frequency of crossings is constant at the beginning of the yellow phase. We found that the pattern was stable (i.e., the frequencies were constant) at 18 intersections, nearly stable at 13 intersections and unstable at 6 intersections. In addition to the 6 intersections with unstable patterns, two other outlying intersections were excluded from subsequent analysis. Logistic regression models were fitted for each of the remaining 29 intersection. We examined both standard (exponential) logistic regression and four parameters logistic regression. The results show a clear advantage for the former. The estimated parameters show that the time when the frequency of crossing reduces to half ranges from1.7 to 2.3 s after yellow onset. The duration of the reduction of the relative frequency from 0.9 to 0.1 ranged from 1.9 to 2.9 s.     

Influences of magnetic annealing on the grain growth in a cryoECAPed 1050 aluminum alloy

The evolutions of hardness, grain microstructures and dislocations were investigated in cryoECAPed 1050 aluminum alloy after annealing at 423–673 K for 1 h without and with a magnetic field of 12 T. Compared to those of samples annealed without the magnetic field, the hardness of samples annealed with the magnetic field is lower at 423–573 K, and then higher at > 573 K. The high magnetic field accelerates the formation of dislocation cells or sub-grains. The interface dislocations frequently observed in materials deformed at high temperature were detected in samples annealed with the magnetic field at ≥ 423 K. The fraction of low angle boundaries in sample annealed with the field is 49% and 34% in sample annealed without the field even at 673 K. No abnormal grain growth occurs in samples annealed with the magnetic field due to the rapid consumption of the stored distortion energy during recovery.     

Investigation of the electromagnetic characteristics of cement based composites filled with EPS

Due to the electromagnetic transparency of expanded polystyrene (EPS), the cement-based composites filled with EPS beads can be regarded as a type of “porous” material. The electromagnetic reflection loss of this porous composite material in the frequency range from 8 to 18 GHz was studied experimentally in this paper. Findings show that the filling of EPS beads can improve the reflection loss of plain cement material greatly and the EPS filling ratio, EPS bead size and sample thickness all have remarkable effects on the electromagnetic wave reflection loss of this porous composite material. With a EPS filling volume concentration of 60% and EPS size of 1 mm, the reflection loss is all higher than −8 dB in 8–18 GHz and the bandwidth for −10 dB reaches 6.2 GHz for a sample with the thickness of 20 mm. This composite material still has a relatively low bulk density and can be handled easily.     

Photoluminescence and thermoluminescence studies of Tb3+ doped ZnO nanorods

Here in, the synthesis of the terbium doped zinc oxide (ZnO:Tb³⁺) nanorods via room temperature chemical co-precipitation was explored and their structural, photoluminescence (PL) and thermoluminescence (TL) studies were investigated in detail. The present samples were found to have pure hexagonal wurtzite crystal structure. The as obtained samples were broadly composed of nanoflakes while the highly crystalline nanorods have been formed due to low temperature annealing of the as synthesized samples. The diameters of the nanoflakes are found to be in the range 50–60 nm whereas the nanorods have diameter 60–90 nm and length 700–900 nm. FTIR study shows ZnO stretching band at 475 cm^?1 showing improved crystal quality with annealing. The bands at 1545 and 1431 cm^?1 are attributed to asymmetric and symmetric CO stretching vibration modes. The diffuse reflectance spectra show band edge emission near 390 nm and a blue shift of the absorption edge with higher concentration of Tb doping. The PL spectra of the Tb³⁺-doped sample exhibited bright bluish green and green emissions at 490 nm (⁵D₄ → ⁷F₆) and 544 nm (⁵D₄ → ⁷F₅) respectively which is much more intense then the blue (450 nm), bluish green (472 nm) and broad green emission (532 nm) for the undoped sample. An efficient energy transfer process from ZnO host to Tb³⁺ is observed in PL emission and excitation spectra of Tb³⁺-doped ZnO ions. The doped sample exhibits a strong TL glow peak at 255 °C compared to the prominent glow peak at 190 °C for the undoped sample. The higher temperature peaks are found to obey first order kinetics whereas the lower temperature peaks obey 2nd order kinetics. The glow peak at 255 °C for the Tb³⁺ doped sample has an activation energy 0.98 eV and frequency factor 2.77 × 10⁸ s^?1.     

Risk appraisal of passing zones on two-lane rural highways and policy applications

Passing on two-lane rural highways is associated with risks of head-on collision resulting from unsafe completion of passing maneuvers in the opposite traffic lane. In this paper, we explore the use of time-to-collision (TTC) as a surrogate safety measure of the risk associated with passing maneuvers. Logistic regression models to predict the probability to end the passing maneuver with TTC less than 2 or 3 s-threshold were developed with the time-gap from initiation of the maneuver to arrival of the opposite vehicle (effective accepted gap), and the passing duration as explanatory variables. The data used for model estimation was collected using stationary tripod-mounted camcorders at 19 passing zones in Uganda. Results showed that passing maneuvers completed with TTC less than 3 s are unsafe and often involved sudden speed reduction, flashing headlights, and lateral shift to shoulders. Model sensitivity analysis was conducted for observed passing durations involving passenger cars or short trucks (2–3 axles), and long trucks (4–7 axles) as the passed vehicles for 3 s TTC-threshold. Three risk levels were proposed based on the probability to complete passing maneuvers with TTC less than 3 s for a range of opposite direction traffic volumes. Applications of the results for safety improvements of two-lane rural highways are also discussed.     

Long-term effect of the North Carolina graduated driver licensing system on licensed driver crash incidence: A 5-year survival analysis

Several studies document the success of graduated driver licensing (GDL) systems in reducing young teen crash rates, but it is not yet clear whether any portion of the crash reduction is achieved by producing more capable drivers. The purpose of this study was to determine whether young teen drivers licensed under the North Carolina GDL system remain crash-free longer than those licensed prior to GDL, independent of the crude reductions in exposure (i.e., decreasing and delaying licensure) that may be responsible for most documented effects of GDL. Survival analysis was used to compare retrospective cohorts of 16–17 year olds before (n = 105,569) and after (n = 327,054) the North Carolina GDL system was implemented. The crash incidence of GDL-licensed 16–17 year olds (combined) was 10% lower than that for pre-GDL teens for at least 5 years after being licensed to drive independently (hazard ratio [HR] = 0.90; 95% confidence interval [CI] = 0.89, 0.91). However, more refined analysis revealed the reductions to only be among females (7%; HR = 0.93; CI = 0.91, 0.94) and males (15%; HR = 0.85, CI = 0.84, 0.87) licensed at age 16 and not among females (0%; HR = 1.00; CI = 0.95, 1.06) and males (0%; HR = 1.00; CI = 0.92, 1.09) licensed at age 17. Sixteen-year-old drivers licensed under the North Carolina GDL system experienced lower first-crash incidence during the first 5 years of unsupervised driving than did those licensed under the previous system. The benefits are greater for males, who tend to have higher crash rates. The findings contradict conventional wisdom that the entire benefit of GDL results merely from decreasing or delaying licensure among young drivers.     

Motorcycle protective clothing: Protection from injury or just the weather?

BackgroundApart from helmets, little is known about the effectiveness of motorcycle protective clothing in reducing injuries in crashes. The study aimed to quantify the association between usage of motorcycle clothing and injury in crashes.Methods and findingsCross-sectional analytic study. Crashed motorcyclists (n = 212, 71% of identified eligible cases) were recruited through hospitals and motorcycle repair services. Data was obtained through structured face-to-face interviews. The main outcome was hospitalization and motorcycle crash-related injury. Poisson regression was used to estimate relative risk (RR) and 95% confidence intervals for injury adjusting for potential confounders.ResultsMotorcyclists were significantly less likely to be admitted to hospital if they crashed wearing motorcycle jackets (RR = 0.79, 95% CI: 0.69–0.91), pants (RR = 0.49, 95% CI: 0.25–0.94), or gloves (RR = 0.41, 95% CI: 0.26–0.66). When garments included fitted body armour there was a significantly reduced risk of injury to the upper body (RR = 0.77, 95% CI: 0.66–0.89), hands and wrists (RR = 0.55, 95% CI: 0.38–0.81), legs (RR = 0.60, 95% CI: 0.40–0.90), feet and ankles (RR = 0.54, 95% CI: 0.35–0.83). Non-motorcycle boots were also associated with a reduced risk of injury compared to shoes or joggers (RR = 0.46, 95% CI: 0.28–0.75). No association between use of body armour and risk of fracture injuries was detected. A substantial proportion of motorcycle designed gloves (25.7%), jackets (29.7%) and pants (28.1%) were assessed to have failed due to material damage in the crash.ConclusionsMotorcycle protective clothing is associated with reduced risk and severity of crash related injury and hospitalization, particularly when fitted with body armour. The proportion of clothing items that failed under crash conditions indicates a need for improved quality control. While mandating usage of protective clothing is not recommended, consideration could be given to providing incentives for usage of protective clothing, such as tax exemptions for safety gear, health insurance premium reductions and rebates.     

Effects of warm rolling and ageing after cryogenic rolling on mechanical properties and microstructure of Al 6061 alloy

The mechanical properties and microstructural evolution of Al 6061 alloy subjected to cryorolling and warm rolling have been investigated in the present work. The Al 6061 alloy was subjected to thickness reduction of 70% by cryorolling followed by thickness reduction of 20% by warm rolling. The cryorolled + warmrolled (CR + WR) samples were characterized by Electron back scattered diffraction (EBSD) technique, Differential scanning calorimetry (DSC), X-Ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) technique to substantiate the role of deformation strain and temperature on their microstructural features and compared with cryorolled (CR) samples. The CR + WR samples showed a significant improvement in tensile strength (376 MPa) and partial improvement in ductility (5%) as measured from tensile testing. It is mainly due to the combined effect of partial grain refinement, solid solution strengthening, dislocation hardening, dynamic recovery, and dynamic ageing during cryorolling and warm rolling. The effect of ageing on CR + WR samples was investigated and the optimum ageing condition was found to be 45 h at 125 °C, which gives improved tensile strength of (406 MPa) and good tensile ductility (10%). The tensile strength of cryorolled + warm rolled + peak aged (CR + WR + PA) sample (406 MPa) was found to be 11.2% more than that of cryorolled + peak aged (CR + PA) sample (365 MPa). During peak ageing treatment, the strength has been retained by pinning of dislocations through nanosized precipitates generated during warm rolling and it has been improved further by precipitation of the remnant dissolved second phase in the matrix. However, the observed ductility of CR + PA sample was 13% more than CR + WR + PA sample due to low dislocation density after ageing.