An experimental evaluation of the effects of periodic motor vehicle inspection on accident rates

204,000 cars were randomly assigned to three different experimental conditions. 46,000 cars were inspected annually during a period of three years; 46,000 cars were inspected once during three years; and 112,000 cars were not inspected. The number of accidents was recorded for a period of four years. No differences in accident rates were found between the groups. The technical condition of inspected vehicles improved compared to those not inspected. The experiment did not have any unintended side-effects. It is concluded that periodic motor vehicle inspection has no preventive effect on the technical condition of cars in a system where roadside inspections also exist.     

Further research on accident rates in developing countries

Earlier studies have shown that by using cross-sectional data for a group of developing countries, a significant relationship can be established between fatality rates and vehicle ownership levels. This paper updates relationships established in earlier years and identifies whether or not the slope of the regression line has continued to increase (and suggests that for the group of countries as a whole, there is a worsening in the safety situation). Similar relationships are also established for casualty rates. A detailed analysis is made of the relationship between fatality rates and parameters which describe, in part, the social, physical and economic characteristics of the developing countries. These include vehicle ownership, gross national product per capita, road density, vehicle density (per kilometre of road), population per physician and population per hospital bed. Again, comparisons are made with results obtained on earlier studies.     

Tobit analysis of vehicle accident rates on interstate highways

There has been an abundance of research that has used Poisson models and its variants (negative binomial and zero-inflated models) to improve our understanding of the factors that affect accident frequencies on roadway segments. This study explores the application of an alternate method, tobit regression, by viewing vehicle accident rates directly (instead of frequencies) as a continuous variable that is left-censored at zero. Using data from vehicle accidents on Indiana interstates, the estimation results show that many factors relating to pavement condition, roadway geometrics and traffic characteristics significantly affect vehicle accident rates.     

Traffic accident rates among finnish out-patients

A questionnaire was administered to 765 rheumatoid arthritic, 715 tuberculous, and 1050 psychiatric outpatients concerning their use of alcohol and drugs, driving habits, and traffic accident involvement. The same questionnaire was administered to 587 controls. The driving populations of all groups were matched as to their age, and living district. The main finding of the study was that, as the traffic exposure was controlled, the non-drug treated patients were not involved in accidents more often than the controls. In the psychiatric out-patient group, drug use was linked with an increased accident rate. Heavy use of alcohol was linked with increased traffic exposure in the present study. The combined use of alcohol and drugs tended to increase one's involvement in accidents.     

Highway accident rates and rural travel densities

Rural highway injury accident rates should theoretically increase with an increase in travel densities. Regression analyses of cross-sectional data on U.S. Primary and Secondary highways show a moderate positive association, but on the Interstate this association appears to be invariant. Fatal accident rates, on the other hand, are negatively associated with travel densities. Explanations for these results may be found in variables associated with travel densities, such as speed, speed variability, types of crash, and accessibility to emergency medical services. Changes in travel densities, between 1976 and 1979. on the major rural highway systems have been accommodated with no apparent effect on average accident rates.     

The variation of drivers' accident rates between drivers and over time.

Accident records of individual drivers in eight large samples from the general driving population have been analysed as nonhomogeneous Poisson processes, i.e. by assuming that each driver's accidents occur randomly with an individual underlying accident rate that varies in time. Previous hypotheses about the form of this variation are reviewed. The moments of the distribution over drivers of individual underlying accident rates averaged over periods of one or more years are estimated; they indicate that most of the distributions are intermediate in form between the gamma and lognormal distributions. The results suggest the presence of an overall annual factor that multiplies all the individual rates; when this is removed the remaining process is approximately stationary (i.e. the mean and standard deviation are approximately constant in time). The coefficient of variation of individual accident rates falls slowly as the length of the period over which they are averaged increases, indicating positive correlation between the underlying accident rates of the same drivers in different periods. These correlations are estimated directly from the accident frequency data, which appears to be a new and useful method of analysis. For one sample, which spans 14 years, the correlation between two adjacent years is about 0.74 and falls approximately linearly to about 0.49 for two years separated by a gap of 12 years. A "switching process" with differing individual means, previously proposed for drivers' accidents by Bartlett, does not appear to fit these results well. A "scaling process," studied by Mandelbrot and previously found to apply in a number of different fields, provides a better fit to the data and could represent the combined effect of a hierarchy of switching processes operating on different time scales, in accordance with what is known or conjectured about the variation of factors affecting accident rates. Although the data analysed are affected by variation in exposure between drivers, the methods and ideas used have implications that may help to resolve the long-standing dispute about individual accident proneness.     

Analysis of the effect of car size on accident injury probability using automobile insurance data

The Highway Loss Data Institute (HLDI) compiles injury and collision claim information from major insurance companies. These data have indicated that a disproportionately large number of injury claims are made for small cars. As a result, it might be concluded that small cars increase injury risk to their occupants. Recent advertisements by a major automobile manufacturer suggest a similar conclusion should be drawn from these data. In this paper it is shown that the apparent higher injury risk attributed to small cars can reflect the behavior of persons driving small cars. The number of injury claim accidents per collision claim accident is examined as an alternative measure of injury risk. Possible problems in interpretation are discussed.     

Effects of road geometry and traffic volumes on rural roadway accident rates

This paper revisits the question of the relationship between rural road geometric characteristics, accident rates and their prediction, using a rigorous non-parametric statistical methodology known as hierarchical tree-based regression. The goal of this paper is twofold: first, it develops a methodology that quantitatively assesses the effects of various highway geometric characteristics on accident rates and, second, it provides a straightforward, yet fundamentally and mathematically sound way of predicting accident rates on rural roads. The results show that although the importance of isolated variables differs between two-lane and multilane roads, 'geometric design' variables and pavement condition' variables are the two most important factors affecting accident rates. Further, the methodology used in this paper allows for the explicit prediction of accident rates for given highway sections, as soon as the profile of a road section is given.     

降温速率对食品材料冻干特性的影响

用鲜胡萝卜作试验材料,研究了四种降温速率对水分升华率的影响。结果表明,当表层材料通过最大冰晶生长带的时间小于约25min时,材料表层对水蒸气的渗透阻力明显增大,在冻干中表层以下的材料温升较快并出现融化。若在冻干之前刮除表层或降低降温速率,冻干可顺利完成。     

Load interaction effects in propagation lifetime and inspections of railway axles

As well known, an interaction effect arises, on crack propagation, when a specimen or a component is subjected to variable amplitude fatigue loading. Depending on the applied load sequence, a certain amount of retardation or acceleration can then be observed, on the fatigue crack growth rate, with respect to the constant amplitude case. In the case of structural ductile materials, the interaction phenomenon is mainly addressed by the local plasticity at the crack tip and can be explained, from a global point of view, by adopting the crack closure concept. In the present research, load interaction effects in a medium strength steel for railway axles are experimentally analyzed by companion and full-scale specimens. The experimental outcomes show a significant retardation with respect to a simple no-interaction approach and the Strip-Yield model offers good, yet conservative, estimates of crack advance. The consequences of crack growth retardation on the inspection periodicity of railway axles are then discussed.     

The paradox of driving speed: two adverse effects on highway accident rate

Whereas speeding is known to be a substantial risk factor in driving, there is no unequivocal evidence that accident rate on limited-access motor highways is considerably affected by average speed or by speed limits meant to regulate it. It is suggested here that the seeming puzzle actually may have a straightforward explanation: accident-prone interactions (APIs) between cars occur when they pass each other--mostly moving in the same directions or in opposite ones. Such interactions are shown here to happen more frequently, the lower average speed is. To the extent that high speed limits contribute to increase in average speed, they serve to reduce the number of such interactions, thereby to moderate at least part of the negative effect of speed on the driver's ability to avoid an impending accident.     

Fatal accident involvement rates by driver age for large trucks

Survey data on large trucks involved in fatal accidents and on the travel of large trucks provide estimates of fatal accident involvement rates by driver age. The analysis is focused on the implications of lowering the minimum age for drivers of commercial trucks operating interstate from 21 to 19 years. Fatal accident involvement rates for drivers of large trucks are found to increase with decreasing driver age. The younger drivers are over-involved until about age 27. Drivers under the age of 21 are over-involved by a factor of 6 in comparison to the overall rate for all drivers. Other factors known to have significant influences on the probability of involvement in a fatal accident were examined to determine their association with the over-involvement of younger drivers. The general pattern of over-involvement for younger drivers pervades virtually every combination of factors examined. Thus, it is concluded that the basic trend with driver age shown in the aggregate data is primarily associated with age and is not associated with the other factors examined. The results of this analysis substantiate an elevated risk of fatal accident involvement for younger drivers of large trucks.     

Classifications of driving exposure and accident rates for highway safety analysis

Analysis of driving exposure and accident rates will be important in the future for evaluations of highway safety countermeasures. Each should be uniquely classified according to variables of the highway transportation system, i.e. driver-vehicle-road-environment combinations, in order to allow analyses which deal with the most significant differences in exposure and accident rate. Concepts of driving exposure are discussed, and a working definition is presented.     

The effect on accidents of technical inspections of heavy vehicles in Norway

This paper presents a study of the effects on accidents of technical inspections of heavy vehicles (trucks and buses) in Norway. Multiple regression analysis is applied in order to estimate the effects of technical inspections, controlling for annual trend in accident rate, the number of new drivers and annual economic growth. It is found that abolishing inspections may result in an increase of 5–10% in the number of heavy vehicles involved in injury accidents; increasing the number of inspections by 100% is associated with a similar reduction in the number of accidents. These results are not statistically significant and highly uncertain. The study clearly illustrates many of the difficulties often encountered in non-experimental accident research.     

Increased traffic accident rates associated with shale gas drilling in Pennsylvania

Objectives

We examined the association between shale gas drilling and motor vehicle accident rates in Pennsylvania.

Methods

Using publicly available data on all reported vehicle crashes in Pennsylvania, we compared accident rates in counties with and without shale gas drilling, in periods with and without intermittent drilling (using data from 2005 to 2012). Counties with drilling were matched to non-drilling counties with similar population and traffic in the pre-drilling period.

Results

Heavily drilled counties in the north experienced 15–23% higher vehicle crash rates in 2010–2012 and 61–65% higher heavy truck crash rates in 2011–2012 than control counties. We estimated 5–23% increases in crash rates when comparing months with drilling and months without, but did not find significant effects on fatalities and major injury crashes. Heavily drilled counties in the southwest showed 45–47% higher rates of fatal and major injury crashes in 2012 than control counties, but monthly comparisons of drilling activity showed no significant differences associated with drilling.

Conclusions

Vehicle accidents have measurably increased in conjunction with shale gas drilling.     

A study of factors affecting highway accident rates using the random-parameters tobit model

A large body of previous literature has used a variety of count-data modeling techniques to study factors that affect the frequency of highway accidents over some time period on roadway segments of a specified length. An alternative approach to this problem views vehicle accident rates (accidents per mile driven) directly instead of their frequencies. Viewing the problem as continuous data instead of count data creates a problem in that roadway segments that do not have any observed accidents over the identified time period create continuous data that are left-censored at zero. Past research has appropriately applied a tobit regression model to address this censoring problem, but this research has been limited in accounting for unobserved heterogeneity because it has been assumed that the parameter estimates are fixed over roadway-segment observations. Using 9-year data from urban interstates in Indiana, this paper employs a random-parameters tobit regression to account for unobserved heterogeneity in the study of motor-vehicle accident rates. The empirical results show that the random-parameters tobit model outperforms its fixed-parameters counterpart and has the potential to provide a fuller understanding of the factors determining accident rates on specific roadway segments.     

The effects of range versus nonrange driver training on the accident and conviction frequencies of young drivers

The sample consisted of 2,057 high school students from five California high schools who were assigned randomly either to a traditional driver training program (N = 918) or to an experimental program utilizing a driving range (N = 1,139). Aspects of their performance during driver training were measured, as well as performance on tests required for driver licensing and number of days between training and licensing. In addition, Department of Motor Vehicles files supplied information on their accident and conviction records within the year following the beginning of driver training. Results showed that nonrange students performed significantly better on the following training variables: knowledge posttest (p < 0.01), simulator score (p < 0.01), and driver course grade (p < 0.05). There were no significant differences between range and nonrange students on driver licensing test scores or in the amount of time spent in becoming licensed. However, range students had fewer total accidents than nonrange students (p < 0.05) in the year following the beginning of training. Time spent on the range during training was not related to frequency of accidents or convictions for range students. Cost-benefit aspects of range training were discussed. Range training is operationally less expensive than traditional training, but costs of constructing a driving range may vary appreciably.