How reliable are self-report measures of mileage, violations and crashes?

The use of self-reported driver mileage, violations and crashes is very popular in traffic safety research, but their validity has been questioned. One way of testing validity is with an analysis of test–retest reliability. Three mechanisms might influence reliability in self report; actual changes in the variable over time, stable systematic reporting bias, and random error. Four samples of drivers who had responded twice to an online questionnaire asking them to report their mileage, violations and crashes were used and correlations between self reports for this data were calculated. The results for crashes were compared to expected correlations, calculated from the error introduced by the non-overlapping periods and the variable means. Reliability was fairly low, and controlling for mileage in the violations and crashes calculations did not strengthen the associations. The correlation between self reports of crashes in different time periods was found to be much larger than expected in one case, indicating a report bias, while the other correlation agreed with the predicted value. The correlations for overlapping time periods were much smaller than expected. These results indicate that drivers’ self reports about their mileage, violations and crashes are very unreliable, but also that several different mechanisms are operating. It is uncertain exactly under what circumstances different types of self report bias is operating. Traffic safety researchers should treat the use of self-reported mileage, violations and crashes with extreme caution and preferably investigate these variables with the use of objective data

Unemployment alters the set-point for life satisfaction

According to set-point theories of subjective well-being, people react to events, but then return to initial levels of happiness and satisfaction over time. We test this idea by examining reaction and adaptation to unemployment in a 15-year longitudinal study. In accordance with set-point theory, individuals first reacted strongly to unemployment and then shifted back toward their former (or “baseline”) levels of life satisfaction. However, on average, individuals did not completely return to their former levels of life satisfaction, even after they became re-employed. The findings suggests that even a short period of unemployment can cause an alteration in a person’s long-term set-point. Within-person analyses showed, however, that there are considerable individual differences in reaction and adaptation to unemployment. Although there was substantial stability in life satisfaction over the years, unemployment did influence long-term levels, thus suggesting that in addition to personality, long-term subjective well-being can also be influenced by life circumstances

On the Viability of a Non-Analytical f(R)-Theory

In this paper, we show how a power-law correction to the Einstein-Hilbert action provides a viable modified theory of gravity, passing the Solar-System tests, when the exponent is between the values 2 and 3. Then, we implement this paradigm on a cosmological setting outlining how the main phases of the Universe thermal history are properly reproduced. As a result, we find two distinct constraints on the characteristic length scale of the model, i.e., a lower bound from the Solar-System test and an upper one by guaranteeing the matter dominated Universe evolution.Comment: 9 pages, 2 figure

Violation of the London Law and Onsager-Feynman quantization in multicomponent superconductors

Non-classical response to rotation is a hallmark of quantum ordered states such as superconductors and superfluids. The rotational responses of all currently known single-component "super" states of matter (superconductors, superfluids and supersolids) are largely described by two fundamental principles and fall into two categories according to whether the systems are composed of charged or neutral particles: the London law relating the angular velocity to a subsequently established magnetic field and the Onsager-Feynman quantization of superfluid velocity. These laws are theoretically shown to be violated in a two-component superconductor such as the projected liquid metallic states of hydrogen and deuterium at high pressures. The rotational responses of liquid metallic hydrogen or deuterium identify them as a new class of dissipationless states; they also directly point to a particular experimental route for verification of their existence.Comment: Nature Physics in print. This is an early version of the paper. The final version will be posted 6 months after its publication Nature Physics, according to the journal polic

Apprehension and interest: Therapist and student views of the role emerging placement model in the Republic of Ireland

Purpose - Role-emerging placements have been used internationally within occupational therapy education but are relatively new to Ireland. At times, there has been a debate in the profession regarding the use of this placement model. This paper aims to generate views from both occupational therapists and occupational therapy students on the use of role-emerging placements in the Republic of Ireland. Design/methodology/approach - Electronic surveys were administered to occupational therapy students and occupational therapists in Ireland. Quantitative data were analysed using the SPSS Statistics software package and the content of the open question responses were analysed into themes. Findings - Occupational therapists (n = 60) and occupational therapy students (n = 45) indicated that there were inconsistent views surrounding role-emerging placements. It is deemed as an effective method for student learning, but apprehension exists around inclusion within occupational therapy programmes in the Republic of Ireland. Preference was indicated towards inclusion of role-emerging placements on a part-time basis within formal occupational therapy education. Originality/value - Both respondent groups viewed that role-emerging placements can positively influence new areas of occupational therapy practice and concern over the use of the placement model requires further exploration and debate. This study is from an Irish context, although there are similarities with other countries’ use of the placement model. There is a need for research through an in-depth exploration of the learning experience of undertaking role-emerging placements from the students’ perspective and identification of supports required to promote an optimal learning experience

Comparisons of predictive power for traffic accident involvement; Celeration behaviour versus age, sex, ethnic origin, and experience

Driver celeration behaviour theory (DCBT) assumes that risk for a driver of causing a road crash is linearly related to speed change in any given moment and that the speed change variable (celeration) captures all risk (all vehicle control movements can be measured as acceleration). When sampling driver behaviour, the celeration variable is calculated as the average of all absolute values of acceleration when the vehicle is moving. DCBT predicts that no other variable can be a stronger predictor of (the same set of) traffic accident involvements than celeration, given equal reliability of the predictors. Also, other predictors, regardless of which ones, should associate with celeration in ways that are similar to how they correlate with accidents. Predictions were tested in a sample of bus drivers, against variables with reliabilities close to 1 (age, sex, experience, ethnic origin), which are not necessarily optimal predictors for testing but were the only predictors available. The results were largely as predicted from theory. The principles for testing the kind of predictions made from celeration theory were discussed, outlining the importance of a larger number of variables, preferably with repeated measurements

The effect of driver improvement interventions on crash involvement; has it been under-estimated?

The available evidence suggests that driver improvement interventions (with the aim to increase driver safety, most often by education or training) do not work. The average effect calculated in several meta-analyses is close to, and not always possible to distinguish from, zero, despite total samples sizes of several hundred thousand drivers. However, it is possible that all studies included in these meta-analyses have under-estimated the effect, due to a methodological error; all crashes have been used as dependent variable, instead of only those that the targeted drivers have caused. This error is expected to have considerably deflated the effect sizes, but it is not known how large this effect could be. Using crash data for bus drivers in which culpability had been reliably established, a simple simulation was performed to determine the difference between using culpable and all crashes as an estimator of a safety effect. Using data for six years, calculations were made on single years. About ten percent of culpable crashes in each year were deleted to simulate a safety effect, where after the difference between the original and the simulated variable were calculated, using culpable only and all crashes in parallel. The effects using these two different kinds of datasets could then be compared and the under-estimation effect estimated. Culpable crashes, as compared to all crashes, yielded larger differences in means between time periods, and smaller standard deviations. In between-subjects comparisons resulted in 15–30 percent larger effects for culpable crashes. Within-subjects calculations yielded larger but not as systematic effects. The effect of driver improvement on crash involvement has been systematically under-estimated, as extremely few evaluation studies seem to have taken culpability for crashes into account. Therefore, new evaluations need to be undertaken, and/or old data re-analysed, to calculate a better estimate of the true effect of training and education in driving safety

Fuel efficient driving training - state of the art and quantification of effects

A new area of traffic education, training in fuel efficient driving, is reviewed. This training is often said to reduce fuel consumption, accidents, emissions, and wear and tear on vehicles. These claims, made mainly by educators and bureaucrats, and said to have scientific backing, are found to be wanting; most of the possible effects are totally unsubstantiated, while the most central, reduction in fuel consumption, is well below the highest figures mentioned. Research problems and general methodology regarding the variable of fuel consumption reduction are discussed. Although it is fairly easy to show the large potential of training under experimental conditions, it is rather complicated in a field setting. However, it is necessary to study the effects in the drivers' natural environment, because of the many possible sources of error in controlled settings which tend to inflate the effect. What is possible during training should therefore rather be seen as a maximum of what can be achieved, while the effect in real life driving is usually far below. Being a new area of research, it is uncertain exactly how effects should be measured, apart from fuel consumption. This problem is discussed and the results from a quantification of effects of training in fuel efficient driving are presented. The changes in driving style are described in terms of acceleration patterns; mean accelerations (over time) increased and mean decelerations decreased, while the time spent on a stable velocity decreased. Also, the mean acceleration and deceleration over distance was fairly well correlated with fuel consumption, and very clear differences could be seen on several acceleration-related variables as a result of training. These results show that acceleration patterns are a workable way of quantifying this type of training

The impact of low energy proton damage on the operational characteristics of EPIC-MOS CCDs

The University of Tübingen 3.5 MeV Van de Graaf accelerator facility was used to investigate the effect of low energy protons on the performance of the European Photon Imaging Camera (EPIC), metal–oxide semiconductor (MOS), charge coupled devices (CCDs). Two CCDs were irradiated in different parts of their detecting areas using different proton spectra and dose rates. Iron-55 was the calibration source in all cases and was used to measure any increases in charge transfer inefficiency (CTI) and spectral resolution of the CCDs. Additional changes in the CCD bright pixel table and changes in the low X-ray energy response of the device were examined. The Monte Carlo code Stopping Range of Ions in Matter (SRIM) was used to model the effect of a 10 MeV equivalent fluence of protons interacting with the CCD. Since the non-ionising energy loss (NIEL) function could not be applied effectively at such low proton energies. From the 10 MeV values, the expected CTI degradation could be calculated and then compared to the measured CTI changes