Analysis of bus drivers reaction to simulated traffic collision situations - eye-tracking studies

OBJECTIVES

The aim of the study was to establish whether the driver's visual strategy may influence a driver's behavior to avoid a crash in a high-risk situation. Any published papers on drivers' visual strategies just before a crash were not found.

MATERIAL AND METHODS

Tests were performed using a high-tech driving bus simulator. Participants comprised 45 men drivers, aged 43.5±7.9 years old, seniority as a bus driver of 13.3±8.6 years. The tests were preceded by medical examinations: general, neurological and ophthalmological. Each participant drove the same city route for approximately 40 min (entire route - ER). In the final phase, a collision situation was simulated (a phantom car blocked the participant's right of way). Driver's visual strategy was analyzed using the FaceLab device with 2 cameras during ER and just before collision. The field-of-view covered by camera 1 was divided into 8 regions, by camera 2 into 10 regions. The distribution of gazes in regions was a criterion of visual strategy.

RESULTS

Thirty-five drivers completed the simulated driving test, 14 escaped the collision, 21 crashed. These groups differed only in resting systolic blood pressure before the test. The analysis of covariance, after adjusting to this factor, indicated that during the ER visual strategy recorded by camera 1 did not differ between groups, in camera 2 the drivers in the crash group fixed their gaze more frequently (p = 0.049) in region 3 (close part of the road in front of the windshield). Just before the collision drivers who escaped the collision fixed their gaze significantly more often in region 6 (left side of the road) in camera 1 and in region 6 (in front of the windshield,) and region 10 (right side) in camera 2.

CONCLUSIONS

The visual strategy has an impact on the road safety. The analysis of visual strategies may be a useful tool for the training of drivers. Int J Occup Med Environ Health. 2019;32(2):161-74.

Application of eye-tracking in the testing of drivers: A review of research

Recording and analyzing eye movements provide important elements for understanding the nature of the task of driving a vehicle. This article reviews the literature on eye movement strategies employed by drivers of vehicles (vehicle control, evaluation of the situation by analyzing essential visual elements, navigation). Special focus was placed on the phenomenon of conspicuity, the probability of perceiving an object in the visual field and the factors that determine it. The article reports the methods of oculographic examination, with special emphasis on the non-invasive technique using corneal reflections, and the criteria for optimal selection of the test apparatus for drivers in experimental conditions (on a driving simulator) and in real conditions. Particular attention was also paid to the helmet - or glass-type devices provided with 1 or 2 high definition (HD) camcorders recording the field of vision and the direction of gaze, and the non-contact devices comprising 2 or 3 cameras and an infrared source to record eye and head movements, pupil diameter, eye convergence distance, duration and frequency of eyelid blinking. A review of the studies conducted using driver eye-tracking procedure was presented. The results, in addition to their cognitive value, can be used with success to optimize the strategy of drivers training.

[Determination of the corpulence index in newborn infants]

A biometric study of the somatic characteristics weight and stature carried out in 1994 on 5,751 newborn children of both sexes showed the existence of an index of corpulence of the P/T2.75 type which presents the particularity of being correlated to weight and without any link with stature, unlike Quetelet's index (P/T2) and P/T3 Roehrer's index. At fixed stature, the coefficients of the average weight variation are lower than in adults. Moreover, there is no significant difference between the average weight in boys and in girls, their fluctuations being comparable. The expression P/T2.75 allows us to compare the corpulence of newborns of both sexes having distinct weight and stature.

Cardiac responses to maximal anisotonic isometric contractions during handgrip and leg extension

A group of 14-healthy men performed anisotonic isometric contractions (AIC), for 60 s, at an intensity of 100% maximal voluntary contraction force (MVC) during handgrip (HG) and leg extension (LE). Heart rate (fc), stroke volume index (SVI) and cardiac output index (QcI) were measured during the last 10 s of both AIC by an impedance reography method. Force (F) exerted by the subjects was recorded continuously and reported as a relative force (Fr) (% MVC). The F generated during MVC was greater for LE than for HG (502.1 N compared to 374.6 N, P < 0.001). The rate of decrease in Fr was significantly slower for LE than HG for the first 25 s of the exercise (phase 1 of AIC). The Fr developed by the subjects at the end of AIC was 40% MVC for both LE and HG. The increase in fc was greater for LE (63 beats.min-1) than for HG (52 beats.min-1), P < 0.01. The SVI decreased significantly from the resting level by 17.0 ml.m-2 and by 18.2 ml.m-2 for LE and HG, respectively. The QcI increased insignificantly for HG by 0.09 l.min-1.m-2 and significantly for LE by 0.56 l.min-1.m-2 (P < 0.001). It was concluded that although both AIC caused a significant decrease in SVI, greater increases in fc and Qc were observed for LE than for HG. The greater fc and Qc reported during LE was probably related to the greater relative force exerted by LE during phase 1 of AIC. It seems, therefore that central command might have dominated for phase 1 of AIC but that the muscle reflex also contributed significantly to the control of the cardiac response to the high intensity AIC.

[Clinical and ultrasonographic study of uterine involution in postpartum physiology]

The authors monitored the involution of the uterus during the first month after childbirth by means of clinical examinations and abdominal ultrasound. 156 clinical and ultrasound examinations were performed in 77 women on D2, D7 and D28. The size of the uterus and the uterine cavity were measured on the longitudinal sections only. The other incidences, and particularly the axial incidence, made it possible to describe the aspects of the uterine cavity. Uterine involution is rapid during the first week and then slows down. By D28, the dimensions of the uterus have returned to the upper limit for the non-pregnant uterus. During the first week the emptiness line is visible in one out of 13 cases. Hematometra is visible in one out of 6 cases and more frequent on D7 than on D2. It gave rise to no clinical signs. In all cases, an emptiness line was observed on day 28 postpartum.

Aptitude for physical exercise in a population of female hospital workers

The aim of this study was to evaluate the level of physical capacity in a female hospital population of Paris and its suburbs. A total of 1505 women working in the selected departments filled in a questionnaire concerning their working conditions, life habits and health and also attended a medical examination. The effort test performed consisted in flexing the legs 20 times with the chest held straight, in 40 s. The heart rates were measured for the first, the second and the third minutes of recovery (first 15 s multiplied by 4). The blood pressure was measured just after the heart rate, for the first and the third minute. Recovery indices have been constituted from the results. The respective weights of anthropometric and sociodemographic risk factors for recovery indices were studied in multiple logistic regression models. The classification enables us to consider about 25%-30% of our population as having a satisfactory physical capacity, about 26%-27% as having an acceptable capacity, and about 24%-27% as having a weak capacity. About 21% of the population presented an excessive pressure reaction and 44% a questionable pressure reaction. Our results concerning the level of physical capacity of the female nursing staff should be taken into account especially in the future planning of work loads and architectural choices, which must avoid excessive physical burdens in relation to this level. An improvement in the level of physical capacity could be envisaged as well.

Cardiovascular response to static handgrip in trained and untrained men

The influence of aerobic capacity on the cardiovascular response to handgrip exercise, in relation to the muscle mass involved in the effort, was tested in 8 trained men (T) and 17 untrained men (U). The subjects performed handgrip exercises with the right-hand (RH), left-hand (LH) and both hands simultaneously (RLH) at an intensity of 25% of maximal voluntary contraction force. Maximal aerobic capacity was 4.3 l.min-1 in T and 3.21 l.min-1 in U (P less than 0.01). The endurance time for handgrip was longer in T than in U by 29% (P less than 0.05) for RH, 38% (P less than 0.001) for LH and 24% (P less than 0.001) for RLH. Heart rate (fc) was significantly lower in T than in U before handgrip exercise, and showed smaller increases (P less than 0.01) at the point of exhaustion: 89 vs 106 beats.min-1 for RH, 93 vs 100 beats.min-1 for LH and 92 vs 108 beats.min-1 for RLH. Stroke volume (SV) at rest was greater in T than in U and decreased significantly (P less than 0.05) during handgrip exercise in both groups of subjects. At the point of exhaustion SV was still greater in T than in U: 75 vs 57 ml for RH, 76 vs 54 ml for LH and 76 vs 56 ml for RLH. During the last seconds of handgrip exercise, the left ventricular ejection time was longer in T than in U. Increases in cardiac output (Qc) and systolic blood pressure did not differ substantially between T and U, nor between the handgrip exercise tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison between a 30-s all-out test and a time-work test on a cycle ergometer

The relationship between the amount of work (Wlim) performed at the end of constant-power exhausting exercise and exhaustion time (tlim) has been studied for supramaximal exercise [105%, 120%, 135% and 150% of the individual maximal aerobic power, (MAP)] performed on a Monark cycle ergometer in nine men. The Wlim--tlim relationship was described by a linear relationship (Wlim = a + b . tlim). Intercept a was roughly equivalent to the work produced during a 1-min exercise performed at MAP. Slope b was equal to 79% of MAP. Intercept a has been correlated with the total amount of work (AW) performed during a 30-s all-out test supposed to assess anaerobic capacity. Intercept a was significantly (p less than 0.05) correlated with AW. The anaerobic capacity was not depleted at the end of the all-out test, as the mechanical power at the 30th s of this test was approximately equal to twice MAP. However, AW was significantly higher than intercept a. It was likely that the value of intercept a was an underestimation of the maximal anaerobic capacity because of the inertia of the aerobic metabolism. Indeed, an exponential model of the Wlim--tlim relationship, which takes the interia of the aerobic metabolism into account, shows that a linear approximation of the Wlim--tlim relationship yields a systematic underestimation of the anaerobic capacity. Consequently, intercept a of the Wlim--tlim relationship is not a more accurate estimation of the anaerobic capacity than the AW performed during a 30-s all-out test.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of arm position on cardiovascular responses during isometric handgrips

Sixteen subjects (eight women and eight men, age 20-25 years) carried out in the seated position, isometric contractions sustained until exhaustion of the digital flexors. The subject's arm was placed in two positions, high and low. The muscle tensions used were 30, 40 and 50% of maximum voluntary contraction (MVC). Under these conditions, for a given relative force, the duration of contraction (limit-time) was not modified by the arm position. In the male subjects, increases in heart rate (HR) and systolic blood pressure (SBP) were slightly more pronounced in the low than the high position, but the differences were not significant. Limit times in the high position were similar to those in the low position, and, in the absence of an increase in HR and SBP, this seemed to be due to an increase in cardiac output consequent upon a transient improvement in venous return together with an increase in the coefficient of oxygen utilization.

Physiological modifications of local haemodynamic conditions during bilateral isometric contractions

Nine subjects (five women and four men) simultaneously performed two isometric contractions sustained until exhaustion at different relative forces: 40% of maximum voluntary contraction (MVC) for the right elbow flexors; 50% MVC for the left elbow flexors. Contraction of the left elbow flexors commenced at 50% of the limit time (maximum maintenance time) of isometric contraction of the right elbow flexors. Increase in heart rate during concomitant contraction of the left elbow flexors led to an increase in blood flow to the right elbow flexors. Under these conditions, the limit time of isometric contraction of the right elbow flexors was prolonged with respect to the limit time obtained for an isolated isometric contraction at the same relative tension. The difference was more significant in the female (+40%, P less than 0.05) than in the male subjects (+20%, P greater than 0.05).

Comparison of two modalities when exerting isometric contractions

In order to verify whether the method employed to obtain an isometric contraction has any effects on the time for which the contraction can be sustained as well as the consequent cardiocirculatory responses, nine male subjects, from 23 to 42 years of age, carried out isometric contractions of the elbow flexor muscles against either a suspended weight (W) or a fixed strain gauge (SG). The maximum voluntary contraction (MVC) appears to be identical in both instances; and, for a given percentage of MVC, the limit-time of the isometric contraction and its accompanying heart rate changes reveal no significant differences in the two cases.

A trial of evaluating static and dynamic loads in man by means of analysis of the variability of instantaneous heart rate

The instantaneous heart rate changes were examined in 12 forest workers during following tests: increasing (up to refusal) dynamic load on ergometer, rest in erect position, static load (about 75% of body weight) in erect position. The ECG signal, carrying information on heart rate, was amplified and processed by means of an especially designed heart rate analyzer. The dynamics of heart rate changes was evaluated through the analysis of differences of subsequent instantaneous heart rates and of distributions of heart rate accelerations and decelerations during the tests. Significantly different distributions of instantaneous heart rate changes as well as of accelerations and decelerations were observed for different loads.