Optical illusions and life-threatening traffic crashes: A perspective on aerial perspective

Improved stereo perception in coronary angiography using the X-ray tube as the viewpoint and validation with 3D printed models

Coronary angiography (CAG) provides two-dimensional images, but a clinician who is experienced in percutaneous coronary interventions can use information from these images to interpret spatial depth and infer the three-dimensional (3D) locations of vessels. We hypothesized that CAG results were equivalent to the mirror image of a coronary artery perspective projection, and a stereo perception could be easily established when the viewpoint of the angiogram was the X-ray tube instead of the detector. To eliminate the influence of heartbeat and respiration, a 3D-printed a coronary artery model was constructed for analysis. The effects of gantry movements during digital subtraction angiography (DSA) on the image were used to identify factors that affected DSA image transformation. Then, based on these factors, DSA imaging was simulated using UG NX software with three methods: (i) a perspective projection with the detector as the viewpoint; (ii) a parallel projection; and (iii) a mirror image of the perspective projection with the X-ray tube as the viewpoint. Finally, the resulting 3D images were compared with the DSA image. Our mirror image of the coronary artery perspective projection that used the X-ray tube as the viewpoint fused precisely with the CAG results and provided exact simulations of all the effects of DSA gantry movements on the DSA image. CAG results were equivalent to the mirror image of coronary artery perspective projection, and the stereo perception was easily established using the X-ray tube as the viewpoint.

Judgments of Object Size and Distance across Different Virtual Reality Environments: A Preliminary Study

Emerging technologies offer the potential to expand the domain of the future workforce to extreme environments, such as outer space and alien terrains. To understand how humans navigate in such environments that lack familiar spatial cues this study examined spatial perception in three types of environments. The environments were simulated using virtual reality. We examined participants’ ability to estimate the size and distance of stimuli under conditions of minimal, moderate, or maximum visual cues, corresponding to an environment simulating outer space, an alien terrain, or a typical cityscape, respectively. The findings show underestimation of distance in both the maximum and the minimum visual cue environment but a tendency for overestimation of distance in the moderate environment. We further observed that depth estimation was substantially better in the minimum environment than in the other two environments. However, estimation of height was more accurate in the environment with maximum cues (cityscape) than the environment with minimum cues (outer space). More generally, our results suggest that familiar visual cues facilitated better estimation of size and distance than unfamiliar cues. In fact, the presence of unfamiliar, and perhaps misleading visual cues (characterizing the alien terrain environment), was more disruptive than an environment with a total absence of visual cues for distance and size perception. The findings have implications for training workers to better adapt to extreme environments.

Population-based case-control study of the effect of sun glare on pedestrian fatalities in Taiwan

OBJECTIVES

Sun glare is a serious driving hazard and increases crash risks. Relatively few studies have examined the effects of sun glare on pedestrian fatalities, given that a crash has occurred. The primary objective of this study was to investigate the effect of sun glare on pedestrian fatalities.

DESIGN

A population-based case-control study.

SETTING

Taiwan.

PARTICIPANTS

Using the Taiwan National Traffic Crash Data and sunrise and sunset data from the National Oceanic and Atmospheric Administration for the period 2003 to 2016, 100 411 pedestrians involved in crashes were identified. Of these crashes, 13 355 and 87 056 were glare-related (case) and non-glare-related (control) crashes, respectively.

METHODS

To account for unobserved heterogeneity, mixed logit models were estimated to identify the determinants of pedestrian fatalities.

MAIN OUTCOME MEASURES

Pedestrian fatalities.

RESULTS

Pedestrians involved in glare-related crashes were more likely to be fatally injured than those in non-glare-related crashes (β=0.527; t=3.21). Other contributory factors to fatal injuries among pedestrians were older pedestrians (β=0.553; t=2.33), male drivers (β=0.324; t=2.33), older drivers (β=0.218; t=2.14), intoxicated motorists (β=0.606; t=2.85), rural roadways (β=0.985; t=3.92), overtaking manoeuvres (β=0.472; t=3.58), heavy vehicle crash partners (β=0.248; t=2.78) and sunset hours (β=0.274; t=3.08). Walking against traffic appeared beneficial for decreasing injury severity (β=-0.304; t=-2.76).

CONCLUSIONS

Sun glare is associated with pedestrian fatalities. Older pedestrians, male drivers, older drivers and intoxicated motorists are prevalent determinants of pedestrian fatalities in glare-related crashes.