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PubMed1986

Relating the effect of safety measures to expected number of accidents.

Traffic engineers have long believed that the effectiveness (percentage reduction in accidents) of a safety measure is greater at locations which had many accidents than at those which had few. That this type of belief has often translated into warrants is evidence of the strength of this belief. Recent research has raised doubts as to whether this phenomenon is real or merely a manifestation of regression-to-the-mean. This paper addresses this issue in the context of an examination of the safety effect of converting 222 intersections in Philadelphia, PA, U.S.A. from two-way to all-way stop control. The results indicate that the conversions were more effective at intersections expected to have many accidents than at the relatively safe intersections. One of the important implications of this finding is that, for measures for which this phenomenon exists, effectiveness cannot be specified as a single accident reduction factor as is currently the practice.

Accidents, Traffic↗

PubMed1993

Development of a collision typology for evaluation of collision avoidance strategies.

This paper summarizes the results of an effort to identify and rank vehicle collision scenarios in order to create a "collision typology" that could aid in the assessment of the potential benefit of accident avoidance technologies. Data from four computerized accident files were used to construct an 18-level collision configuration variable. This variable includes the number of vehicles involved, their relative orientation, intent to turn, relation to intersection, and traffic control at the intersection. Distributions of the collision configuration variable were generated for several factors of interest using 1989 Michigan data. Five of the most prevalent collision types were selected for more detailed review based on the original police accident reports. The case studies lent additional insight into the circumstances of different accident types. Among other findings, the review suggested that in collisions at nonsignalized intersections, older drivers often stopped and then pulled out into oncoming traffic, while younger drivers more often failed to stop at all.

Accident Prevention↗

PubMed1996

Bicycle accidents and drivers' visual search at left and right turns.

The accident data base of the City of Helsinki shows that when drivers cross a cycle path as they enter a non-signalized intersection, the clearly dominant type of car-cycle crashes is that in which a cyclist comes from the right and the driver is turning right, in marked contrast to the cases with drivers turning left (Pasanen 1992; City of Helsinki, Traffic Planning Department, Report L4). This study first tested an explanation that drivers turning right simply focus their attention on the cars coming from the left-those coming from the right posing no threat to them-and fail to see the cyclist from the right early enough. Drivers' scanning behavior was studied at two T-intersections. Two well-hidden video cameras were used, one to measure the head movements of the approaching drivers and the other one to measure speed and distance from the cycle crossroad. The results supported the hypothesis: the drivers turning right scanned the right leg of the T-intersection less frequently and later than those turning left. Thus, it appears that drivers develop a visual scanning strategy which concentrates on detection of more frequent and major dangers but ignores and may even mask visual information on less frequent dangers. The second part of the study evaluated different countermeasures, including speed humps, in terms of drivers' visual search behavior. The results suggested that speed-reducing countermeasures changed drivers' visual search patterns in favor of the cyclists coming from the right, presumably at least in part due to the fact that drivers were simply provided with more time to focus on each direction.

Accidents, Traffic↗

PubMed1993

Changes in motor planning during the acquisition of movement patterns in a continuous task.

Changes in the planning and execution of movements were studied as a function of practice on a continuous motor task. Twelve subjects learned to move a pen through a cut-out square and maze patterns with their eyes closed. Maze patterns consisted of six, eight, ten, or twelve segments that were connected by intersections. Task performance was studied during six blocks. Although the mazes could be traced continuously in a clockwise direction, selecting a wrong turn at an intersection resulted in coming to a dead end. Performance at intersections was analyzed by determining the number of correct (and incorrect) turns following mechanically forced stops and the number of correctly planned and executed turns without any halt. In addition, movement time and pause duration were analyzed. With practice an increase in the number of correctly executed turns indicated that subjects gradually learned to group segments into chunks of increasing size. It was found that up to eight segments could be organized and executed as a single unit. Finally, with practice a non-linear performance improvement was found, suggesting that the learning process proceeded through qualitatively different learning stages. It is concluded that within five minutes subjects gradually changed their movement strategy from a sequential, trial-and-error mode in which planning and execution occurred segment by segment, to a mode in which concurrent planning was realized, i.e. in which the planning of oncoming segments occurred concurrently with the execution of segments.

Adult↗

PubMed1990

A field evaluation of driver eye and head movement strategies toward environmental targets and distractors.

A new systems approach for evaluating field performance of drivers is presented in a practical experimental demonstration. The emphasis reflected in this paper is on driver head and eye movement behaviour toward environmental targets and distractors. A unique video technology set-up was designed to record eye and head movements. Simultaneous video-tapings of driver eye/head movements and the environmental scene were time synchronised. Two intersections (one busy and one quiet) were carefully selected and analysed for their static and dynamic visual targets and distractors. A subject made 40 repetitive left-turns alternately at busy and quiet intersections in a naturally moving traffic environment. Both head movement patterns and eye movement frequencies differed significantly between the two intersections. Results suggest that the eye and head movements are highly dependent upon the type of turn configuration, type and frequency of targets, type and frequency of distractors, and traffic control configurations.

Journal Article↗

PubMed1986

Structures of the carbohydrate moiety attached to one site in the first domain of turkey ovomucoid: elucidation by 1H-n.m.r. spectroscopy.

1H-N.m.r. spectroscopy was used to elucidate the primary structures of the carbohydrate moiety attached to asparagine at residue 53 in the first domain of turkey ovomucoid, a serine proteinase inhibitor. The carbohydrate moiety is a heterogeneous mixture of three structurally closely related complex-type oligosaccharides. Of the total carbohydrate moiety, 61% is tetra-antennary with terminal galactose and with an intersecting N-acetylglucosamine, and containing an additional N-acetylglucosamine (10') attached to mannose (4'). Another 23% is tri-antennary with terminal galactose and with an intersecting N-acetylglucosamine. The remaining 16% is tri-antennary with terminal galactose (6 and 8 only), with an intersecting N-acetylglucosamine.

Amino Acid Sequence↗

PubMed1995

Tensile stress-strain characteristics of the human meniscal material.

The nonlinear stress-strain characteristics of the human menisci were determined by uniaxial elongation tests performed on circumferential and radial specimens prepared from different regions, layers, and locations. The properties of the collagen fibers and the matrix were calculated using the test results along with the values of the volume fractions of the meniscal components. Regression analysis showed that only three parameters, the elastic modulus, the maximum strain, and the strain intersect, are sufficient to define the nonlinear stress-strain relation up to failure. For radial specimens, the layer had a significant effect (p < 0.01) on the elastic modulus and the maximum strain, but had no effect on the strain intersect and the maximum stress. For the same specimens, the region had a significant effect (p < 0.01) only on the strain intersect and the maximum stress. For circumferential specimens, analysis indicated no significant effect of either the region, the layer, or the location of the specimens on the material parameters defining the stress-strain relation.

Adult↗

PubMed1990

The application of enzyme kinetics to the determination of dissociation constants for antigen-antibody interactions in solution.

The binding in ELISA procedures of a soluble antigen to a coated antibody in the presence of a second soluble antibody of different epitope specificity can formally be described by a mathematical model, identical to the one describing the random association between enzyme and substrate in a two substrate enzyme system. At low antigen levels, the concentration of both the coated and soluble (monoclonal) antibody, present in molar excess, can be varied and the resulting ternary complex can be detected directly or indirectly. Double reciprocal plots of the ELISA signal versus antibody concentrations yield straight intersecting lines. From the intersection, functional dissociation constants in solution can be determined. Alternatively, when the antigen is too small to accommodate two antibodies or when the binding affinities are low, the antibody of interest can both be insolubilized and at the same time be present in solution as a secondary antibody. In the presence of antigen, the coated and soluble antibody will compete for the same epitope, without formation of a ternary complex. On changing the concentration, both of coated and of soluble antibody, reciprocal plots of the bound antigen signal versus the concentration of competing antibody result in linear relationships yielding an intersection from which the functional antigen-antibody dissociation constant can be calculated.

Animals↗

PubMed1993

Locating the periapical region in dental radiographs using digital image analysis.

An algorithm was designed to automatically obtain information on the orientation of roots in dental radiographs aimed at localizing the periapical region. A curve was approximated mathematically by a cubic polynomial to intersect the boundary of the root at its apex. The performance was judged by comparing the location of this intersection with the actual location of the apex as determined by five expert observers. In an experiment with 262 roots of the eight tooth groups, the distance between these two points was less than 1 mm in 67.9% of all cases and less than 2 mm in 88.2%. The performance of the procedure appeared to depend on the tooth group (p < 0.01). The location of the intersection was reproducible within 1 mm in 86.4% of all cases. The reproducibility was, however, not equal for all tooth groups (p < 0.01). The experts were more consistent in localizing the apex than the system was (p < 0.01), although this difference was not confirmed for four of the tooth groups (p > 0.57), and was marginal for two others (0.01 < p < 0.02). It is concluded that the algorithm is promising in its capacity to track a majority of roots down to their apex. It could therefore add important knowledge to imaging procedures aimed at the digital analysis of the periapical region.

Algorithms↗

PubMed1992

Acute, but not chronic, exercise lowers the body weight set-point in male rats.

The influence of muscular training on overall energy balance and body weight is not clear. A group of male rats was trained to feed every day from 1000 to 1200. Then the intersect of regression line of food hoarded during meal time vs. body weight with the X-axis was measured. Finally, the rats were trained to run 1 h every day on a motor-driven treadmill. When the training took place in the morning, just before the hoarding session, the mean intersect was significantly lowered from control (497 +/- 18 g to 433 +/- 9 g). When the training took place in the afternoon, after the hoarding session, the mean intersect was not significantly different (504 +/- 21 g) from control. Food intake during the hoarding sessions was affected neither by body weight changes nor by muscular exercise. These results suggest that the set-point for body weight regulation is acutely lowered just after muscular exercise, but is not influenced by chronic training.

Animals↗

PubMed1991

Longitudinal Gompertzian analysis of pancreatic cancer mortality in the U.S., 1962-1987: distinguishing between competitive and environmental influences upon evolving mortality patterns.

Pancreatic cancer (PanC) is an extraordinarily lethal neoplasm that is currently the fifth leading cause of cancer death in the United States. Annual age-specific mortality rates for PanC in the U.S. from 1962 to 1987 were subjected to longitudinal Gompertzian analysis. Age-specific PanC mortality rate distributions between age 30 and 60 years were determined by a common fixed intersect point and a variable competitive factor. The intersect point for PanC occurred at age 59.5 years and mortality rate 37.4 per 100,000 for men, and at age 53.2 years and mortality rate 7.9 per 100,000 for women. These intersect points are determined by genetic and environmental influences upon mortality. The observation that these points have remained fixed suggests that there has been no significant alteration in environmental etiopathogenic influences upon PanC mortality. Longitudinal Gompertzian analysis suggests that the emergence of PanC in the U.S. as a significant cause of cancer mortality has been the consequence of competitive influences upon PanC mortality dynamics.

Adult↗

PubMed1995

Longitudinal Gompertzian analysis of Parkinson's disease mortality in Japan, 1950-1993.

Age-specific mortality rates from Parkinson's disease (PD) in Japan from 1950 through 1993 were subjected to longitudinal Gompertzian analysis. Age-specific PD mortality rate distributions between age 45 and 75 years were determined by a common fixed intersection point and a variable competitive factor. The intersection point for PD occurred at age 65.36 years and mortality rate 2.45 per 100,000 for men, and at age 65.49 years and mortality rate 2.12 per 100,000 for women from 1950-1951 to 1992-1993. The increase in PD mortality is due entirely to rapidly increasing age-specific mortality rates at ages greater than the intersection points for both sexes. Longitudinal Gompertzian analysis suggests that the rising mortality from PD has been the consequence of competitive influences upon PD mortality dynamics.

Age Factors↗

PubMed1990

Fast algorithm for generating CPK images on graphics workstations.

An algorithm for generating CPK images of molecules is presented that uses bitmap operations to solve the hidden-surface problem. The algorithm makes certain assumptions: that the size and shading of each atom are determined only by its type and are unaffected by the atom's position, and that an intersection table comprised of entries for all pairs of atoms whose radii intersect is available. For speed, bitmaps of shaded and colored atom disks are predrawn. The atoms are projected from back to front. Atom intersections are explicitly calculated and used to generate mask bitmaps that are then used to truncate the predrawn disks, leaving the visible portions of the atom disks.

Algorithms↗

PubMed2006

On the nature of over-dispersion in motor vehicle crash prediction models.

Statistical modeling of traffic crashes has been of interest to researchers for decades. Over the most recent decade many crash models have accounted for extra-variation in crash counts--variation over and above that accounted for by the Poisson density. The extra--variation--or dispersion--is theorized to capture unaccounted for variation in crashes across sites. The majority of studies have assumed fixed dispersion parameters in over-dispersed crash models--tantamount to assuming that unaccounted for variation is proportional to the expected crash count. Miaou and Lord [Miaou, S.P., Lord, D., 2003. Modeling traffic crash-flow relationships for intersections: dispersion parameter, functional form, and Bayes versus empirical Bayes methods. Transport. Res. Rec. 1840, 31-40] challenged the fixed dispersion parameter assumption, and examined various dispersion parameter relationships when modeling urban signalized intersection accidents in Toronto. They suggested that further work is needed to determine the appropriateness of the findings for rural as well as other intersection types, to corroborate their findings, and to explore alternative dispersion functions. This study builds upon the work of Miaou and Lord, with exploration of additional dispersion functions, the use of an independent data set, and presents an opportunity to corroborate their findings. Data from Georgia are used in this study. A Bayesian modeling approach with non-informative priors is adopted, using sampling-based estimation via Markov Chain Monte Carlo (MCMC) and the Gibbs sampler. A total of eight model specifications were developed; four of them employed traffic flows as explanatory factors in mean structure while the remainder of them included geometric factors in addition to major and minor road traffic flows. The models were compared and contrasted using the significance of coefficients, standard deviance, chi-square goodness-of-fit, and deviance information criteria (DIC) statistics. The findings indicate that the modeling of the dispersion parameter, which essentially explains the extra-variance structure, depends greatly on how the mean structure is modeled. In the presence of a well-defined mean function, the extra-variance structure generally becomes insignificant, i.e. the variance structure is a simple function of the mean. It appears that extra-variation is a function of covariates when the mean structure (expected crash count) is poorly specified and suffers from omitted variables. In contrast, when sufficient explanatory variables are used to model the mean (expected crash count), extra-Poisson variation is not significantly related to these variables. If these results are generalizable, they suggest that model specification may be improved by testing extra-variation functions for significance. They also suggest that known influences of expected crash counts are likely to be different than factors that might help to explain unaccounted for variation in crashes across sites.

Accidents, Traffic↗

PubMed2006

Short-term effects of countermeasures for improved safety and mobility at marked pedestrian crosswalks in Borås, Sweden.

The Swedish code concerning car drivers' responsibility to give way to pedestrians was strengthened in 2000. The primary aim of this study is to evaluate the short-term effects of the change in code. Another goal is to look at the effects of the reconstruction of four sites in Borås, Sweden. One site had changes made prior to the change of code, two test sites had countermeasures implemented during the study, and one comparison site was left unchanged. All the sites were chosen because schools were situated nearby. The focus of the evaluation was on children and elderly as pedestrians and cyclists. The goal of traffic calming of a 90 percentile driving speed below 30 km/h was not fulfilled at any of the test sites. A conclusion is that the height of a speed cushion is important. After the speed cushions were lowered from 70 mm to 55 mm, the 90 percentile speed increased from 34 km/h to 41 km/h. Sites with no speed cushions had much higher speeds. The design of an intersection influences road users' behavior. At the site where one crosswalk was removed, pedestrians that were using the remaining marked crosswalk were given way to less frequently than at the other sites. At intersections where most pedestrians used marked crosswalks, the children benefited the most in mobility. At the intersection where pedestrians used marked crosswalks to a lower extent after reconstruction, children and the elderly had the smallest increase in frequency of being given way to. After reconstruction to a court-yard street, the pedestrians were given way to a lower extent compared with the other sites, though the vehicle speeds were the lowest observed at this study. At the sites were no physical changes were made, the change of code improved driver yield behavior, but no more towards children than other age groups.

Accident Prevention↗

PubMed2006

Safety effects of roundabouts in Flanders: signal type, speed limits and vulnerable road users.

This paper examines the road safety effects of roundabouts built in Flanders between 1994 and 2000. While the overall effect is positive (39% reduction of injury accidents), the results vary considerably with the speed limit on the main and adjacent road (the higher, the more effective) and the pre-roundabout signalization of the intersection (32% reduction with traffic lights versus 44% without). However, microscopic analysis reveals that roundabouts are not always effective. Serious injury accidents are estimated to increase by 117% on 70 km/h x 50 km/h intersections equipped with signalization before the roundabout. The number of injury accidents involving vulnerable road users is also found to increase (28%) on 50 km/h x 50 km/h junctions that were originally signalized. Moreover, the vulnerable road user is more likely to get fatally or seriously injured. Therefore, it is concluded that traffic lights protect vulnerable road users more effectively than roundabouts, which, in turn, are superior to intersections without signalization.

Acceleration↗

PubMed2003

The joint.

Some concave volumes are perceived as compositions of joined objects. Joined objects are optically undetermined, being compatible with three possible solutions: an empty intersection volume bounded by two indented objects; an intersection volume entirely filled-in by parts of two indented objects; a totally convex object joined to an indented object (the solution preferred by most perceivers). Knowledge of material penetrability does not predict 3D amodal completion. To identify relevant factors we selected different compositions and ran a multiple-regression analysis of completion choices. After eliminating colour, we considered six spatial factors: relative position along the vertical, relative size, orientation, proximity to the observer, minimization of completed parts, support relationship. The first two factors played a major role. The comparison of choices by upright versus inverted observers indicated that relative position along the vertical depends more on gravitational than egocentric coordinates. In conclusion, when relative spatial position and relative size cooperate, amodal completion of intersecting solids generates strong effects, which can overcome logical expectations.

Adult↗

PubMed2006

Mathematical analysis of trabecular 'trajectories' in apparent trajectorial structures: the unfortunate historical emphasis on the human proximal femur.

Wolff's "law" of the functional adaptation of bone is rooted in the trajectory hypothesis of cancellous bone architecture. Wolff often used the human proximal femur as an example of a trajectorial structure (i.e. arched trabecular patterns appear to be aligned along tension/compression stress trajectories). We examined two tenets of the trajectory hypothesis; namely, that the trabecular tracts from the tension- and compression-loaded sides of a bending environment will: (1) follow 'lines' (trajectories) of tension/compression stress that resemble an arch with its apex on a neutral axis, and (2) form orthogonal (90 degrees ) intersections. These predictions were analysed in proximal femora of chimpanzees and modern humans, and in calcanei of sheep and deer. Compared to complex loading of the human femoral neck, the chimpanzee femoral neck reputedly receives relatively simpler loading (i.e. temporally/spatially more consistent bending), and the artiodactyl calcaneus is even more simply loaded in bending. In order to directly consider Wolff's observations, measurements were also made on two-dimensional, cantilevered beams and curved beams, each with intersecting compression/tension stress trajectories. Results in the calcanei showed: (1) the same nonlinear equation best described the dorsal ("compression") and plantar ("tension") trabecular tracts, (2) these tracts could be exactly superimposed on the corresponding compression/tension stress trajectories of the cantilevered beams, and (3) trabecular tracts typically formed orthogonal intersections. In contrast, trabecular tracts in human and chimpanzee femoral necks were non-orthogonal (mean approximately 70 degrees ), with shapes differing from trabecular tracts in calcanei and stress trajectories in the beams. Although often being described by the same equations, the trajectories in the curved beams had lower r(2) values than calcaneal tracts. These results suggest that the trabecular patterns in the calcanei and stress trajectories in short beams are consistent with basic tenets of the trajectory hypothesis while those in human and chimpanzee femoral necks are not. Compared to calcanei, the more complexly loaded human and chimpanzee femoral necks probably receive more prevalent/predominant shear, which is best accommodated by non-orthogonal, asymmetric trabecular tracts. The asymmetrical trabecular patterns in the proximal femora may also reflect the different developmental 'fields' (trochanteric vs. neck/head) that formed these regions, of which there is no parallel in the calcanei.

Adaptation, Physiological↗