Traffic calming design--a speed management method. Danish experiences on environmentally adapted through roads.

The Danish Road Directorate has conducted an experiment on traffic calming in three pilot towns. The problems caused by through traffic were reduced by using the new traffic management method called "Environmentally adapted through road." By using different kinds of speed reducing measures, vehicle speeds were slowed down. Priority was given to the local town environment, pedestrians, and cyclists. The aim was to increase safety, reduce the feeling of insecurity, and improve the local town environment. An extensive effect evaluation study programme was worked out by engineers together with architects, psychologists, economists, and biologists. The evaluation study included speeds, accidents, fence effect for pedestrians and cyclists, delays for through-going cars and side-road drivers, retail trade, noise and air pollution, energy consumption, costs, and users' opinions. The results show that vehicle speeds have been reduced significantly in the three pilot towns. The feeling of security and traffic safety have been increased. The town environments have been improved and the towns have become more attractive from the citizens' point of view.     

Crash reduction following installation of centerline rumble strips on rural two-lane roads

Rural two-lane roads generally lack physical measures such as wide medians or barriers to separate opposing traffic flows. As a result, a major crash problem on these roads involves vehicles crossing the centerline and either sideswiping or striking the front ends of opposing vehicles. These types of opposing-direction crashes account for about 20% all fatal crashes on rural two-lane roads and result in about 4500 fatalities annually in the US. The present study evaluated a potential engineering countermeasure for such crashes—installation of rumble strips along the centerlines of undivided rural two-lane roads to alert distracted, fatigued, or speeding motorists whose vehicles are about to cross the centerlines and encroach into opposing traffic lanes. Data were analyzed for approximately 210 miles of treated roads in seven states before and after installation of centerline rumble strips. An empirical Bayes before–after procedure was employed to properly account for regression to the mean while normalizing for differences in traffic volume and other factors between the before and after periods. Overall results indicated significant reductions for all injury crashes combined (14%, 95% confidence interval (95% CI)=5–23%) as well as for frontal and opposing-direction sideswipe injury crashes (25%, 95% CI=6–44%)—the primary target of centerline rumble strips. In light of their effectiveness and relatively low installation costs, consideration should be given to installing centerline rumble strips more widely on rural two-lane roads to reduce the risk of frontal and opposing-direction sideswipe crashes.     

Experimental research on the effectiveness and adaptability of speed reduction markings in downhill sections on urban roads: A driving simulation study

The objective of this paper is to test the effectiveness and adaptability of speed reduction markings (SRMs) in downhill sections on urban roads with distinct roadway grades. Empirical data including vehicle speed and acceleration were collected in a driving simulator. Subjective questionnaires were conducted, and two indexes – the relative speed difference and standard deviation of acceleration – were developed to evaluate the effectiveness and adaptability of SRMs. Meanwhile, the effectiveness of driving simulator related to different road alignments and types of SRMs has been validated through a field test. Results of subjective questionnaires showed that the majority of subjects had no feelings of nervousness, but they were affected by SRMs while driving through downhill sections in all four scenarios (i.e., downhill sections with vertical grades of 3, 2, 1.5 and 1%). In terms of vehicle speed and acceleration, the results of the analysis of variance (ANOVA) and the contrast analysis (S–N–K method) indicated that SRMs were significantly effective when roadway grades of downgrade sections were 1.5, 2 and 3%, while transverse speed reduction markings (TSRMs) had significantly worse adaptability (P < 0.05). Therefore, this research recommends that TSRMs could be placed in downhill sections with roadway grades of 1.5 or 2%; longitudinal speed reduction markings (LSRMs) could be placed in downhill sections with a roadway grade of 3%. Whether SRMs are placed in downhill sections with a roadway grade of 1% would depend on other factors such as financial issues and crash records, which are not considered in this paper.     

Dispersion reduction in pressure-driven flow through microetched channels

Fluid is often moved about microetched channels in lab-on-a-chip applications using electrokinetic flows (electrophoresis or electroosmosis) rather than pressure-driven flows because the latter result in large Taylor dispersion. However, small pressure gradients may arise unintentionally in such systems due to a mismatch in electroosmotic flow rates or hydrostatic pressure differentials along the microetched channel. Under laminar flow conditions, Doshi et al. (Chem. Eng. Sci. 1978, 33, 795-804) have shown that for a channel with rectangular cross-section of width W and depth d, longitudinal diffusivities can attain values as large as approximately 8 K0 for small values of the aspect ratio d/W, where K0 is the value of the longitudinal diffusivity obtained by ignoring all variations across the channel. Microchannels in lab-on-a-chip geometries are often not rectangular in cross-section. Isotropic etching techniques, for example, lead to channels with quarter-circular ends. In this paper we examine the effect of this geometry on the magnitude of longitudinal dispersivity for pressure-driven flows and also investigate modifications to this design which may minimize such dispersion. Optimal channel profiles are shown to lead to dispersivities approaching K0, the theoretical minimum, for small values of d/W.     

Bitterness reduction in grapefruit juice through active packaging

Naringin and limonin are the principle bitterness components of citrus juices. Our objective was to determine if the perceived bitterness in grapefruit juice could be reduced during storage through interaction with active packaging film. Storage of 10° Brix grapefruit juice at 7°C in contact with fungal-derived naringinase immobilized on cellulose acetate film reduced bitterness as perceived by a sensory panel. The films reduced naringin and limonin concentration by hydrolysis and adsorption respectively. Reduction in the naringin and limonin content of grapefruit juice by cellulose acetate films containing immobilized enzyme from 600–400 mg/l and 8.0–6.7 mg/l respectively could be detected as a reduction in bitterness by a sensory panel (p < 0.10). As the area of film (cm²)/volume of juice (ml) ratio increased from 1.1 to 3.6, the time to decrease the naringin level decreased. The reduction in naringin was not affected by agitation or holding the samples quiescently. The amount of enzyme desorbed from the film represented only 2% of the amount of enzyme immobilized in the film. The reduction in bitterness comes from direct interaction with the active packaging films. © 1998 John Wiley & Sons, Ltd.     

Flexible models for accidents on Chilean roads

The effect of both traffic flow and geometry on accidents is analyzed on the basis of a time series of a cross section of two-lane Chilean paved roads. Two linear specifications of functions explaining total accidents, accidents involving pedestrians (AIP) and the total less AIP, are compared against a flexible quadratic form. The results show that second order effects, particularly those of geometric characteristics, are highly significant; moreover, their omission causes a relevant downward bias on the marginal effect of flow on accidents. These results suggest that flexible forms are more appropriate for analyzing the contribution of flow and geometry to the level of accidents on a particular road section.     

Design space dimensionality reduction through physics-based geometry re-parameterization

The effective control of the extent of the design space is the sine qua non of successful geometry-based optimization. Generous bounds run the risk of including physically and/or geometrically nonsensical regions, where much search time may be wasted, while excessively strict bounds will often exclude potentially promising regions. A related ogre is the pernicious increase in the number of design variables, driven by a desire for geometry flexibility—this can, once again, make design search a prohibitively time-consuming exercise. Here we discuss an instance-based alternative, where the design space is defined in terms of a set of representative bases (design instances), which are then transformed, via a concise, parametric mapping into a new, generic geometry. We demonstrate this approach via the specific example of the design of supercritical wing sections. We construct the mapping on the generic template of the Kulfan class-shape function transformation and we show how patterns in the coefficients of this transformation can be exploited to capture, within the parametric mapping, some of the physics of the design problem.     

Accelerating crack growth simulations through adaptive model order reduction

Accurate numerical modeling of fracture in solids is a challenging undertaking that often involves the use of computationally demanding modeling frameworks. Model order reduction techniques can be used to alleviate the computational effort associated with these models. However, the traditional offline-online reduction approach is unsuitable for complex fracture phenomena due to their excessively large parameter spaces. In this work, we present a reduction framework for fracture simulations that leaves out the offline training phase and instead adaptively constructs reduced solutions spaces online. We apply the framework to the thick level set (TLS) method, a novel approach for modeling fracture able to model crack initiation, propagation, branching, and merging. The analysis starts with a fully-solved load step, after which two consecutive reduction operations—the proper orthogonal decomposition and the empirical cubature method—are performed. Numerical features specific to the TLS method are used to define an adaptive domain decomposition scheme that allows for three levels of model reduction coexisting on the same finite element mesh. Special solutions are proposed that allow the framework to deal with enriched nodes and a dynamic number of integration points. We demonstrate and assess the performance of the framework with a number of numerical examples.     

Assessment of weld reduction factors through experimental reference curves

The 2¼Cr1Mo (P22) is present in most of structural high-temperature applications, as results from a review on materials employed for the construction of both power and chemical plants. So, it fits well for an experimental activity in the laboratory as reference material. ISPESL, the Italian Certification Agency, carried out a low-budget program of creep and low-cycle fatigue (LCF) tests at 550 °C; the specimens (twelve plus two spare) of as-fabricated material came from a thick-wall pipe with a certified circumferential weld. They were base metal and cross-weld fusion-line centered ones. Comparison of the resistance curves obtained from LCF tests with those from codes (ASME and ISPESL) showed for the base metal good correspondence; therefore, showed the reliability of the test proceeding. For the weld it showed instead conservatism reduction at high-strain levels for the ASME design curve; moreover, it revealed an insufficient conservatism of the reduction factor proposed, which is 1/2, for the lower bound ISPESL curve. Comparison of the resistance curves obtained from creep tests with those from codes showed this: for both the base metal and weld there are a good correspondence and acceptable (low) conservatism of the strength reduction factor (SRF) proposed; for the load and temperature levels considered in the tests, it equals one. Still, the creep tests duration was within thirty hundred hours each; therefore the levels of the applied load (150.2-100 MPa) were not as low as those in typical operation conditions. For these cases, the code (ASME) proposes a lower-than-unity SRF: thus, longer tests (lower levels of the applied load) would be useful, also extending the activity to other materials.     

A laboratory investigation on bonding properties of dowels in concrete roads

Inclined dowel bars and unmovable bars may cause pavement cracking in the vicinity to the bar ends. The aim of the investigation is to study if there are any differences in bonding properties due to dowel material, coating or diameter of the dowel. Steel dowels with different coatings and dowels made of composite material are tested. The maximum draw-out force for a draw-out travel of 1.5 mm is measured. The test is repeated four times and ends with a final cycle to establish the constant force needed for a draw-out travel of 5 mm. Steel dowels with bituminous coating show the lowest initial draw-out force. The draw-out force increased 2 to 3 times with a diameter increase of 50% for steel dowels with plastic coatings. For composite dowels the comparing results showed an increase of draw-out force 2 to 5 times with an increase in diameter with one third. The results from the repeating test for several cycles showed that the draw-out and push-back force were almost the same for all dowels. However, for the dowels with bituminous coating a higher push-back force was needed compared to the draw-out force. It should be noted that the testing speed could affect the results, especially for dowels with bitumen.

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Résumé Des goujons d’assemblage inclinés ou inamovibles peuvent engendrer des fissures au voisinage de leur extrémité. L’objectif de cette étude est de déterminer si les propriétés d’adhésion dépendent du matériau utilisé pour le goujon, de son revêtement ou de son diamètre. Des goujons en acier avec différents revêtements ainsi que des goujons en matériau composite sont testés. La force maximale correspondant à une extraction de 1.5 mm est mesurée. Le test est répété quatre fois et est suivi d’un cycle final pour déterminer la force constante nécessaire à une extraction de 5 mm. La plus petite force initiale d’extraction est obtenue pour les goujons en acier avec un revêtement bitumineux. Pour les goujons en acier avec revêtement plastique, la force d’extraction augmente de deux à trois fois lorsque le diamètre augmente de 50%. Pour les goujons en composite, la force d’extraction augmente de deux à cinq fois lorsque le diamètre augmente d’un tiers. Les tests comportant plusieurs cycles ont montré que les forces d’extraction et de rétraction étaient pratiquement similaires pour tous les goujons. Cependant, pour les goujons avec revêtement bitumineux, la force de rétraction était supérieure à celle d’extraction. Il doit être noté que la vitesse avec laquelle les essais étaient réalisés pouvait affecter les résultats, particulièrement pour les goujons avec revêtement bitumineux.

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Editorial note The Swedish Cement and Concrete Research Institute (CBI) is a RILEM Titular Member.     

Investigation of pedestrian crashes on two-way two-lane rural roads in Ethiopia

Understanding pedestrian crash causes and contributing factors in developing countries is critically important as they account for about 55% of all traffic crashes. Not surprisingly, considerable attention in the literature has been paid to road traffic crash prediction models and methodologies in developing countries of late. Despite this interest, there are significant challenges confronting safety managers in developing countries. For example, in spite of the prominence of pedestrian crashes occurring on two-way two-lane rural roads, it has proven difficult to develop pedestrian crash prediction models due to a lack of both traffic and pedestrian exposure data. This general lack of available data has further hampered identification of pedestrian crash causes and subsequent estimation of pedestrian safety performance functions. The challenges are similar across developing nations, where little is known about the relationship between pedestrian crashes, traffic flow, and road environment variables on rural two-way roads, and where unique predictor variables may be needed to capture the unique crash risk circumstances. This paper describes pedestrian crash safety performance functions for two-way two-lane rural roads in Ethiopia as a function of traffic flow, pedestrian flows, and road geometry characteristics. In particular, random parameter negative binomial model was used to investigate pedestrian crashes. The models and their interpretations make important contributions to road crash analysis and prevention in developing countries. They also assist in the identification of the contributing factors to pedestrian crashes, with the intent to identify potential design and operational improvements.     

An observational study of driving distractions on urban roads in Spain

The present research investigated the prevalence of driver engagement in secondary tasks and whether there were any differences by age and gender, as well as day of the week and time of the day. Two independent researchers observed 6578 drivers at nine randomly selected urban locations in Girona, Spain. Nearly 20% of the drivers observed were engaged in some type of secondary task, with the most common being: conversing with a passenger (11.1%), smoking (3.7%) and talking on a handheld mobile phone (1.3%). Surprisingly there were no differences by gender, but there were age-related differences with younger drivers being more frequently observed engaged in a number of different types of secondary tasks while driving (i.e. drinking, talking on a handheld mobile phone, and texting or keying numbers). Logistic regression showed that younger drivers, and to a lesser extent middle-age drivers, were significantly more likely to be observed engaged in a technological distraction than older drivers. Conversely, non-technological distractions were significantly predicted by day of the week, time of the day and location. A substantial number of the drivers observed in this study were putting themselves at an increased risk of becoming involved in a crash by engaging in non-driving related tasks at the same time as driving. Furthermore, the higher crash rate among young drivers may be partially accounted for by their more frequent engagement in some types of secondary tasks while driving.     

Driving simulator for speed research on two-lane rural roads

The paper reports on a validation study of the interactive fixed-base driving simulator of Inter-University Research Center for Road Safety (CRISS) that was effectuated in order to verify the CRISS driving simulator's usefulness at a tool for speed research on two-lane rural roads. Speeds were recorded at eleven measurement sites with different alignment configurations on a two-lane rural road near Rome. The real world was reproduced in the CRISS driving simulator. Forty drivers drove the simulator. The results of the comparative and statistical analysis established the relative validity and also revealed that absolute validity was obtained in nine measurements sites. Only in two non-demanding configurations, were the speeds in simulator significantly higher than those recorded in the field. In these sites the mean speed in simulator was equal to or greater than 94 km/h. For these configurations, the higher speeds recorded in simulator appeared to stem from the different risk perception on the simulated road as opposed to that on the real road. The study's results should be considered for driving speed behavior research, in which simulator equipment with similar features of the CRISS driving simulator is used.     

Effects on road safety of new urban arterial roads

This paper presents an evaluation of the effects on road safety of new urban arterial roads in Oslo, Norway, and a synthesis of evidence from similar studies that have evaluated the safety effects of new urban arterial roads in other cities. A before-and-after study was made of four urban arterial road projects in Oslo. The study controlled for general accident trends in Oslo and for regression-to-the-mean. A statistically non-significant reduction of 9% in the number of injury accidents was found for all four projects combined. The effects on safety of new urban arterial roads were found to vary, depending on whether a new arterial road was built, or an existing arterial road upgraded by means of lane additions and reconstruction of junctions to interchanges. New arterial roads tend to induce more traffic, which tends to offset the benefits of a lower accident rate on the new roads. The results for other cities are very consistent with those for Oslo. For a total of seven cases in which new arterial roads were built, a statistically non-significant reduction of 1% in the number of injury accidents was found. Two cases that involved lane additions and converting at-grade junctions to interchanges resulted in a mean accident reduction of 51%, which was highly significant. On the average, the nine arterial road projects from which evidence was summarised resulted in a net induced traffic of 16%, and a net reduction in accident rate (accidents per million vehicle kilometres) of 18%. These effects almost cancel each other, leading to a very small net change in the expected number of accidents.     

Driving performance impairments due to hypovigilance on monotonous roads

Drivers’ ability to react to unpredictable events deteriorates when exposed to highly predictable and uneventful driving tasks. Highway design reduces the driving task mainly to a lane-keeping manoeuvre. Such a task is monotonous, providing little stimulation and this contributes to crashes due to inattention. Research has shown that driver’s hypovigilance can be assessed with EEG measurements and that driving performance is impaired during prolonged monotonous driving tasks. This paper aims to show that two dimensions of monotony – namely road design and road side variability – decrease vigilance and impair driving performance. This is the first study correlating hypovigilance and driver performance in varied monotonous conditions, particularly on a short time scale (a few seconds). We induced vigilance decrement as assessed with an EEG during a monotonous driving simulator experiment. Road monotony was varied through both road design and road side variability. The driver’s decrease in vigilance occurred due to both road design and road scenery monotony and almost independently of the driver’s sensation seeking level. Such impairment was also correlated to observable measurements from the driver, the car and the environment. During periods of hypovigilance, the driving performance impairment affected lane positioning, time to lane crossing, blink frequency, heart rate variability and non-specific electrodermal response rates. This work lays the foundation for the development of an in-vehicle device preventing hypovigilance crashes on monotonous roads.     

Safety impact of engineering treatments on undivided rural roads

This article presents an evaluation of the safety impacts of four engineering treatments implemented in the Autonomous Community of Madrid (Spain): highway upgrading; updating and improvement of traffic signing; repainting of pavement markings and pavement resurfacings. This evaluation was carried out using the Empirical Bayes method with a comparison group. The functioning of a methodology to test the significance of the safety impact is described. The results show that highway upgrading has a positive and significant safety impact, while the updating and improvement of traffic signing, the repainting of road markings and pavement resurfacings do not exhibit a significant impact on safety.     

Driving performance impairments due to hypovigilance on monotonous roads

Drivers' ability to react to unpredictable events deteriorates when exposed to highly predictable and uneventful driving tasks. Highway design reduces the driving task mainly to a lane-keeping manoeuvre. Such a task is monotonous, providing little stimulation and this contributes to crashes due to inattention. Research has shown that driver's hypovigilance can be assessed with EEG measurements and that driving performance is impaired during prolonged monotonous driving tasks. This paper aims to show that two dimensions of monotony - namely road design and road side variability - decrease vigilance and impair driving performance. This is the first study correlating hypovigilance and driver performance in varied monotonous conditions, particularly on a short time scale (a few seconds). We induced vigilance decrement as assessed with an EEG during a monotonous driving simulator experiment. Road monotony was varied through both road design and road side variability. The driver's decrease in vigilance occurred due to both road design and road scenery monotony and almost independently of the driver's sensation seeking level. Such impairment was also correlated to observable measurements from the driver, the car and the environment. During periods of hypovigilance, the driving performance impairment affected lane positioning, time to lane crossing, blink frequency, heart rate variability and non-specific electrodermal response rates. This work lays the foundation for the development of an in-vehicle device preventing hypovigilance crashes on monotonous roads.     

Full-field sensitivity analysis through dimension reduction and probabilistic surrogate models

Computational mechanics models often are compromised by uncertainty in their governing parameters, especially when the operating environment is incompletely known. Computational sensitivity analysis of a spatially distributed process to its governing parameters therefore is an essential, but often costly, step in uncertainty quantification. A sensitivity analysis method is described which features probabilistic surrogate models developed through equitable sampling of the parameter space, proper orthogonal decomposition (POD) for compact representations of the process’ variability from an ensemble of realizations, and cluster-weighted models of the joint probability density function of each POD coefficient and the governing parameters. Full-field sensitivities, i.e. sensitivities at every point in the computational grid, are computed by analytically differentiating the conditional expected value function of each POD coefficient and projecting the sensitivities onto the POD basis. Statistics of the full-field sensitivities are estimated by sampling the surrogate model throughout the parameter space. Major benefits of this method are: (1) the sensitivities are computed analytically and efficiently from regularized surrogate models, and (2) the conditional variances of the surrogate models may be used to estimate the statistical uncertainty in the sensitivities, which provides a basis for pursuing more data to improve the model. Synthetic examples and a physical example involving near-ground sound propagation through a refracting atmosphere are presented to illustrate the properties of the surrogate models and how full-field sensitivities and their uncertainties are computed.