Maximum Speed Reduction Research Articles

Effects of explosion-venting interlayer within utility tunnels on the characteristics of natural gas explosions

With the rapid expansion of the national economy and strategic adjustments to the energy structure, natural gas, a crucial clean energy source, encounters significant safety challenges during transportation in utility tunnels, owing to its flammable and explosive nature. To effectively address the current issues in response technologies for gas explosions in utility tunnels, such as inadequate control over the flame propagation range, limited attenuation of overpressure, and the mechanical impact damage effects on the internal structures of the utility tunnels and surrounding buildings, a small-scale experimental platform was constructed independently. This platform is designed to explore how the area and position of vents affect the characteristics of methane explosions within tunnels, utilizing the explosion venting mechanism. The results indicate that, for the same venting position, the maximum flame propagation distance, speed, and peak overpressure all decrease as the venting area increases. When the vent is located at position 1 in each compartment, the reduction in maximum flame propagation distance and speed is the most significant. The maximum decrease in peak overpressure occurs at venting position 2. When the venting position is closer to the ignition source, the rate of explosion overpressure rise and the explosion index both decrease with an increase in venting area, with the most significant reduction occurring at venting position 1. Conversely, when the venting position is farther from the ignition source, the rate of explosion overpressure rise and the explosion index actually increase, with the most significant increase occurring at venting position 4. The research findings offer a theoretical foundation and scientific guidance for developing new technologies aimed at mitigating gas explosion disasters in utility tunnels through internal venting.

Measuring Traffic Speed Change After the Reallocation of Road Space for Cycling: A Data-Driven Analysis for Bogotá

In recent years, many local authorities have sought to accommodate cycling and active transportation in urban areas by creating dedicated spaces for them. However, densely populated cities face a land shortage, making it challenging to introduce measures such as bike lanes without impacting existing road users. Therefore, understanding the potential impacts of these initiatives is essential for informed decision-making, effective policy formulation, and successful urban planning strategies. In 2020, Bogotá, Colombia introduced extensive bike lanes along important corridors previously exclusively designated for motorized vehicles. The modifications were made possible in response to the unique context of the COVID-19 pandemic. The objective of this study is to provide a data-driven assessment of the impacts of some of the implemented bike lanes by utilizing traffic speed data from 2019 (prior to the lane modifications) and 2021 (after the modifications). Rigorous statistical analysis and modeling were employed to measure the changes on speed levels of road traffic, on both, the treatment group with modified roads as well as on the control group with non-modified roads within the study area. Due to the intricate factors influencing traffic speeds, spatial relationships between road segments and estimation errors were explicitly accounted for. Findings revealed a maximum speed reduction of 4.5 km/h (equivalent to a 19 % decrease), for users on modified roads. Apart from quantifying the worsened speed conditions because of the reduced road space on treated segments, results also highlight that certain parallel road segments experienced an increase in speed levels. This observation lends support to the intervention and emphasizes the importance of comprehensively assessing the entire road network when considering the implementation of bike lane projects in similar context cities.

A speed loop control method of a laser tracing measurement control system

In a laser tracking control system, a motor drives the load to achieve continuous forward and reverse rotation speed control, and the magnitude of the load changes periodically during the motor rotation to realize tracking. Based on these characteristics, we propose an integral-separated improved variable universe fuzzy proportional-integral (PI) control method with torque feedforward compensation method in this study. The proposed method achieves the control performances of fast response, high steady-state accuracy, and strong anti-interference. The conventional fuzzy PI control method achieves good performance only in the unidirectional acceleration of a motor; therefore, we have improved its fuzzy rules, and designed a novel universe contraction–expansion factor. Additionally, a load torque observer is introduced to observe and compensate for the external load and to further improve the anti-interference performance of the tracking control system. The experimental results demonstrate that the integral-separated improved variable-universe fuzzy PI control method achieves better performance in the forward and reverse speed regulation processes of the motor. The overshoot is 92% less than that of the conventional PI control when the target speed is set to ±500 rpm. The Luenberger observer is introduced to observe and compensate for the load torque. After the stabilizing the speed and applying an external load of 0.2 N m to the motor, the maximum speed reduction is observed to be 59% less than that obtained using the conventional PI control. The improved PI control method satisfies the speed loop control requirements of the laser tracking control system and can improve the steady-state tracking accuracy and robustness of the system.

Using multicolor perceptual markings as a rear-end crash risk mitigator: A field investigation

Perceptual markings on roadways are prevailing countermeasures with substantial effectiveness for accident prevention, and a variety of alternatives and derivatives of them are developed to expect to receive an augmented performance of behavioral intervention and crash risk mitigation. However, the proper use of colors as a way of developing effective and innovative perceptual markings is seldomly recognized in-depth from the perspective of visual perceptual mechanism in behind. Given this, in this study, we introduced a kind of multicolor perceptual markings (MCPMs) pattern, i.e., one red marking follows one yellow marking (“1Y + 1R”), two red markings follow two yellow markings (“2Y + 2R”), and three red markings follow three yellow markings (“3Y + 3R”), and evaluated their effects on longitudinal and lateral driving behaviors and real-time safety benefits in car-following via a series of field investigation on a real-world expressway in China. The statistical analyses of the relative differences of speed (θv), distance headway (θd), time headway (θh), lateral movement (θp), and crash risk (ηmTTC and ηDRAC, developed from time-to-collision (TTC) and deceleration rate to avoid crash (DRAC)) suggest that, 1) the MCPMs could lead to substantial increases in car-following time and distance headways, and reduction in speed. The maximum time headway increase (0.61 s), speed reduction (1.42 m/s), and distance increase (3.6 m) were found in the condition of “1Y + 1R” compared with the baseline; 2) the MCPMs stabilized the lateral movement of vehicles on the lane at each observation section, and “1Y + 1R” yielded the best performance of lane-keeping; 3) the MCPMs yielded applaudable real-time safety benefits, which were believed to afford the drivers a better chance to accommodate their behaviors to a safer car-following status. The findings of this study suggest the MCPMs could be an especially applaudable form of perceptual markings, and could also be a critical reference of how to use colors in a better way for developing augmented perceptual markings.

Assessment of Permeability Windbreak Forests with Different Porosities Based on Laser Scanning and Computational Fluid Dynamics

Accurate modeling of windbreaks is essential for the precise assessment of wind protection performance. However, in most windbreak studies, the models used the approximate shape of the simulated trees, resulting in significant differences between the simulated results and the actual situation. In this study, terrestrial laser scanning (TLS) was used to extract tree parameters, which were used in a quantitative structural model (AdQSM) to recreate the tree structure and restore the wind field environment using the computational fluid dynamics software PHOENICS. In addition, we compared the bias, precision, and accuracy of porosity of Ginkgo biloba (with elliptical crown) and Populus alba (with conical crown), which have been commonly used in previous windbreak studies. The results showed that AdQSM has a high reduction rate and ability to reproduce the field conditions of the study area. After wind field simulation, the wind speed root mean square errors of the point cloud model at three heights (3, 6, and 9 m) were 0.272, 0.377, and 0.437 m/s, respectively, and the wind speed correlation coefficients r were 0.967, 0.965, and 0.937, respectively, which were significantly more accurate than those of the remaining two structures. Finally, the porosity of the windbreak forest obtained using the modeled sample plot showed a higher correlation with the wind permeability coefficient than that obtained using the existing approach. Windbreak models with three different porosities under the same conditions had different effects on the wind environment, particularly the location of the maximum wind speed reduction, variation of wind speed with porosity, and recovery rate of leeward wind speed. TLS can accurately extract windbreak factors and calculate the porosity, thus greatly improving the reliability of windbreak effect research in windbreak forests. This study provides a promising direction for future research related to the simulation of windbreak effects in windbreak forests.

Optical pavement treatments and their impact on speed and lateral position at transition zones: A driving simulator study

Transition zones are a road section where posted speed drops from higher to lower limits. Due to the sudden changes in posted speed limits and road environment, drivers usually do not adapt to the posted speed limits and underestimate their traveling speed. Previous studies have highlighted that crash rates are usually higher in these sections. This study aims at improving the safety at transition zones by introducing perceptual measures that are tested using a driving simulator. The proposed measures are speed limit pavement markings with a gradual increase of brightness and/or size that were placed at transition zones in simulation scenarios replicating the real-world environment of the Doha Expressway in Qatar. These innovative measures aim to produce the impression of increased speed that could stimulate drivers to better adapt speed limits. The driving behavior of 81 drivers possessing a valid Qatari driving license was recorded with a driving simulator interfaced with STISIM Drive® 3. Results showed that pavement markings combining size and brightness manipulations were the most effective treatment, keeping drivers' traveling speed significantly below the traveling speed recorded in the untreated control condition. In this regard, the maximum mean speed reductions of 5.3 km/h and 4.6 km/h were observed for this treatment at the first transition (120 to 100 km/h) and second transition (100 to 80 km/h) zones, respectively. Regarding the variations in drivers' lateral position, the results showed that the proposed pavement markings did not negatively influence drivers' lateral control on the road as the maximum observed standard deviation of lateral position was around 0.065 m. This study shows that the proposed pavement markings are recommended for improving the speed adaptation of drivers in the transition zones.

Impacts of blade inlet angle of diffuser on the performance of a submersible pump

A diffuser acts as an energy conversion device to improve the performance of a submersible pump. The blade inlet angle of a diffuser is the most important geometric parameter that affects the performance of a submersible pump. The present paper focused on the effects of different blade inlet angles of a diffuser on the performance of a submersible pump. Firstly, the theoretical analysis of the diffuser characteristic curve was carried out; Secondly, five sets of submersible pump models with different blade inlet angles and the same impeller were built and simulated. Finally, based on the obtained results, two characteristic parameters reflecting inlet and outlet velocity distributions in the diffuser were introduced, and the quantitative relationship between internal and external characteristics of the diffuser was established. It was found that as the blade inlet angle of the diffuser increased, the optimum operating point moved in the direction of large flow rate. When the blade inlet angle of the diffuser was in the range of 27°–30°, the efficiency of the submersible pump reached more than 75%, and the maximum change in the corresponding working flow was 0.2 times of the theoretical discharge. Furthermore, the values of the maximum speed reduction ratio ([Formula: see text], that is the ratio of inlet circumferential flow velocity to minimum flow velocity on the intermediate flow surface of a diffuser.) were located near 1.6, and they were positioned ([Formula: see text], that is the relative position of the lowest flow velocity on the intermediate flow surface along the flow path of the diffuser.) near the midpoint of the flow path of the diffuser. Moreover, with the increase in the change rate of different blade inlet angles ([Formula: see text]), the high-efficiency interval breadth ([Formula: see text], that is the relative rate of change in flow rate with respect to the highest flow rate at [Formula: see text].) manifested an increasing trend. When [Formula: see text] exceeded 0.06, the value of [Formula: see text] increased significantly, and the range of applicable flow intervals expanded simultaneously. According to performance requirements, the distribution of the internal flow field was specified to further enhance the adaptability of the submersible pump to different working conditions.

Speed humps and speed tables: Externalities on vehicle speed, pollutant emissions and fuel consumption

Abstract Speed hump/table are devices used on roadways with the objective of reducing vehicular speed. Nevertheless, the effects of said devices on traffic streams are not that clear. Therefore, through descriptive statistics and approximations of linear models, an analysis was carried out on a collector street, as a case of study, taking into consideration the shapes and spacing of bumps, and pollution and fuel consumption of vehicles. The results indicate that the shape and size of the speed control devices are the most important factors for efficiency in reducing maximum speed between devices, achieving a reduction of 50%–75% with speed humps, and a 10%–65% reduction of maximum speed in those which are trapezoidal shape (speed tables). The spacing between speed control devices does not significantly effect a vehicles speed upon passing over said devices, but it does have an impact on pollutant vehicle emissions and extra gasoline consumption. The estimated models to calculate the speed control device characteristics can help to determine which geometric shapes to use when deciding about type and placement of the device, depending on the requirements of a particular thoroughfare.

A Numerical Study of Aerosol Effects on Electrification with Different Intensity Thunderclouds

Numerical simulations are performed to investigate the effect of varying CCN (cloud condensation nuclei) concentration on dynamic, microphysics, electrification, and charge structure in weak, moderate, and severe thunderstorms. The results show that the response of electrification to the increase of CCN concentration is a nonlinear relationship in different types of thunderclouds. The increase in CCN concentration leads to a significant enhancement of updraft in the weak thunderclouds, while the high CCN concentration in moderate and severe thunderclouds leads to a slight reduction in maximum updraft speed. The increase of the convection promotes the lift of more small cloud droplets, which leads to a faster and stronger production of ice crystals. The production of graupel is insensitive to the CCN concentration. The content of graupel increases from low CCN concentration to moderate CCN concentration, and slightly decreases at high CCN concentration, which arises from the profound enhancement of small ice crystals production. When the intensity of thundercloud increases, the reduction of graupel production will arise in advance as the CCN concentration increases. Charge production tends to increase as the aerosol concentration rises from low to high in weak and moderate thundercloud cases. However, the magnitude of charging rates in the severe thundercloud cases keeps roughly stable under the high CCN concentration condition, which can be attributed to the profound reduction of graupel content. The charge structure in the weak thundercloud at low CCN concentrations keeps as a dipole, while the weak thunderclouds in the other cases (the CCN concentration above 100 cm−3) change from a dipole charge structure to a tripole charge structure, and finally disappear with a dipole. In cases of moderate and severe intensity thunderclouds, the charge structure depicts a relatively complex structure that includes a multilayer charge region.

Effect of Horizontal Curve Geometry on the Maximum Speed Reduction: A Driving Simulator-Based Study

Operating speed reduction models can be used to evaluate the geometric design consistency. The proposed study developed a maximum speed reduction model for drivers habituated in weak lane disciplined driving conditions. The required experiment was carried out on a fixed-base driving simulator. The speed profiles of 48 participating drivers along 24 different tangent-curve configurations were recorded. The maximum speed at the preceding tangent and the minimum speed in the following curve were used to estimate the maximum speed reduction (MSR) of each subject driver. A multiple regression model was developed for the obtained 85th percentile maximum speed reduction data and the road geometric parameters such as radius, curvature, preceding tangent length, curve length, gradient, shoulder width, and extra-widening. The developed model identified curvature (i.e., the inverse of radius) and preceding tangent length as predictor variables. Based on the obtained results, a nomogram for road geometric safety evaluation is proposed in the paper.

Decrease of the Maximum Speed in Highway Tunnels as a Measure to Foster Energy Savings and Sustainability

The high energy consumption of the lighting installations in highway tunnels has become a hot topic in the last few years due to the high figures in terms of money, consumed energy, use of raw materials, emissions of greenhouse gases due to the remarkable number of manufactured elements, and maintenance, among others. In spite of the different strategies proposed up to date and their savings, the potential benefits of decreasing the maximum speed allowed in tunnels have not been considered in depth as a complementary measure yet. In this work, the impact of such a decrease in terms of energy consumption, number projectors, carbon dioxide (CO2) emissions, and yearly costs in energy is analyzed and discussed. The results strongly suggest the convenience of introducing maximum speed reduction in traffic regulations which, in addition, could create positive synergies with traffic safety.

DOXORUBICIN-INDUSED DISTURBANCES OF CARDIOMYOCYTE CONTRACTILE ACTIVITY.

The aim of our study was to find out the mechanisms of cardiomyocyte contractile activity disturbances under the influence of anthracycline antibiotics and curcumin correction capabilities, to clarify the role of the mitochondrial membrane potential changes in cardiomyocyte contractile activity. It was investigated disturbances of contractile activity of the rat neonatal cardiomyocytes under the influence of anthracycline antibiotics (doxorubicin), and the possibility of correcting these violations using antioxidant curcumin. In addition, there was researched the role of mitochondrial membrane potential changes in reducing contractile activity of the cardiomyocytes. We established that doxorubicin causes significant changes in all reduction parameters compared to control: increased frequency of spontaneous contractions, violation of rhythm, lower amplitude and the shortening %, increase in the maximum speed of contraction and relaxation without changes in duration of these processes. Compatible incubation with doxorubicin and curcumin caused a consid- erable decrease of the incidence of spontaneous emission (3 times), restored their rhythm, increasing the amplitude of 2 times and the shortening % (8,15 ± 0,37), rising the maximum speed reduction to 1,8 times and the relaxation speed of 16 %, with no significant change in duration of these processes compared to monoincubation with doxorubicin. In the fluorescence study of neonatal cardiomyocytes mitochondrial potential was detected a significant reduction in mitochondria color brightness under the influence of doxorubicin - in 1,7 times compared to control. A compatible incubation of cells with curcumin and doxorubicin resulted in an elevation of mitochondria fluorescence (2,2 times compared to using of doxorubicin only).

Coordination of horizontal and sag vertical curves on two-lane rural roads: Driving simulator study

The highway geometric design guidelines for several countries provide suggestions for the coordination of horizontal curves overlapping with sag vertical curves (sag combinations) to avoid combined configurations that produce undesirable optical effects and reduced safety. Such suggestions are derived from studies based on the drawing of the perspective of the road. This drawing method is severely limited with respect to the simulation of the perspective view of the highway to the driver during the dynamic task of driving. Interactive driving simulation methods are deemed to be more efficient for these objectives.This paper reports the results of a study carried out using an interactive driving simulator to evaluate the effects on the driver's speed behavior of different configurations of sag combinations and non-combined curves on a flat grade with the same features as the horizontal curves of the sag combinations (reference curves). The speed behaviors of drivers along the tangent–curve transitions of sag combinations and reference curves were recorded. The speed on the approach tangent, the speed at the midpoint of the horizontal curve and the maximum speed reduction (MSR), the difference between the maximum speed on the last 200m of the approach tangent and the minimum speed on the first half of the horizontal curve, were analyzed. One-way repeated MANOVA was performed to determine if the driver's speed behavior on the horizontal curves was influenced by different configurations of sag combinations and reference curves.The primary result was that on suggested sag combinations, the driver's speed behavior did not differ in any statistically significant way from that on the reference curves. Whereas the critical sag combinations (configurations that should be avoided) caused high values of maximum speed reduction along the tangent–curve transition, which pointed to the driver's reaction to an incorrect perception of the road alignment. Therefore, this result confirmed the effectiveness of the road design guidelines for the coordination of horizontal curves and sag vertical curves.

Analysis of driver speeds under night driving conditions using a driving simulator

ProblemAccident statistics demonstrate that there should be a greater focus on nighttime driving to improve our knowledge of driver behavior under poor lighting conditions. However, the current geometric design criteria do not take into account driving at night. Moreover, studies that propose predictive models of operating speed only consider daytime driving conditions. MethodThis study compares driver speed behavior during daytime and nighttime driving and models operating speeds and speed differentials, identifying significant factors that influence speed behavior under different lighting conditions. The research was carried out using a driving simulator for a section of an existing two-lane rural road composed of 39 tangent–curve configurations. Speed profiles were recorded for 40 drivers under simulated daytime and nighttime driving conditions. ResultsNew predictive speed models, differentiated for daytime and nighttime driving, are proposed that highlight the effects of different geometric predictors under different visibility conditions. Specifically, predictive models for operating speed on curves identified the inverse of the radius and the deflection angle of the curve as predictors under both driving conditions. For speed differentials based on the 85th percentile for maximum speed reduction (85MSR), we found that the inverse of the approaching tangent length and of the curve radius significantly explained the dependent variable in both cases, with a higher dependence of nighttime 85MSR on the curve geometry than on the tangent length. Tangent length had a significant effect on operating speed for independent tangents only for the daytime model, whereas the inverse of the previous radius was confirmed as a predictor for both visibility conditions. Practical applicationsThis research may influence design considerations for nighttime driving by providing evidence of the effects of nighttime conditions on driver speed choices and road safety.

Prediction of Drivers’ Speed Behavior on Rural Motorways Based on an Instrumented Vehicle Study

Several studies have developed operating speed prediction models. Most of the models are based on spot speed data, collected by radar guns, pavement sensors, and similar mechanisms. Unfortunately, these data collection methods force the users to assume some invalid assumptions in driver behavior modeling: constant operating speed throughout horizontal curves and occurrence of acceleration and deceleration only on tangents. In this study, an instrumented vehicle with GPS continuous speed tracking was used to analyze driver behavior in terms of speed choice and deceleration or acceleration performance and to develop operating speed prediction models. The data used in the study were from a field experiment conducted in Italy on the rural motorway A16 (Naples–Avellino). Models were developed to predict operating speed in curves and tangents, deceleration and acceleration rates to be used in the operating speed profiles, starting and ending points of constant operating speed in a curve, 85th percentile of the deceleration and acceleration rates of individual drivers, and 85th percentile of the individual drivers’ maximum speed reduction in the tangent-to-curve transition. The study results showed that (a) the drivers’ speed was not constant along curves, (b) the individual drivers’ maximum speed reduction was greater than the operating speed difference in the tangent-to-curve transition, and (c) the deceleration and acceleration rates experienced by individual drivers were greater than the deceleration and acceleration rates used to draw operating speed profiles.

KARAKTERISTIK POMPA SENTRIFUGAL ALIRAN CAMPUR DENGAN VARIABLE FREQUENCY DRIVE

In an industry that uses large centrifugal pumps continuously, pump speed setting can reduce energy consumption significantly. By changing the speed of a centrifugal pump, capacity, head, and pump power required will change according to pump affinity laws. Speed of a centrifugal pump can be changed by variable frequency drive . This study aimed to investigate the characteristics of mixed flow centrifugal pumps with variable frequency drive. The results showed that 10% of maximum speed reduction can decrease power consumtion until 50%, while the increase in the efficiency is maximum 7.2%. The power reduction is different for different speed reduction. In a dynamic head dominated system the efficiency will remain constant during speed reduction while in static head dominated system will change.

Relationship between Predicted Speed Reduction on Horizontal Curves and Safety on Two-Lane Rural Roads in Spain

According to different studies, speed reduction is considered one of the major factors in contributing road safety. For that reason, several guidelines have been recommended for maximum desirable speed reductions from tangents to horizontal curves and for maximum differentials between design and operating speeds on horizontal curves. The Interactive Highway Safety Design Model (IHSDM) Design Consistency Module presents an analysis of the relationship between speed reduction and crashes for horizontal curves on U.S. two-lane rural highways. This paper presents the relationship between speed reduction and crashes for horizontal curves on Spanish two-lane rural roads. A model for using regression analysis to predict crashes is presented. Exposure, curve length (CL), and difference in 85th-percentile speeds (ΔV85) between successive tangents and horizontal curves, as well as between successive curves, are used. The model's coefficients were different from the ones obtained for U.S. highways, although the values of the goodness-of-fit criteria were similar. In addition, the relationship between crashes and different speeds is analyzed, taking the difference in speed as a speed differential not exceeded by 85% of the drivers traveling under free-flow conditions (Δ85V), instead of considering it as ΔV85. The two models (ΔV85 versus Δ85V) give very similar results. Language: en

Effects of Simulated Day and Night Driving on the Speed Differential in Tangent–Curve Transition: A Pilot Study Using Driving Simulator

Objective: The pilot study described in this article aimed to analyze the driver speed profile for evaluation of road design consistency during simulated day and nighttime driving. The research, carried out using a driving simulator, was developed with the overall objectives of evaluating the speed differential during simulated nighttime driving for the identification of critical road situations not detected by design consistency evaluation during simulated daytime driving. Methods: An existing 2-lane rural road, where high accident rates were recorded during nighttime, was implemented in the driving simulator of the Inter-University Research Centre of Road Safety (CRISS) and the drivers’ speed profiles were recorded in both simulated day and nighttime driving conditions over the 39 tangent–curve configurations that composed the road alignment. Results: The analysis of the speed differential based on the 85MSR (Maximum Speed Reduction) indicator during simulated daytime driving was not able to identify critical road situations that the same analysis revealed during the simulated nighttime driving. Such results occurred for most of the tangent–curve configurations. Conclusions: The study demonstrated that limiting the speed analysis only to daytime driving conditions cannot exclude the possibility that during nighttime driving some road configurations could become unsafe. The findings of the study highlight the need to carry out design consistency evaluations for nighttime driving conditions.

Multifunzionalità e conflittualità nelle Zone 30

In the field of mobility, conflicts and local opposition may be generated not only by hard implementation of big transport infrastructures, but also by soft measures of traffic regulation. An example is represented by 20 mph Zones, which aim to enhance the intrinsic multifunctionality of urban streets: they try to limit the entity and the speed of car flows in residential areas through re-designing road spaces, so to improve in the meantime the liveableness and the environmental and aesthetic quality of these areas. The speed limitation of 20 mph can however determine protests and disputes by local residents and workers, as it disadvantages private motorized mobility, which represents – at least in most current Italian cities – the main form of mobility. The paper analyzes this kind of conflicts, through the case study of the Mirafiori Nord 20 mph Zone in Turin, which is recognized as a best practice in the Italian context. The analysis of this case, as well as the investigation of the main European and American guidelines on traffic calming techniques and plans, shows that a few critical issues turn out to be crucial in order to prevent and manage these conflicts. First of all, a prompt, well-timed communication plan is essential in order to inform residents and users of the area about the potential costs and benefits of traffic calming measures: even before implementation works begin, people has to know that lower accessibility levels by car will be compensated by an improvement of streets liveableness and environmental quality. From this perspective, residents should be involved in designing the new green and street equipments that may be placed, thanks to the redistribution of significant portions of road space to slow mobility components. Participation of school children is quite recommended, for example in the ideation of vertical signs for the access doors of the zone, in experiencing new pedestrian or cycling home-school journeys, and so on. Parking restrictions are often firmly unaccepted by residents, and should carefully assessed before being proposed. Regular reporting of monitored outcomes of the implemented traffic calming measures (mainly in terms of reduction of maximum speed, of dead or injured persons in road accidents, of pollution and noise local levels etc.) must allow keeping residents conscious of the actual benefits they can enjoy. Last, the implementation of 20 mph Zones must be framed in a more general strategy for urban mobility: push measures (just such as 20 mph Zones) for limiting accessibility levels to private traffic flows have to be counterbalanced by pull measures aimed at potentiating public transport, in order to better balance the modal split; otherwise, congestion on the primary road network could spread consistent traffic flows also inside residential areas, invalidating main benefits of traffic calming measures.

Mechanical strengths of molten and solidified LLDPE/LDPE blends and wood/LDPE composites under tensile deformation

AbstractThe mechanical strengths of neat low‐density polyethylene (LDPE), a blend of LDPE with linear low‐density polyethylene (LLDPE), and a composite of LDPE with wood flour (wood/LDPE) were investigated in molten and solidified states under tensile deformation. The results are discussed in terms of the effects of LLDPE and wood contents, roller speed, and volumetric flow rate. In LLDPE/LDPE blends, incorporating LLDPE from 0 to 30 wt% into LDPE caused a slight increase in drawdown force, a larger fluctuation in drawdown force, and a reduction of maximum roller speed to failure. The mechanical properties of the solidified LLDPE/LDPE corresponded to those of the molten LLDPE/LDPE with regard to the effect of LLDPE content. For wood/LDPE composites, increasing the wood flour content in molten LDPE caused considerable reductions in drawdown time and maximum roller speed to failure. The drawdown force increased with increasing wood flour up to 10 wt% before it decreased at the wood loading of 20 wt%. A number of voids and pores on the extrudate surfaces became obvious for the composites with 20 wt% of wood content. Increasing wood content enhanced the tensile modulus for the solidified LDPE but decreased its tensile strength. Unlike those of LLDPE/LDPE blends, the changes in tensile modulus and strength of solidified wood/LDPE composites with wood content did not correspond to those of the molten composites. In all cases, the drawdown force increased with increasing roller speed. The effect of volumetric flow rate from the extruder on the mechanical strengths of the solidified blends was more pronounced than on those of the molten ones. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers