Increase In Mean Speed Research Articles

Multi-Trip Time-Dependent Vehicle Routing Problem with Soft Time Windows and Overtime Constraints

The multi-trip time-dependent vehicle routing problem with soft time windows and overtime constraints (MT-TDVRPSTW-OT) is considered in this paper. The modified hierarchical multi-objective formulation and the equivalent single-objective formulation are proposed. The iterative multi-trip tour construction and improvement (IMTTCI) procedure and the single-trip tour counterpart procedure with post-processing greedy heuristic (ISTTCI-GH) are proposed to solve the problem. These procedures are based on the ruin and recreate principle, and consider trade-offs among cost components (vehicle usage, number of early/late soft time window occurrences, transport distance, transport time, overtime and early/late soft time window penalty costs) in the search process. From the computational experiment, the IMTTCI procedure outperforms the existing efficient insertion heuristic with 42.09% improvement in number of vehicles and 24.30% improvement in travel time for the constant-speed multi-trip vehicle routing problem with hard time windows and shift time limits, a special case of MT-TDVRPSTW-OT problem, on all problem instances. For the MT-TDVRPSTW-OT problem, the ISTTCI-GH and the IMTTCI outperform the ISTTCI on all problem groups by 43.21% and 69.44% in the number of vehicles (the primary objective), respectively. The IMTTCI outperforms the ISTTCI-GH in number of vehicles by 51.07%, but takes 42.83% longer CPU time than the ISTTCI-GH. The performance of IMTTCI in terms of the primary objective improves with the increase of mean speed as well as the increase of time window width and planning horizon across all customer configuration types, tighter/looser time windows, shorter/longer planning horizon and various time-dependent travel speed profiles. The sensitivity analysis of different problem parameters is performed. The complexity analysis of the proposed procedures shows that the proposed procedures are solvable in polynomial time, and from the computational results the relationships between the CPU time and problem size confirm this. For the MT-VRPSTW-OT, a mixed integer program and the special case of MT-TDVRPSTW-OT, on 12-customer instances, the proposed IMTTCI algorithm yields the average optimality gap of 1.35% with the average CPU time of 0.66 seconds, whereas the GAMS/CPLEX solver yields the average optimality gap of 0.83% with the average CPU time of 256.39 seconds. The proposed IMTTCI algorithm yields only 0.52% greater optimality gap but 388 times faster CPU time than the commercial solver.

High-speed container transport system

Background: The new scope of application for vehicles equipped with magnetic suspension is the fright container transportation. In order to realize the transit potential of the country, the increase in mean speed of the container trains is required.
 Aim: The present work aims to explore the possibilities to develop the high-speed transport system equipped with magnetic suspension for container transportation along Euro-Asian land bridge.
 Methods: As the research tools used methods of situational analysis, computer modeling, transport geography, technical and economic analysis.
 Results: The market analysis results of the transit container transportation have shown that the major challenge for Russian transit development is the constrained traffic capacity of the existing transport corridors. The drastic solution to the problem can be the construction of a new high-speed transport system. The following factors determining the conditions for the creation of the new transport system have been identified: use of transport possibilities of the Azov-Black Sea basin; ensuring accessibility of the northern territories; development of technical solutions for the creation of a transport system with low-cost infrastructure. The combined traction levitation system has been developed based on the extremely simple design of the linear switched reluctance motor. The experimental researches of the full-functional physical model of the transport platform have been performed. The assessment of investment project efficiency has shown that despite the large start-up investment in the track infrastructure, the project has positive economic effect.
 Practical importance: The computer model of the combined traction levitation system based on the linear switched reluctance motor has been designed. The concept of constructing a new transport system is proposed, taking into account the characteristics of the proposed operational region in poorly developed territories. The high-speed route has been proposed connecting the Azov-Black sea basin with the Pacific coastline and completely passing through the territories of Russia including some northern regions. The transit potential assessment has shown that due to the transit time reduction it is possible to attract the container freights with traffic volume of 1,52 million in twenty-foot equivalentunit.

Changes in the saltation flux following a step‐change in macro‐roughness

AbstractThe effect of a step change in macro‐roughness on the saltation process under sediment supply limited conditions was examined in the atmospheric boundary layer. For an array of roughness elements of roughness density λ = 0.045 (λ = total element frontal area/total surface area of the array) the horizontal saltation flux was reduced by 90% (±7%) at a distance of ≈150 roughness element heights into the array. This matches the value predicted using an empirical design model and provides confidence that it can be effectively used to engineer roughness arrays to meet sand flux reduction targets. Measurements of the saltation flux characteristics in the vertical dimension, including: saltation layer decay (e‐folding) height and particle size, revealed that with increasing distance into the array, the rate of mass flux change with increasing height decreased notably, and (geometric) mean particle diameter decreased. The distribution of the saltation mass flux in the vertical remains exponential in form with increasing distance into the roughness array, and the e‐folding height increases as well as increasing at a greater rate as particle diameter diminishes. The increase in e‐folding height suggests the height of saltating particles is increasing along with their mean speed. This apparent increase in mean speed is likely due to the preferential removal, or sequestration, of the slower moving particles across the size spectrum, as they travel through the roughness array. Copyright © 2018 John Wiley & Sons, Ltd.

Speed, speed variation and crash relationships for urban arterials

Speed and speed variation are closely associated with traffic safety. There is, however, a dearth of research on this subject for the case of urban arterials in general, and in the context of developing nations. In downtown Shanghai, the traffic conditions in each direction are very different by time of day, and speed characteristics during peak hours are also greatly different from those during off-peak hours. Considering that traffic demand changes with time and in different directions, arterials in this study were divided into one-way segments by the direction of flow, and time of day was differentiated and controlled for. In terms of data collection, traditional fixed-based methods have been widely used in previous studies, but they fail to capture the spatio-temporal distributions of speed along a road. A new approach is introduced to estimate speed variation by integrating spatio-temporal speed fluctuation of a single vehicle with speed differences between vehicles using taxi-based high frequency GPS data. With this approach, this paper aims to comprehensively establish a relationship between mean speed, speed variation and traffic crashes for the purpose of formulating effective speed management measures, specifically using an urban dataset. From a total of 234 one-way road segments from eight arterials in Shanghai, mean speed, speed variation, geometric design features, traffic volume, and crash data were collected. Because the safety effects of mean speed and speed variation may vary at different segment lengths, arterials with similar signal spacing density were grouped together. To account for potential correlations among these segments, a hierarchical Poisson log-normal model with random effects was developed. Results show that a 1% increase in mean speed on urban arterials was associated with a 0.7% increase in total crashes, and larger speed variation was also associated with increased crash frequency.

Altering the Speed Profiles of Wheelchair Rugby Players With Game-Simulation Drill Design.

To examine the speed profiles of elite wheelchair rugby (WCR) players during game-simulation training drills of differing player number and shot-clock regulations. A secondary aim was to determine whether the profiles were further influenced by player classification. Eight elite WCR players (low-point n = 3, high-point n = 5) were monitored using a radio-frequency-based indoor tracking system during training sessions over a 5-mo period. Speed profiles were collected for 3 modified game-simulation drills-3-versus-3 drills (n = 8 observations), 30-s shot clock (n = 24 observations), and 15-s shot clock (n = 16 observations)-and were compared with regular game-simulation drills (4 vs 4, 40-s shot clock; n = 16 observations). Measures included mean and peak speed; exercise-intensity ratios, defined as the ratio of time spent performing at high and low speeds; and the number of high-speed activities performed. Compared with regular game-simulation drills, 3-versus-3 drills elicited a moderate increase in mean speed (6.3%; effect size [ES] = 0.7) and the number of high-speed activities performed (44.1%; ES = 1.1). Minimal changes in speed profiles were observed during the 30-s shot clock, although moderate to large increases in all measures were observed during the 15-s shot-clock drills. Classification-specific differences were further identified, with increased activity observed for high-point players during the 3-versus-3 drill and for low-point players during the 15-s shot clock. By reducing the number of players on court and the shot clock to 15s, coaches can significantly increase elite WCR players' speed profiles during game-simulation drills.

Prerequisites for the Creation of a High-Speed Container Transport System

The new scope of application for vehicles equipped with magnetic suspension is the fright container transportation. In order to realise the transit potential of the country, the increase in mean speed of the container trains is required. Objective. The purpose of the work is to explore the possibilities to develop the highspeed transport system equipped with magnetic suspension for container transportation along Eurasian land bridge. Methods. The following methods and analysis have been used as research instruments: case study, computer modeling, transport geography and technical and economic analysis. Results. The market analysis results of the transit container transportation have shown that the major challenge for Russian transit development is the constrained traffic capacity of the existing transport corridors. The drastic solution of the problem can be the construction of a new high-speed transport system. The following factors determining the conditions for the creation of the new transport system have been identified: the use of the Azov-Black sea basin transportation facilities, provision of the accessibility of the northern areas; the development of technical solutions ensuring the design of the transport system with low cost infrastructure. The combined traction levitation system has been developed based on the extremely simple design of the linear switched reluctance motor. The experimental researches of the full-functional physical model of the transport platform have been performed. The assessment of investment project efficiency has shown that despite large start-up investment in the track infrastructure, the project has positive economic effect. Practical importance. The computer model of the combined traction levitation system based on the linear switched reluctance motor has been designed. The concept of the new transport system construction has been introduced taking into account the characteristics of the supposed operating test sites in poorly developed areas. The high-speed route has been proposed connecting the Azov-Black sea basin with the Pacific coastline and completely passing through the territories of Russia including some northern regions. The transit potential assessment has shown that due to the transit time reduction it is possible to attract the container freights with traffic volume of 1.52 million in twenty-pounds equivalent.

Raising the speed limit from 75 to 80 mph on Utah rural interstates: Effects on vehicle speeds and speed variance

IntroductionIn November 2010 and October 2013, Utah increased speed limits on sections of rural interstates from 75 to 80mph. Effects on vehicle speeds and speed variance were examined. MethodsSpeeds were measured in May 2010 and May 2014 within the new 80mph zones, and at a nearby spillover site and at more distant control sites where speed limits remained 75mph. Log-linear regression models estimated percentage changes in speed variance and mean speeds for passenger vehicles and large trucks associated with the speed limit increase. Logistic regression models estimated effects on the probability of passenger vehicles exceeding 80, 85, or 90mph and large trucks exceeding 80mph. ResultsWithin the 80mph zones and at the spillover location in 2014, mean passenger vehicle speeds were significantly higher (4.1% and 3.5%, respectively), as were the probabilities that passenger vehicles exceeded 80mph (122.3% and 88.5%, respectively), than would have been expected without the speed limit increase. Probabilities that passenger vehicles exceeded 85 and 90mph were non-significantly higher than expected within the 80mph zones. For large trucks, the mean speed and probability of exceeding 80mph were higher than expected within the 80mph zones. Only the increase in mean speed was significant. Raising the speed limit was associated with non-significant increases in speed variance. ConclusionsThe study adds to the wealth of evidence that increasing speed limits leads to higher travel speeds and an increased probability of exceeding the new speed limit. Results moreover contradict the claim that increasing speed limits reduces speed variance. Practical applicationsAlthough the estimated increases in mean vehicle speeds may appear modest, prior research suggests such increases would be associated with substantial increases in fatal or injury crashes. This should be considered by lawmakers considering increasing speed limits.

Traffic safety effects of new speed limits in Sweden

The effects of speed, both positive and negative, make speed a primary target for policy action. Driving speeds affect the risk of being involved in a crash and the injury severity as well as the noise and exhaust emissions. Starting 2008, the Swedish Transport Administration performed a review of the speed limits on the national rural road network. This review resulted in major changes of the speed limits on the rural road network. It was predominantly roads with a low traffic safety standard and unsatisfactory road sides that were selected for reduced speed limits, as well as roads with a good traffic safety record being selected for an increase in speed limits. During 2008 and 2009, speed limit changed on approximately 20,500km of roads, out of which approximately 2700km were assigned an increase, and 17,800km were assigned a reduction in speed limits.The aim of this study is predominantly to describe and analyse the longterm traffic safety effect of increased, as well as, reduced speed limits, but also to analyse the changes in actual driving speeds due to the changed speed limits. Traffic safety effects are investigated by means of a before and after study with control group and the effects on actual mean speeds are measured by a sampling survey in which speed was measured at randomly selected sites before and after the speed limit changes.Results show a reduction in fatalities on rural roads with reduced speed limit from 90 to 80km/h where the number of fatalities decreased by 14 per year, while no significant changes were seen for the seriously injured. On motorways with an increased speed limit to 120km/h, the number of seriously injured increased by about 15 per year, but no significant changes were seen for the number of deaths. The number of seriously injured increased on all types of motorways, but the worst development was seen for narrow motorways (21.5m wide). For 2+1 roads (a continuous three-lane cross-section with alternating passing lanes and the two directions of travel separated by a median barrier) with decreased speed limit from 110 to 100km/h, the seriously injured decreased by about 16 per year. As regards the change of mean speeds, a decrease in speed limit with 10km/h led to a decrease of mean speeds of around 2–3km/h and an increase of the speed limit with 10km/h resulted in an increase of mean speed by 3km/h. In conclusion, the results show that in total about 17 lives per year have been saved on the road network with changed speed limits. For comparison, 397 road users were killed in total during 2008. The number of seriously injured remain in principle unchanged. It should also be noted that the results are obtained for the road network which changed the speed limits during 2008 and 2009, and it is not certain that the results can be generalised to another road network.

Effects of vehicle power on passenger vehicle speeds

ABSTRACTObjectives: During the past 2 decades, there have been large increases in mean horsepower and the mean horsepower-to–vehicle weight ratio for all types of new passenger vehicles in the United States. This study examined the relationship between travel speeds and vehicle power, defined as horsepower per 100 pounds of vehicle weight.Methods: Speed cameras measured travel speeds and photographed license plates and drivers of passenger vehicles traveling on roadways in Northern Virginia during daytime off-peak hours in spring 2013. The driver licensing agencies in the District of Columbia, Maryland, and Virginia provided vehicle information numbers (VINs) by matching license plate numbers with vehicle registration records and provided the age, gender, and ZIP code of the registered owner(s). VINs were decoded to obtain the curb weight and horsepower of vehicles. The study focused on 26,659 observed vehicles for which information on horsepower was available and the observed age and gender of drivers matched vehicle registration records. Log-linear regression estimated the effects of vehicle power on mean travel speeds, and logistic regression estimated the effects of vehicle power on the likelihood of a vehicle traveling over the speed limit and more than 10 mph over the limit.Results: After controlling for driver characteristics, speed limit, vehicle type, and traffic volume, a 1-unit increase in vehicle power was associated with a 0.7% increase in mean speed, a 2.7% increase in the likelihood of a vehicle exceeding the speed limit by any amount, and an 11.6% increase in the likelihood of a vehicle exceeding the limit by 10 mph. All of these increases were highly significant.Conclusions: Speeding persists as a major factor in crashes in the United States. There are indications that travel speeds have increased in recent years. The current findings suggest the trend toward substantially more powerful vehicles may be contributing to higher speeds. Given the strong association between travel speed and crash risk and crash severity, this is cause for concern.

Evaluation of overtaking manoeuvres on two-lane rural roads

Two-way two-lane roads constitute a major proportion of rural road networks in Iran. The work described in this paper aimed to investigate the factors that influence overtaking manoeuvres using traffic conflict techniques to collect field data related to dangerous overtaking. The process of data collection was conducted by means of video recordings and other heuristic methods using inductive loop detectors. As one of the most important underlying independent variables, the percentage of time spent following was simulated. The classification and regression tree method (a common data mining approach) was used to identify important variables and explore the cut points of continuous variables. No-passing distance, road width, mean speed and vehicle time spent following were identified as the most important variables, and the results indicated a direct relationship between no-passing distance and the number of dangerous overtaking manoeuvres. Road widths less than the standard values and an increase in mean speed were also found to lead to an increase in the number of dangerous overtakings.

Nilsson's Power Model connecting speed and road trauma: Applicability by road type and alternative models for urban roads

Nilsson (1981) proposed power relationships connecting changes in traffic speeds with changes in road crashes at various levels of injury severity. Increases in fatal crashes are related to the 4 th power of the increase in mean speed, increases in serious casualty crashes (those involving death or serious injury) according to the 3 rd power, and increases in casualty crashes (those involving death or any injury) according to the 2 nd power. Increases in numbers of crash victims at cumulative levels of injury severity are related to the crash increases plus higher powers predicting the number of victims per crash. These relationships are frequently applied in OECD countries to estimate road trauma reductions resulting from expected speed reductions. The relationships were empirically derived based on speed changes resulting from a large number of rural speed limit changes in Sweden during 1967-1972. Nilsson (2004) noted that there had been very few urban speed limit changes studied to test his power model. This paper aims to test the assumption that the model is equally applicable in all road environments. It was found that the road environment is an important moderator of Nilsson's power model. While Nilsson's model appears satisfactory for rural highways and freeways, the model does not appear to be directly applicable to traffic speed changes on urban arterial roads. The evidence of monotonically increasing powers applicable to changes in road trauma at increasing injury severity levels with changes in mean speed is weak. The estimated power applicable to serious casualties on urban arterial roads was significantly less than that on rural highways, which was also significantly less than that on freeways. Alternative models linking the parameters of speed distributions with road trauma are reviewed and some conclusions reached for their use on urban roads instead of Nilsson's model. Further research is needed on the relationships between serious road trauma and urban speeds.

The effects of cannabis and alcohol on simulated arterial driving: Influences of driving experience and task demand

This study compared the effects of three doses of cannabis and alcohol (placebo, low and high doses), both alone and in combination, on the driving performance of young, novice drivers and more experienced drivers. Alcohol was administered as ethanol (95%) mixed with orange juice in doses of approximately 0, 0.4 and 0.6 g/kg. Cannabis was administered by inhalation of smoke from pre-rolled cannabis cigarettes (supplied by the National Institute of Drug Abuse, USA). Active cigarettes contained 19 mg delta-9-THC. Using a counterbalanced design, the simulated driving performance of 25 experienced and 22 inexperienced drivers was tested under the nine different drug conditions in an arterial driving environment during which workload was varied through the drive characteristics as well as through the inclusion of a secondary task. High levels of cannabis generally induced greater impairment than lower levels, while alcohol at the doses used had few effects and did not produce synergistic effects when combined with cannabis. Both cannabis and alcohol were associated with increases in speed and lateral position variability, high dose cannabis was associated with decreased mean speed, increased mean and variability in headways, and longer reaction time, while in contrast alcohol was associated with a slight increase in mean speed. Given the limitations of the study, it is of great interest to further explore the qualitative impairments in driving performance associated with cannabis and alcohol separately and how these impairments may manifest in terms of crash characteristics.

Quantifying movement demands of AFL football using GPS tracking

Global positioning system (GPS) monitoring of movement patterns is widespread in elite football including the Australian Football League (AFL). However documented analysis of this activity is lacking. We quantified the movement patterns of AFL football and differences between nomadic (midfield), forward and defender playing positions, and determined whether the physical demands have increased over a four season period. Selected premiership games were monitored during the 2005 ( n = 80 game files), 2006 ( n = 244), 2007 ( n = 632) and 2008 ( n = 793) AFL seasons. Players were fitted with a shoulder harness containing a GPS unit. GPS data were downloaded after games and the following measures extracted: total distance (km), time in various speed zones, maximum speed, number of surges, accelerations, longest continuous efforts and a derived exertion index representing playing intensity. In 2008 nomadic players covered per game 3.4% more total distance (km), had 4.8% less playing time (min), a 17% higher exertion index (per min), and 23% more time running >18 km h −1 than forwards and defenders (all p < 0.05). Physical demands were substantially higher in the 2008 season compared with 2005: an 8.4% increase in mean speed, a 14% increase in intensity (exertion index) and a 9.0% decrease in playing time (all p < 0.05). Nomadic players in AFL work substantially harder than forwards and defenders in covering more ground and at higher running intensities. Increases in the physical demands of AFL football were evident between 2005 and 2008. The increasing speed of the game has implications for game authorities, players and coaching staff.

The effects of typing speed and force on motor control in symptomatic and asymptomatic office workers

Office workers commonly suffer from Work-related Neck and Upper Limb Disorders (WRNULD) due to prolonged computer use. The speed and force performance in the keystroke actions are important elements in motor control that can be influenced by musculoskeletal symptoms. This study examined the keystroke performance of symptomatic and asymptomatic office workers when they were challenged by the demands of increased speed and force of keyboard operation. Two groups of female office workers were compared in terms of their keystroke dynamics during three typing conditions which involved normal typing speed and force (“Normal”), typing with increased speed (“Faster”) and typing with increased force (“Harder”). The results showed that both the Case Group ( n = 21 ) and the Control Group ( n = 20 ) performed with similar levels of Mean Speed and Mean Peak Force in the Normal condition. The Case Group subjects reported significantly increased discomforts in the Faster and Harder conditions but not the Control Group. In the Faster condition, the Case Group showed trends for greater Speed and Force Variability. In the Harder condition, the Case Group showed more associated increase in Mean Speed while achieving a lower increase in Mean Force. These differences were even more apparent when Case Group was sub-divided into High-Low Discomfort sub-groups. The results may suggest a relationship between musculoskeletal discomforts and the speed and force control in keystroke actions. Relevance to Industry The control of speed and force in typing are important components of occupational exposure in office workers, and they may have implications towards explaining why some workers get WRNULD and others do not. The results suggest that symptomatic individuals may respond differently when ergonomic interventions are introduced.

Short-duration robotic therapy in stroke patients with severe upper-limb motor impairment

Chronic motor deficits in the upper limb (UL) are a major contributor to disability following stroke. This study investigated the effect of short-duration robot-assisted therapy on motor impairment, as measured by clinical scales and robot-derived performance measures in patients with chronic, severe UL impairments after stroke. As part of a larger study, 15 individuals with chronic, severe UL paresis (Fugl-Meyer < 15) after stroke (minimum 6 mo postonset) performed 18 sessions of robot-assisted UL rehabilitation that consisted of goal-directed planar reaching tasks over a period of 3 weeks. Outcome measures included the Fugl-Meyer Assessment, the Motor Power Assessment, the Wolf Motor Function Test, the Stroke Impact Scale, and five robot-derived measures that reflect motor control (aiming error, mean speed, peak speed, mean:peak speed ratio, and movement duration). Robot-assisted training produced statistically significant improvements from baseline to posttreatment in the Fugl-Meyer and Motor Power Assessment scores and the quality of motion (quantified by a reduction in aiming error and movement duration with an increase in mean speed and mean:peak speed ratio). Our findings indicate that robot-assisted UL rehabilitation can reduce UL impairment and improve motor control in patients with severe UL paresis from chronic stroke.

Swimming changes and chemotactic responses in Rhodobacter sphaeroides do not involve changes in the steady state membrane potential or respiratory electron transport

The effect of the chemoattractants acetate, propionate, pyruvate and potassium on the steady state membrane potential and the rate of respiratory electron transport was examined in Rhodobacter sphaeroides. Under conditions where the membrane potential makes up most of the proton motive force, all attractants increased the steady state membrane potential in the dark. However, only potassium was able to consistently increase the steady state membrane potential in the light. All of the attractants were able to increase the mean swimming speed of cells at high light levels for prolonged periods, showing that the increase in mean speed cannot be caused by an increase in the membrane potential. Measurement of chemotaxis in wells showed a positive response to propionate in the dark, at low light (10 – 20 μmol photons m−2 s−1) and in high light (700 μmol photons m−2 s−1). The demonstration of chemotaxis in the dark precluded any direct role of photosynthetic electron transport in chemotaxis. The response at high light, where there was no induced change in membrane potential, confirmed that the steady state membrane potential was not involved in tactic signalling. Acetate, propionate and pyruvate at appropriate concentrations stimulated the rate of respiratory electron transport in the dark, while potassium had no effect. In low light, all three organic acids caused a significant stimulation of respiratory electron transport but potassium caused a significant inhibition. In high light, only pyruvate and propionate caused a significant increase in the rate of respiratory electron transport. Chemoattractants can therefore produce a significant positive tactic response when respiratory electron transport is either unaffected or inhibited. These data show that neither a change in the bulk steady state membrane potential nor the rate of respiratory electron transport causes either the change in swimming behaviour or acts as a chemotactic signal.