Tram Speed Research Articles

FEM and field tests to study the dynamic response of composite pavement surrounding embedded tram tracks to moving loading: implications to fatigue cracking

Under long-term tram loads, cracking occurs on the composite pavement surrounding an embedded tram track. However, in the current pavement design of the shared right-of-way section of a tram track, the trackside pavement fatigue characteristics are not considered. The investigation of the real dynamic strain response of the trackside composite pavement under tram loads is crucial for pavement system design. In this paper, a three-dimensional finite element model of tram-track- composite pavement was established. The rationality of this model was verified by a field pavement dynamic test. The influence of the track irregularity and tram speed on the dynamic characteristics of the pavement surrounding the track was explored. The trackside pavement strain distribution along the longitudinal and vertical directions of the track had been studied. The high-frequency strain components caused by the random shortwave track irregularity excitation were found in the strain frequency domain curves in different directions, and the track irregularity amplifies the influence of the tram speed on the surrounding pavement dynamic response. The loading frequency is an important input for determining the dynamic model and fatigue characteristics of asphalt materials. At the same time, the lab test loading frequency and fatigue life corresponding to the mixture were calculated by the mechanistic coupled model and empirical damage evolution equation. It provides an analytical base for the design of pavement surrounding embedded tram tracks.

Assessment of Pedestrians' Head and Lower Limb Injuries in Tram-Pedestrian Collisions.

Analysis of pedestrians' head and lower limb injuries at the tissue level is lacking in studies of tram-pedestrian collisions. The purpose of this paper therefore to investigate the impact response process and severity of pedestrians' injuries in tram-pedestrian collisions, using the Total Human Model for Safety (THUMS) pedestrian human body model together with the tram FE model. Two full-scale tram-pedestrian dummy crash tests were performed to validate the FE model, and the total correlation and analysis (CORA) score of head acceleration yielded values of 0.840 and 0.734, confirming a strong agreement between the FE-simulated head responses and the experimental head kinematics. The effects of different tram speeds and impact angles on pedestrians' impact response injuries and the differences were further analyzed. The results indicate that direct impact of the lower limb with the tram's obstacle deflector leads to lower limb bone shaft fractures and knee tissue damage. Neck fling contributed to worsened head injury. Coup contusions were the predominant type of brain contusion, surpassing contrecoup contusions, while diffuse axonal injury was mainly concentrated in the collision-side region of the brain. Pedestrians' injuries are influenced by tram velocity and impact angle: higher tram velocities increase the risk of lower limb and head injuries. The risk of head injury for pedestrians is higher when the impact angle is negative, while lower limb injuries are more significant when the impact angle is 0°. This study provides practical guidance for enhancing tram safety and protecting pedestrians.

Analysis of the wheel-rail dynamic response characteristics and damage to the fixed frog of the No. 3 tram turnout

The tram No. 3 turnout fixed frog uses a variation in the depth of the flange groove so that the wheel rolls over the frog area in a continuous flange bearing. This method of travelling over the turnout requires the wheel load to transition back and forth between the tread and the flange, resulting in wheel-rail impact, which in turn affects service life. In order to investigate its service characteristics, this paper has established a transient wheel-rail rolling contact finite element model for the No. 3 turnout fixed frog. The macroscopic dynamic response and microscopic wheel-rail contact solution as the tram passes through the turnout at different axle weights and speeds are analysed in detail, and the changing patterns of wear and fatigue damage are investigated. The research shows that rail wear is particularly severe in the wheel flange bearing area, approximately 1.6 times greater than in the tread bearing area. In addition, when tram speeds are reduced to 15 km/h, there is a significant reduction in wheel-rail impact and wear, thereby improving ride smoothness and safety. The results of this study are of great significance to the operation and maintenance of the No.3 fixed frog turnout.

An Energy Flow Control Algorithm of Regenerative Braking for Trams Based on Pontryagin’s Minimum Principle

Energy savings in electric rail transport are important in order to increase energy efficiency and reduce its carbon footprint. This can be achieved by storing and using the energy generated during regenerative braking. The system described in this paper consists of a supercapacitor energy storage system (SC ESS), a bidirectional DC/DC converter, and an algorithm to control the energy flow. The proper design of the algorithm is critical for maximizing energy savings and stabilizing the power grid, and it affects the lifetime of the SC ESS. This paper presents an energy flow control algorithm based on Pontryagin’s minimum principle that balances maximum energy savings with maximum SC ESS lifetime. The algorithm also performs SC ESS recharging while the rail vehicle stops on inclines to reduce the impact of its next acceleration on the power grid. To validate the algorithm, offline simulations are performed using real tram speed measurements. The results are then verified with a real-time laboratory emulation setup with HIL simulation. The tram and power grid are emulated with LiFePO4 batteries, while the SC ESS is emulated with a supercapacitor. The proposed algorithm controls a three-phase converter that enables energy exchange between the batteries and the supercapacitor. The results show that the proposed algorithm is feasible in real time and that it can be used under real operating conditions.

Effect of polygonal wheel on the vehicle-track dynamic interaction in turnout and its transmission to the trailer bogie wheels

The dynamic interaction between the vehicle and track is strongly influenced by out-of-round wheels and turnout rail profile geometries, which result in high-magnitude contact forces and abnormal vibrations. This study presents the dynamic response of the tram-turnout interaction due to polygonal wheel wear and analyses its transmission between the wheelsets. A three-dimensional coupled tram-turnout dynamic model was formulated, taking into account the polygonal wear on the front bogie wheelsets. Through numerical simulations, the dynamic characteristics of a tram passing through the turnout switch and crossing panels under the influence of polygonal wear were simulated. Furthermore, the impact of polygonal wear amplitudes and tram speeds on the transmission of dynamic impact forces and vibrations from the front bogie wheelset to the trailer bogie wheels are described. According to the numerical findings, when the flexible wheelset experiences polygonal wear, it can lead to substantial impact forces and vibrations as the tram moves through the turnout switch and crossing zones. Moreover, the transmission of dynamic impact forces and vibrations from the front bogie wheelset to the trailer wheels increases as the wheel wear amplitude and the vehicle speed increase.

The Use of the Imperialist Competitive Algorithm in Optimising the Setting of the Tram Speed Controller in the Development of a Matlab-Simulink Environment

Estimating the electric power used by railway vehicles is an important factor in the planning of future power consumption, looking for possibilities to reduce the use of electric power and therefore also reduce carbon emissions. To improve the estimation, we used the imperialist competitive algorithm in the optimisation process of a mathematical model of a tram vehicle. Specifically, in the setting of the proportional and summation constant of the vehicle speed controller which emulates the activity of the driver in the simulation. Our work presents a new approach to optimising the estimation of energy consumption in tram transport. The method used is based on mathematical modelling and simulation of social development in human society. To obtain the input data for the simulation, we performed a measurement of the reference speed by means of a GPS receiver located in a sample tram vehicle. Subsequently, to verify the model and energy calculation results, we measured the output currents and voltage from the traction converter station at the corresponding time. Our method achieved a 93 % match between the measured and simulated power consumption.

Efficient mitigation of railway induced vibrations using seismic metamaterials

The fast growth of railway transport pushed by its sustainability requires all railway stakeholders to work together to minimise any possible drawbacks that might slow down this positive trend. Among these, the induced vibrations generated at the wheel–rail interaction during train passage are the most significant, especially in urban areas where in the form of ground-borne vibrations and/or noise negatively affects the daily life of the residents. In this direction, the innovative concept of seismic metamaterial can enhance the vibration attenuation levels of existing mitigation measures and, at the same time, ensure a straightforward application in the railway environment. This paper uses a combined vehicle/track/soil prediction dynamic model of the T2000 LRV (Light Rail Vehicle) tram operating in Brussels, based on a two-step approach already validated in the past, to analyse the effects that the inclusion of seismic metamaterials within the transmission path has in terms of vibration attenuation. In particular, a four-by-four group of piles is examined with different material proprieties for the inclusions, considering a range of velocities and distances from the track in order to quantify the achievable Insertion Loss (IL) for each configuration depending on the distances and the tram speed, attaining ILs up to 10 [dB]. The study is then extended to other possible arrangements of the group of piles, providing a direct relationship between the repetitiveness of each row of the primitive unit cell of the metamaterial and the gained levels of attenuation, in order to give a base for the costs of this type of mitigation measure. Furthermore, the influence on the attenuation levels of the soil characteristics, is evaluated by considering an ideal uniform underground, extending the IL to 18 [dB] in the case of steel inclusion. Finally, the paper gives insights into the use of metamaterials as mitigation measures for railway-induced vibration in order to understand and evaluate the potential of this novel concept and its benefits.

The impact of mobility characteristics on public transport and road safety performance in selected European cities

The aim of this paper is to investigate the impact of mobility characteristics on Public Transport (PT) and road safety performance. For this purpose, data for several large European cities on population, road network, traffic, mobility and road fatalities were collected from the European Metropolitan Transport Authorities’ reports and the European CARE database. Initially, a database was developed containing data for the period 2014–2018 and then, two linear regression models were developed. The results of the first model indicate that more bus and tram stops, increase in GDP, higher population density and PT public operation have a positive impact on PT demand, while the opposite is the case for increases in car ownership and PT fares. Based on the second model, it is revealed that increases in population density, bus and tram stops, modal share of active travelling modes, GDP and tram speed lead to road fatalities’ decrease.

Energy-efficient tram speed trajectory optimization considering the influence of the traffic light

The tram typically adopts the form of semi-independent right of way, which is affected by the traffic light at junctions. The parking and wait time of the tram due to red lights will increase the energy consumption and reduce the passenger comfort. This paper proposes a speed trajectory optimization approach for the tram without parking when encountering a red light. This approach is realized by reasonably adjusting the running time and speed of the tram between two adjacent sections bounded by the traffic light at the junction, on the premise that the total travel time of the whole section remains unchanged. In the model, the constraints of tram movement, speed limits, and line conditions are considered. Moreover, considering the influence of the traffic light, the comfort and traffic light constraints are added to establish the energy-efficient tram speed trajectory optimization model. The nonlinear constraints in the optimization model are converted to linear constraints using the segmental approximation method and adding constraints. As a result, the optimization model is reformulated into a mixed-integer linear programming model, which could be solved by a commercial solver like CPLEX. Numerical experiments are conducted with a 3,660 m long section of the tram line with the traffic light at the junction. The experimental results show that the speed trajectory optimization approach considering the influence of the traffic light proposed in this paper can reduce the total energy consumption by 23.46% and improve passenger comfort.

Pedestrian fatality risk as a function of tram impact speed

Abstract The objective of the presented research-work was to develop a model to describe the risk of fatal accident involving tram and pedestrian. This study extends research concerning relationships between the “impact speed” and probability of pedestrian death in case of tram accident. Over 400 “tram-pedestrian” accidents were analyzed. Logistic regression analysis was used in these studies. The main objective of the research is to compare the risk of fatal accidents when pedestrians are struck by passenger cars and trams. GPS system from trams is used to analyze correlation between the tram speed and different conditions along the public transport stop areas (e.g. traffic signals, priority, and platforms localization). The results show that the fatal risk of hitting pedestrians by a tram running at a speed of 50 km/h is two and a half times greater than that by a car. Research clearly proves that comparing to car impact speed, there is much higher probability of death when pedestrian is hit by a tram running at a speed of 30 km/h – almost 40% (compared to 5% when hit by car). There are even cases of deaths with a very low speed of tram (5–10 km/h).

Concept for an event-triggered wireless sensor network for vibration-based diagnosis in trams

Trams are the most durable and resource efficient forms of public transportation. However, because of the varying wear in dependence on their operation mode and load levels, there is a need for condition monitoring and early maintenance. Vibration sensors provide interesting possibilities to monitor the relevant tram drive components. In this contribution we investigate their use under real conditions. On the basis of cable bound vibration measurements, the influence of the crossed track section, the tram speed and the tram condition is shown. Based on the investigation results, a concept is proposed in which a meshed and wireless sensor network, event-triggered, can acquire vibration measurement data, which are suitable for the diagnosis of tram drive components. The proposed concept has the potential to operate the sensor nodes in an energy efficient way through decentralized data evaluation taking place on the sensor node.

Field investigation to measure airflow velocities of a shuttle car using independent routes at a central Appalachian underground coal mine.

Canopy air curtains on roof bolting machines have been proven to protect miners from respirable dust, preventing their overexposure to dust. Another desired application for canopy air curtains is in the compartments of shuttle cars. The challenges faced in developing the design of canopy air curtains for shuttle cars include mine ventilation rates in tandem with the shuttle car tram speeds. The resulting cab airspeeds may exceed 182 m/min (600 fpm), as found in the present study conducted in a central Appalachian underground coal mine by U.S. National Institute for Occupational Safety and Health (NIOSH) researchers. Prior research and laboratory testing had indicated that successfully protecting a miner in high air velocities is difficult, because the clean air from the canopy air curtain is unable to penetrate through the high-velocity mine air. In this study, the dust concentrations to which a shuttle car operator was exposed were measured, and air velocities experienced by the operator were measured as well using a recording vane anemometer. The results indicate that the highest exposure to respirable dust, 2.22 mg/m3, occurred when the shuttle car was loading at the continuous miner, where the average airspeed was 48 m/min (157 fpm). While tramming, the operator was exposed to 0.77 mg/m3 of respirable dust with an average airspeed of 62 m/min (203 fpm). This study indicates that a canopy air curtain system can be designed to greatly reduce an operator's exposure to respirable dust by providing clean air to the operator, as the majority of the operator's dust exposure occurs in air velocities slower than 61 m/min (200 fpm).

Optimization of fuel-cell tram operation based on two dimension dynamic programming

This paper proposes an optimal control strategy based on the two-dimension dynamic programming (2DDP) algorithm targeting at minimizing operation energy consumption for a fuel-cell tram. The energy consumption model with the tram dynamics is firstly deduced. Optimal control problem are analyzed and the 2DDP strategy is applied to solve the problem. The optimal tram speed profiles are obtained for each interstation which consist of three stages: accelerate to the set speed with the maximum traction power, dynamically adjust to maintain a uniform speed and decelerate to zero speed with the maximum braking power at a suitable timing. The optimal control curves of all the interstations are connected with the parking time to form the optimal control method of the whole line. The optimized speed profiles are also simplified for drivers to follow.

Infrastructure and Operational Influences on Collisions Between Trams and Left-Turning Cars

This research identified infrastructural and operational factors that influenced the most common type of car–tram collision: cars making opposing turns in front of trams. Few studies have analyzed influences on car–tram collisions quantitatively, but none have explored predictor factors for opposing-turn crashes—a research gap addressed with this paper. The two largest Swiss tram networks, Basel and Zurich, were used for the analysis. A point-based research approach was chosen: all locations within a tram network at which a car could turn left (an opposing turn where traffic drives on the right) in front of a tram were identified. For each of these points, data on dependent and predictor variables were collected. This data set was analyzed with Poisson, negative binomial, and zero-inflated negative binomial regression models. The number of left-turning car–tram collisions was used as the dependent variable, while predictors were derived from a literature review; models were fitted by using all predictors and with forward variable selection by means of Akaike’s information criterion. Traffic volumes (cars and trams), tram speed, and dedicated left-turn lanes were found to be significantly associated with a higher frequency of car–tram collisions, whereas turning left to access a service rather than a road, left-turn restrictions, proximity to a tram stop, and perpendicular turning angles were significantly associated with a lower frequency of left-turning car–tram collisions. On the basis of these results, left turns across tramways should be restricted for cars. Remaining conflict points should be located close to tram stops, have limited tram speed, and feature perpendicular turning angles.

Mechanism and affecting factors of Translohr tramway guide rail side wear

The wheel–rail contact can be found in two patterns. In the first pattern, the treads of both wheels are in contact with the two top surfaces of the ^-shaped guide rail; in the second pattern, the treads of both wheels are in contact with the two top surfaces of the ^-shaped guide rail, and the wheel edge is in contact with the guide rail web on one side. Based on these findings, an equivalent mechanical model with four unilateral springs is proposed to describe the wheel–rail contact. Additionally, a dynamic model of the Translohr tramway is established using Matlab/Simulink. The wheel–rail contact in a tramway moving along curves with different radii is calculated using simulation, and the results obtained are consistent with the observations and results of field measurements. The effects of various factors, including curve radius, tram speed, guide rail pre-pressure, and guide rod length, on the side wear of the guide rail were investigated. The results revealed that curve radius and tram speed are the critical factors affecting rail track side wear. These two factors can qualitatively determine rail track side wear, while other factors can only quantitatively affect the degree of rail track side wear.

In situ measurement of the acoustic performance of a full scale tramway low height noise barrier prototype

The acoustic performance of a full scale low height barrier prototype meant to attenuate tramway noise is measured in situ. The prototype is made of an inverted L-shape assembly of pressed wood boards covered on the source side with fibrous absorbing material, and has been set up temporarily in a residential area in the town of Saint-Martin-d’Hères, near Grenoble (France), through which a tramway line passes. A series of pass-by level measurements were made at a close receiver location corresponding to the typical height of human ears, with and without the device. The tram speed has also been measured using an auxiliary microphone located very close to the track. A significant variability in pass-by levels has been found between the different trams, even when applying an approximate correction for speed. However it is shown that the barrier provides on average an attenuation of more than 10dB(A) for the trams closest to the barrier, during the whole pass-by. Spectral analysis of the recorded signals is also carried out to estimate the barrier insertion loss more accurately. Furthermore, comparisons between measurements and BEM calculations show that numerical predictions can yield rather good estimates of the actual in situ performance, within a few dB(A).

Prediction of noise from trams

An improved calculation model for the prediction of levels of noise from trams is presented. The model is based on current calculation models for noise from trams and the measurements of equivalent noise levels from trams carried out in Kos̆ice, Slovakia. The data were processed using correlation and regression analysis and besides already known factors (the number of tram sets passing a certain location per hour, tram speed, the type of tram rail, the tramline gradient), several new factors (wavelength of rail corrugations and rail grinding, the age of the tramcars and tramlines and the detailed composition of tram sets) have been included in the presented calculation model for the prediction of levels of noise from trams.