Truck Escape Ramp Research Articles

Investigating the Influence of Varied Particle Sizes on the Load-Bearing Properties of Arrester Bed Aggregates.

This study employs the discrete element method to investigate the influence of particle size on the load-bearing characteristics of aggregates, with a specific emphasis on the aggregates used in escape ramp arrester beds. This study utilises the log edge detection algorithm to introduce an innovative approach for modelling irregularly shaped pebbles, integrating their physical properties into a comprehensive discrete element model to enhance the accuracy and applicability of simulations involving such pebbles. Meticulous validation and parameter calibration (friction coefficient: 0.37, maximum RMSE: 3.43) confirm the accuracy of the simulations and facilitate an in-depth examination of the mechanical interactions between aggregate particles at macroscopic and microscopic scales. The findings reveal a significant relationship between the particle size and load-bearing capacity of aggregates. Smaller pebbles, which are more flexible under pressure, can be packed more densely, thereby improving the distribution of vertical forces and increasing the concentration of local stress. This enhancement substantially increases the overall load-bearing capacity of aggregates. These discoveries hold significant implications for engineering practices, particularly in the optimisation of safety for truck escape ramps and in identifying the ideal sizes of pebbles with irregular shapes.

Analysis of the Load-Bearing Capacity of Pebble Aggregates

The load-bearing capacity of pebble aggregates plays a pivotal role in influencing the operational performance of uncontrolled trucks on arrester beds. The complexity of this phenomenon stems from the nonuniformity in the shapes of the pebbles and their stochastic arrangement within the beds, presenting notable challenges for traditional mathematical modelling techniques in precisely evaluating the contact dynamics of these aggregates. This study leverages the discrete element method (DEM) to extensively analyse the arrester bed aggregate of a standard truck escape ramp. The aforementioned mechanism entails the gathering of morphological parameters of irregularly shaped aggregate particles and introduces a novel method for constructing random shapes that adhere to the observed distribution characteristics. A discrete element model, grounded in the physical properties of these aggregates, is formulated. This study focuses on the aggregate’s load-bearing capabilities, scrutinising the mechanical behaviour of the aggregate particles at the macroscopic and microscopic scales. These insights offer substantial scientific contributions and practical implications for assessing the safety of escape ramps and determining essential parameters for the brake bed design.

Performance and Geotechnical Properties of the Aggregates Used for the Turkish Trans-European Motorway Truck Escape Ramps

Performance and Geotechnical Properties of the Aggregates Used for the Turkish Trans-European Motorway Truck Escape Ramps

Influence of Aggregate Pollution in Truck Escape Ramps on Stopping Distance of Uncontrolled Vehicles

Migration of fine materials such as soil from the roadbed and the ground will gradually pollute the aggregate in the arrester bed of truck escape ramps. However, there are few studies on the impact of aggregate pollution of the arrester bed on the stopping distance of runaway vehicles. This paper uses the discrete element method to study the influence of aggregates with different degrees of pollution on stopping distance by taking silty cohesive soil as a typical pollutant. In this paper, the stopping process of the uncontrolled vehicle on the arrester bed with different pollution levels was numerically simulated. The simulation results show that the uncontrolled vehicle’s stopping distance increases with the contaminated aggregate’s soil content. The simulation results show that when the soil content in the contaminated aggregate is less than 15%, the increase in the stopping distance of the uncontrol vehicle is less than 5%; when the soil content is 20–25%, the stopping distance of the uncontrolled vehicle increases by more than 20%; and when the soil content is 30–35%, the stopping distance of uncontrol vehicle increases by more than 50%. Different maintenance measures should be taken according to the increase in stopping distance.

Method for Estimating Speed of the Out-of-Control Tractor-Semitrailer on Downhill Grades

Speed estimation for the out-of-control truck on a downhill grade is essential for passive safety features like truck escape ramps to promote traffic safety. This paper presents a method for estimating the speed of out-of-control trucks based on Newton’s Laws of Motion. First of all, we analyze gravity effort, aerodynamics, and rolling resistance through a free body diagram of an out-of-control truck on a downhill grade. Further, we select the speed as the dependent variable, with the following road and vehicle characteristics as independent variables: road surface type, grade, grade length, truck size, truck weight, and tire type. Finally, we estimate the speed and acceleration according to Newton’s Laws of Motion. The results show that the factors that significantly affect the out-of-control truck’s speed include tire type, road surface coefficient, grade, and grade length. TruckMaker simulation results demonstrate that the model is valid at a 99% confidence level.

Simulation research on the protection performance of fall protection net at the end of truck escape ramp.

Although the fall protection net installed at the end of the truck escape ramp has a protective effect on trucks and drivers, but lacks sufficient theoretical basis and verification method. The primary objective of this paper was to design a fall protection net that meets the regulations and research its protection performance. The finite-element method was used to design the overall size, material, mesh length, mesh type, shape, and supporting structure of the fall protection net installed at the end of truck escape ramp, then dummy and truck models were used to impact the fall protection net to verify the rationality of the design. After the design completed, the truck model was used to impact the fall protection net twice to research the cumulative protection performance. A fall protection net with a width of 6000 mm, a span of 6000 mm, a depth of 5196 mm, a mesh length of 150 mm, a mesh type of diamond mesh, a shape of 60-degree V-shaped, a supporting structure of steel pipe supporting has a better effect on energy absorption and protection. Within the two consecutive impacts, the residual plastic deformation and stress of the fall protection net generated in the first impact severely affect the protection performance in the second impact. It is feasible to use the finite-element method to design and research the fall prevention net installed at the end of the truck escape ramp, and the fall protection net can indeed protect the trucks and drivers, and it should be inspected and maintained after impact to ensure the protective performance in subsequent use.

Three-dimensional discrete element simulation of the runaway vehicle deceleration process on the arrester bed of truck escape ramps.

Due to imperfect design norms and guidelines for China's truck escape ramp, previous studies have not been able to reflect the effect of wheel subsidence process on the deceleration of runaway vehicles. A discrete element method was used to establish an aggregate discrete element and a wheel discrete element. The three-dimensional discrete element model for an aggregate-wheel combination was established based on a particle flow code in three dimensions on a software platform using the "FISH" language. The microscopic parameters of the aggregate discrete element particles and wheel discrete element particles were calibrated using a simulated static triaxial compression test and real vehicle test data, respectively. Four sets of numerical simulation tests were designed for analyzing the influence of the aggregate diameter, grade of the arrester bed, truckload, and entry speed on the wheel subsidence depth and stopping distance of runaway vehicles. The results indicate that the smaller the aggregate diameter and entry speed and the greater the truckload and grade of the arrester bed, the more easily the wheel falls into the gravel aggregate, the better the deceleration effect, and the smaller the stopping distance. As the wheel subsidence depth increases, the speed at the unit stopping distance decreases more quickly. The maximum subsidence depth mainly depends on the truckload. The research results can provide a theoretical basis for the design of the arrester bed length and the thickness of the aggregate pavement in a truck escape ramp.

Three-dimensional discrete element modeling of the irregularly shaped pebbles used in a truck escape ramp

The truck escape ramp is a clump of pebbles that is located alongside downgrades. As the pebbles are randomly placed in arrester beds, few studies have been conducted on simulation methods of the irregularly shaped pebbles. This paper proposed a pebble DEM model to analyze the micro-contact mechanism of the pebbles. Based on a polynomial algorithm, the 7th fit was selected and the coefficients of the edge curves were recorded. Second, the main view and left view were filled with preset numbers of ball elements. According to the ball element parameters, the ball elements were extended to three-dimensional models. Third, based on the edges of the main view and the top view, the ball element parameters were recalculated. Then, compression tests were conducted, and the key parameters of the pebble DEM model were calibrated. Based on the built pebble DEM model, compression tests were simulated with different pressing plate velocities and laying thicknesses. The results indicate that for increases in the pressing plate velocity, the contacting forces on the plate correspondingly increase, and this increase is linearly shaped. The results for different laying thicknesses indicate that for increases in the laying thickness, the contacting forces on the plate correspondingly decrease.

Reliability-based design of truck escape ramps

The design method of truck escape ramps (TERs) presented by the Transportation Association of Canada and other organizations is deterministic and assumes fixed values of the design speed, rolling resistance, and ramp grade. This paper presents a reliability-based method for TER design based on the first-order second-moment (FOSM) method and the advanced FOSM (AFOSM) method. These methods rely on the distribution of the component random variables. Each method was used to analyze a TER with one grade and two grades. The FOSM is simple and can be easily used by practitioners, even with calculators. The AFOSM is more complicated but more accurate as it considers the design points in determining the probability of failure. The AFOSM method was used to establish design graphs for the required length of TERs. Application of the proposed method is illustrated using actual TERs in the United States and considering a hypothetical design scenario.

Simulation of finding the optimized gravel radius of the arrester bed on truck escape ramp

Propose a simulation method of finding the optimized gravel radius of the arrester bed on truck escape ramp in order to obtain the shortest stopping distance of runaway vehicle. A simulation model between gravel and tire is generated and calibrated by PFC2D (Particle Flow Code in two-dimensions) respectively. Utilize the model to simulate the relationship between radius and stopping distance at varied slopes and initial vehicle speeds. Simulation shows that whatever the slopes and the speeds are, the shortest stopping distance corresponds to gravel radius range is between 8.3mm and 15.7mm, that average radius is 12mm. The average radius is basically consistent with the ideal gravel radius 12.7mm, which indicates that the method is effective and could be a substitute for the full-scale test.

Analyzing the Influence of Aggregate Properties on Stopping Distance on Truck Escape Ramps

Although there are many studies involving influence of runaway truck entry speed and longitudinal grade on stopping distance, focusing on aggregate properties is scarce. This paper investigates the influence of the aggregate properties such as types of aggregate and river gravel radius on stopping distance through numerical analysis of particle flow code in two dimensions (PFC2D). The software is used to generate stopping distance data for two aggregate types and four group gravel radii under various approaching speeds and grades. The generated data are compared with the testing results of full-scale arrester bed. The simulated finding of this paper implies that types of aggregates and river gravel radii have a significant impact on the stopping distance for runaway truck on escape ramps.

Numerical study of the stopping distance for runaway vehicle on truck escape ramp by using the improved equation of car driving

The stopping distance of the runaway vehicle on the mountain road directly affects the length design of the arrester bed. Since the subsidence depth of runaway vehicle wheel on the arrester bed is neglected in the past researches, the stopping distance estimated by the vehicle driving equation is not accurate. The purpose of this paper is to supplement the influence of subsidence depth on rolling resistance and the influence of mountain highway altitude on air resistance, and improve the estimation accuracy through improved vehicle driving equation. Firstly, the formula for fitting the subsidence depth is established, and the formula for calculating the pushing resistance and compaction resistance is added. Considering the influence of the altitude of the mountain road on the air resistance, the formula for calculating the corrected air resistance and the air lift is added too and the improved vehicle driving equation is generated. Secondly, a simulink model is established based on the improved vehicle driving equation and determine the attester bed entering position and the initial entering speed of the runaway vehicle. Finally, the simulation model is run and analysed. The results show that the error rate of the simulation results is less than 8.0% compared with the full-scale test data. Compared with original equation, the shortening rate of the stopping distance is up to 85.59%.

On the Effective Speed Control Characteristics of a Truck Escape Ramp Based on the Discrete Element Method

This paper presented a numerical analysis of the damping characteristics of truck escape ramps. To explore the procedure of out-of-control trucks running into arrester beds, the discrete element method (DEM) models of both the tire and the truck escape ramp were built. Tire compression tests were conducted on a homemade tire test system, and the results were used to calibrate the parameters of the tire DEM model. A compression machine was used to conduct dynamic compression tests on pebbles obtained from escape ramps, and the results were used to calibrate the parameters of the pebble DEM model. Road tests were then conducted to further validate the simulation method. An adaptive master-slave simulation procedure analysis was utilized in the simulation process. The error of the travel distance between the simulation and test results was 2.95%. The built tire-pebble DEM model was used to perform the simulations of trucks running into truck escape ramps with different truckloads and laying depths. The results of different truckloads indicated that the truck speed was mainly determined by the laying depth at the entrance of the truck escape ramp. With an increase in time, the truckload started to take effect. The results of different laying depths indicated that the truck speed results were approximately constant at the entrance of the truck escape ramp. As the laying depth increased, the truck speed decreased. When the laying depth exceeded approximately 60 cm, the damping properties of the different laying depths were approximately constant.

Discrete Element Analysis of the Reconstruction Method for Randomly Shaped Pebbles

The pebble shape is a critical factor that affects the bearing characteristics of truck escape ramps. In this paper, a reconstruction method was proposed for randomly shaped pebbles used in truck escape ramps, and statistical analysis was conducted on the results of pebble compression tests. First, 100 pebble samples were randomly selected, and the pebble outlines were fitted in three views. The overlapping method was implemented to fill the three views with ball elements, and the ball elements were then extended into three-dimensions. The results demonstrated that the proposed method satisfactorily monitored the real pebble shapes. Second, statistical analyses were conducted on the parameters of the outlines, and corresponding data sets were built. The key parameters of the pebble DEM model, such as the friction coefficient, were calibrated based on the compression test results, and repeated simulation results verified the feasibility of the proposed pebble DEM model. Next, statistical analysis was conducted on the probability distribution of the contact forces. Third, simulations were conducted with different pressing plate velocities and pebble shapes. The results indicated that the pressing plate velocities had minor effects on the contact forces. As the pressing plate velocity increased, the slope of the contact forces correspondingly increased. The particle shape was a critical factor affecting the simulation results. With the same contact parameters, the simulation results of different pebble shapes varied greatly, which further indicated the importance of the proposed pebble shape reconstruction method. The proposed pebble DEM model could be further used in the design of truck escape ramps.

Prediction Model for Brake-Drum Temperature of Large Trucks on Consecutive Mountain Downgrade Routes Based on Energy Conservation Law

Excessively high brake temperature may lead to brake fading and failure, resulting in truck runaway down a graded descent. The accurate prediction of the changes in the brake-drum temperature on downgrades can provide theoretical guidance for truck accident countermeasures, such as determining the maximum safe speeds and the locations of truck escape ramps. By analyzing truck accident mechanisms during graded descents and selecting the initial brake-drum temperature, downgrade percentage and length, and the truck weight and speed as independent variables, with the brake-drum temperature as a dependent variable, the downgrade process of a truck can be divided into two stages: speed control at the grade section and emergency braking at the grade end. The energy conversion process in the forms of brake and nonbrake forces in the two stages are analyzed, based on the energy conservation law. A prediction model for the brake-drum temperature of large trucks on consecutive mountain downgrade routes is established, using the heat quantity formula. The model’s numerical calculation explicitly demonstrates the effect of all the variables. The brake-drum temperature is positively related to the truck weight, and the percentage and length of the downgrade. The temperature increase in the control speed phase is negatively related to the truck speed, whereas that in the emergency braking phase is positively related. The relationship curves between the variables show that the brake-drum temperature does not change significantly with the truck speed. However, the brake-drum temperatures, under different truck weights, downgrade lengths, and percentages, at the same speed, differ considerably. Compared to the existing empirical fitting model based on specific test data, the proposed model clearly shows the effects of main variables. The proposed model can be used for determining the safe truck speeds and locations of truck escape ramps to provide guidance for drivers and builders.

Influence of Main Road Alignment on Handling Stability of Runaway Vehicle on Truck Escape Ramp

Main road alignment exerts an influence on handling stability of a runaway vehicle to a certain extent, as rational designs of the main road alignment play an important role in ensuring that a runaway vehicle enters a truck escape ramp safely. Firstly, forces acting on the runaway vehicle on the main road are analysed, and the minimum curve radius value and the corresponding approach angle that can prevent lateral rollover and lateral slip are discussed. Secondly, a simulation software, TruckSim, is used to establish a simulation model of the runaway vehicle and the road, wherein the minimum curve radius value and the corresponding approach angle that can prevent lateral rollover and slip are taken as input parameters of the road model. Finally, the established simulation model of the vehicle and road is used to simulate the influence that three types of main road alignment, i.e. a straight line, a right curve and a left curve, respectively have on the handling stability of the runaway vehicle entering a truck escape ramp.

Alternative arresting system design for truck escape ramps

ABSTRACTEach year road accidents claim numerous lives involving run away trucks unable to stop on steep declines. Various passive arresting systems, commonly known as truck escape ramps, are installed on dangerous highway declines to promote highway safety. Truck escape ramps can be divided into three categories: gravity escape ramps, sand or gravel ramps, and arrestor bed escape ramps. However, none of these solutions can control and/or predict the behaviour of a vehicle during the deceleration process within the truck escape ramp. Secondary accidents such as rolling over or rolling back can occur due to the uncontrollable nature during truck deceleration on the truck escape ramp. Existing rescue solutions for the truck after it is arrested in the truck escape ramp often requires complicated procedures with corresponding high costs to remove the captured vehicle and passengers. This paper presents an alternative vehicle arresting system consisting of variable sized prefabricated deformable units made using cementitious materials. Each deformable unit is an independent block and deforms upon truck tire contact. Consequently, the system generates a predictable force that acts opposite to the vehicle motion direction. Results of a 40-ton heavy-duty truck traveling at a 56 km/hr entry speed without braking are included.

Summary of and Lessons from Domestic and Overseas Setting of Truck Escape Ramp

Setting condition and setting location of truck escape ramps in the USA, New Zealand, South Africa, Britain, Australia and China are analyzed in detail and summarized in this paper, it is found that more comprehensive consideration is made in the USA, and it is considered that the function of quantitative analysis for setting the location of truck escape ramp is limited. Finally, clauses and clause explanations which can be adopted in standards and regulations for domestic transportation industry are formed.

Method of TER Location for High-Grade Highway Based on Fuzzy Rough Set

The location technology of Truck Escape Ramp(TER) is the important guarantee for fully developing the TER actions and ensuring operation safety of heavy vehicles on long-steep downgrade. In order to improve the precision of TER location, this paper thoroughly analyzed the influence factors of TER location from the view of traffic accidents statistical data, road conditions and vehicle status. Expounded the theory of fuzzy rough set. Put forward the method of highway TER location based on fuzzy rough set. Used this method to evaluate the running safety of the unit sections on the long-steep downgrade. Calculated the comprehensive safety index values of sample sections and made ones with high comprehensive safety index values as the candidate sections for TER. Determined the accurate positions of the TER based on comparison of the comprehensive safety index value of adjacent candidate sections. Setting effect shows that the TER position determined by the method are scientific and rational.

Determining Need for and Location of Truck Escape RAMPS

The main objective of this paper is to introduce a systematic approach to determine the need for and location of truck escape ramps (TERs). The approach utilizes variables concerning the design vehicle, the road, and the driver. These variables are included in either a stochastic or deterministic form. Vehicle variables include vehicle type, gross vehicle weight, and brake type. Road variables include the profile (length and steepness of grade), horizontal curvature (cornering speed), and the availability of a brake-check area at the top of the grade. Driver variables include information about the driver's actions at the brake-check area, brake checking, and gear selection. A number of supplementary variables are also included, such as accident history and the presence of objects in the path of a runaway vehicle. The approach also utilizes a number of existing vehicle-road performance models to generate relevant data concerning the descent speed, cornering stability, and brake temperature. The application of the methodology is illustrated with examples from highways in mountainous terrain of Jordan and western Canada. The examples selected are diverse and were chosen to illustrate the generalized nature of the methodology.