Semi-trailer Truck Research Articles

Education and outreach for the International Polar Year

If the 65 educators, scientists, and media specialists who gathered at the “Bridging the Poles” workshop in Washington, D.C. last June have their way a semitrailer truck labeled “Got Snow?” would traverse the country during the International Polar Year (IPY) of 2007–2009 loaded with polar gear, interactive activities, and a snowmaker.We would significantly increase the number of Arctic residents—especially indigenous Alaskans—with Ph.D.s. We would build exchange programs between inner city youths and polar residents. Polar exhibitions would open at natural history and art museums and zoos. And polar postage stamps, interactive polar computer games, national polar book‐of‐the‐month recommendations, made‐for‐TV polar documentaries, and a polar youth forum would bring the poles front and center to the public's attention.

Toll Network Capacity Calculator: Operations Management and Assessment Tool for Toll Network Operators

A performance assessment tool was developed to assist managers and operators of highway networks containing toll collection facilities. The toll network capacity calculator (TNCC) quantifies a toll facility’s ability to process traffic. The calculator can also help engineers who are designing toll facilities to serve highway systems adequately. TNCC determines the maximum amount of traffic that a collection facility can handle. In addition, TNCC may be used for disruption management during lane closings, incidents, or maintenance checks. Furthermore, TNCC may be employed as a planning tool and a performance assessment tool by predicting the impact of surging traffic volumes during special events. The performance of a toll facility was determined from plaza characteristics such as lane number, lane type, and processing rates. The results of the calculations met constraints set by the characteristics of the arriving traffic. For example, variables such as the percentage of arrivals that were electronic toll collection (ETC) patrons and the percentage of arrivals that were semitrailer trucks requiring non-ETC services influenced the plazas’ performance outcome. Overflow of ETC users from the dedicated ETC lanes into the mixed lanes was also a factor. Performance was independent of hourly arrival volumes. Videotapes and transaction data at plazas provided necessary input to TNCC in the evaluation of 32 plazas on the toll network of highways in Orange County, Florida.

Postmortem Blood and Vitreous Humor Ethanol Concentrations in a Victim of a Fatal Motor Vehicle Crash

A 20-year-old male was found on the passenger side of a small car after a collision with a semi-trailer truck. Postmortem blood, collected from the chest cavity, and vitreous humor samples were collected following harvesting of the heart and bones. Gas chromatographic analysis revealed a blood ethanol concentration of 0.32 g/dL and a vitreous humor ethanol concentration of 0.09 g/dL. The stomach was intact and full of fluid and food, but its contents were not collected. Possible explanations for the large difference between the two results include diffusion of ethanol from the stomach into the chest cavity, contamination of the blood sample prior to collection, and ingestion of a large quantity of ethanol shortly before death. This case demonstrates the importance of proper quality assurance procedures in collecting postmortem specimens and of collecting a vitreous humor sample for ethanol analysis in postmortem toxicology cases.

Content of Variable Message Signs and On-Line Driver Behavior

Variable message signs (VMS) are programmable traffic control devices that convey nonpersonalized real-time information on network traffic conditions to drivers encountering them. Especially useful under incidents, VMS aim to influence driver routing decisions to enhance network performance. This study investigates the effect of different message contents on driver response under VMS. Presumably, if the message content is a significant factor in driver response, the traffic controller can use it as a control variable to influence network traffic conditions positively without compromising the integrity of information. This issue is addressed through an on-site stated preference user survey. Logit models are developed for drivers’ diversion decisions. The analysis suggests that content in terms of the level of detail of relevant information significantly affects drivers’ willingness to divert. Other significant factors include socio-economic characteristics, network spatial knowledge, and confidence in the displayed information. Results also indicate differences in the response attitudes of semitrailer truck drivers compared to other travelers. They provide substantive insights for the design and operation of VMS-based information systems.

Impact of 44 000-kg (97,000-lb) Six-Axle Semitrailer Trucks on Bridges on Rural and Urban U.S. Interstate System

The impact of a 44 000-kg (97,000-lb) tridem semitrailer truck on bridges on the urban and rural U.S. Interstate system is examined. The impacts are determined using a suite of models developed for FHWA policy use, and both agency and user costs are estimated. Bridges on the Interstate system that are already deficient at current loads are excluded from this analysis, which utilizes the National Bridge Inventory database and reports results for the rural and urban Interstate systems.

Truck Traffic Crossing Texas–Mexico Border

U.S.-Mexico trade continues to grow strongly, with much of the non-petroleum surface trade moving by truck. Trade flows through a number of key ports-of-entry at the southern border, and future truck traffic has raised concerns over infrastructure needs, congestion, and safety. Although it was known that Mexican trucks are frequently overloaded, little data were available to show whether this extended to trade movements at the border. This paper reports the results of a research study commissioned by the Texas Department of Transportation and represents the first comprehensive analysis of truck axle loads undertaken at the southern Texas border. Weigh-in-motion systems were installed at the Laredo and El Paso ports-of-entry. WIM data for 1995 show that 25 percent (El Paso) and 35 percent (Laredo) of the observed tandem-axle loads on loaded northbound five-axle trucks (three-axle tractor with tandem-axle semi-trailer) exceeded the U.S. limit (15.4 Mg). This truck type comprised about 80 percent at El Paso and 70 percent at Laredo of all observed weekday northbound border-crossing trucks. In 1995, 80 percent at El Paso and 87 percent at Laredo of the observed tridem-axle loads on loaded six-axle (three-axle tractor with tridem-axle semi-trailer) trucks exceeded the U.S. limit (19 Mg). This truck type, however, typically comprised only 43 trucks per weekday (3 percent of loaded trucks) at Laredo and 13 (2 percent) at El Paso. The occurrence of overloads on tridem axles was reduced substantially at one port-of-entry when the Texas Department of Public Safety temporarily applied enforcement activities in the Customs yard at the Laredo port-of-entry. The WIM technologies worked well under unusual conditions and indicated that they can possibly be used to aid enforcement of size and weight regulations when the next phase of the North American Free Trade Agreement is implemented.

Calibrating WIM Systems Through AVI Technology

This paper describes a method for calibrating weigh-in-motion (WIM) systems by comparing static and dynamic weights of vehicles through automatic vehicle identification (AVI). The AVI facilities developed for the Heavy Vehicle Electronic License Plate (HELP) project on the 1-5 corridor was used for this purpose. The static axle load of AVI-equipped vehicles was obtained from the Oregon DOT for two sites, WIM load data from in-service 5-axle semitrailer trucks was obtained on the 1-5 corridor over a 6-month period. The data was analyzed to sort-out AVI numbers, dates and times of weighing. Errors were calculated as the percent difference between WIM and static loads for individual axles/axle groups. Calibration factors were derived to set the mean axle weigh error to zero. Software was written to handle all calculations.

Calibration of Weigh-in-Motion Systems Through Dynamic Vehicle Simulation

Abstract This paper describes two methods for calibrating weigh-in-motion (WIM) systems with the aid of dynamic vehicle simulations. A modified version of the vehicle simulation model VESYM, named VESYMF, is used for predicting the dynamic axle load variation exerted by heavy vehicles at a WIM site. The first method uses test trucks performing controlled runs over a WIM system, while the second method relies on the consistent properties of the steering axle loads of traffic stream 5-axle tractor semi-trailer trucks such as the 3-S2. For the first method, test truck runs are performed at a number of replicate speeds and the WIM measurements of individual axles are plotted versus speed. For a given axle and speed, the variation in WIM measurements is equal to the precision of the WIM system. Combining this source of variation with the dynamics-induced variation calculated through VESYMF, gives the anticipated frequency distribution in WIM measurements for the pavement roughness at a site. This is used for estimating the probability of a particular WIM measurement, which in turn allows the calculation of the weighed average of the axle load WIM measurements obtained at different speeds. Calibration is effected by fitting a zero-intercept linear regression equation between the static and the average WIM axle load measurements. The second method is based on the consistent properties exhibited by the mean load of the steering axles of traffic-stream 3-S2 trucks. Its combined variance is calculated by adding the variance in static 3-S2 steering axle loads for traffic-stream vehicles to the other two components of variance described previously. This establishes a confidence interval for the mean of the WIM measurements of a number of 3-S2 steering axle loads. The feasibility of these two methods was demonstrated by field experimentation.

Field Verification of Moving Load Model for Pavement Response

A validation study undertaken to verify the predictive capability of a recently developed moving load model to predict pavement response is described. The full-scale field-measured responses of longitudinal strain at the bottom of the asphalt concrete (AC) layer were used in the verification. The field testing program, in which the strain responses induced by a semitrailer truck were measured as a function of vehicle speed, was carried out at the Pennsylvania State University test track. The material behavior of the AC layer, which was assumed to be viscoelastic, was deduced from the laboratory behavior of the AC and from the backcal culated AC modulus from falling-weight deflectometer data. The unbound material layer properties were assumed to be elastic. The moving load model reproduced many important general observations made from the field tests, such as the existence of a complex interaction in the case of a tandem axle configuration and the strong influence of vehicle speed on the strain response. G...

Field Verification of Moving Load Model for Pavement Response

A validation study undertaken to verify the predictive capability of a recently developed moving load model to predict pavement response is described. The full-scale field-measured responses of longitudinal strain at the bottom of the asphalt concrete (AC) layer were used in the verification. The field testing program, in which the strain responses induced by a semitrailer truck were measured as a function of vehicle speed, was carried out at the Pennsylvania State University test track. The material behavior of the AC layer, which was assumed to be viscoelastic, was deduced from the laboratory behavior of the AC and from the backcalculated AC modulus from falling-weight deflectometer data. The unbound material layer properties were assumed to be elastic. The moving load model reproduced many important general observations made from the field tests, such as the existence of a complex interaction in the case of a tandem axle configuration and the strong influence of vehicle speed on the strain response. Good agreement exists between the predictions made by the model for the strain response for single and tandem axle configurations under different loading and vehicle speeds and those measured in the field. The difference is less than 14 percent, thus verifying the applicability of the moving load model to predict pavement response.

Weigh-in-Motion Data Quality Assurance Based on 3-S2 Steering Axle Load Analysis

An innovative method is offered for conducting the quality assurance of weigh-in-motion (WIM) data by analyzing the variation in the measurements of five-axle semitrailer (3-S2) truck steering-axle loads. Confidence-interval limits for those measurements are established on the basis of their historic mean static loads adjusted for the effect of air resistance and their combined variation from two sources, the variation within a fleet of 3-S2 trucks and the variation due to axle dynamics at a WIM site. The first variation was determined by analyzing historic 3-S2 load data obtained by FHWA using static scales. The second variation was established through dynamic vehicle simulations of a typical 3-S2 truck using vehicle model VESYM and the roughness profile at a particular WIM site. The method was tested with data from four WIM systems in the state of Washington, two bending-plate systems and two piezoelectric systems. The proposed method resulted in clear indications of the performance of the scale versu...

Weigh-in-Motion Data Quality Assurance Based on 3-S2 Steering Axle Load Analysis

An innovative method is offered for conducting the quality assurance of weigh-in-motion (WIM) data by analyzing the variation in the measurements of five-axle semitrailer (3-S2) truck steering-axle loads. Confidence-interval limits for those measurements are established on the basis of their historic mean static loads adjusted for the effect of air resistance and their combined variation from two sources, the variation within a fleet of 3-S2 trucks and the variation due to axle dynamics at a WIM site. The first variation was determined by analyzing historic 3-S2 load data obtained by FHWA using static scales. The second variation was established through dynamic vehicle simulations of a “typical” 3-S2 truck using vehicle model VESYM and the roughness profile at a particular WIM site. The method was tested with data from four WIM systems in the state of Washington, two bending-plate systems and two piezoelectric systems. The proposed method resulted in clear indications of the performance of the scale versus time by the number of confidence interval violations observed.

A mixed-integer linear model for optimal processing and transport of secondary materials

In every area of materials recovery management, transportation is an important component of waste management systems. Affordable transportation methods to move material from seller to buyer should be carefully investigated. The current study examines the possibility of installing intermediate processing stations between sellers and buyers. Intermediate processing stations are needed to assure quality of the recycled paper and cardboard and to collect and densify these materials for economical transport by truck or rail. The approach used emphasizes the application of a mixed-integer linear programming model for transportation of recovered paper. The research was focused on expressing the transportation optimization problem as a linear programming problem. Determination of optimal locations for the processing stations is emphasized. For this study, the available modes of transportation to recycling markets included semi-trailer truck and rail. The computerized transportation model presented is a general model applicable to either mode and can be modified to evaluate relevant secondary materials. The result of this research is an optimal transportation system model for the movement of recovered paper from selected sources in the State of Iowa to anticipated markets within the state. In most cases, truck transportation is the most practical mode because of its flexibility in routing and unit hauling capacity.

Calcul des émissions unitaires de polluants des véhicules utilitaires

To assess pollutant unit emissions for duty vehicles we combine engine emission maps with engine operating conditions as calculated by a vehicle simulation model. The SIVA model takes into account the vehicle characteristics (engine, transmission, etc.) including load, and the characteristics of the route taken (road gradients and curves, speed limits, stops). This model calculates instantaneous operating conditions, in particular the engine torque and speed which in turn enables the calculation of pollutant emissions. CO2, CO, HC, NOx and particulate emissions as well as fuel consumption were calculated for three duty vehicles, a small 3.5-tonnes duty vehicle, a 19-tonnes truck and a 40-tonnes semi-trailer truck. Simulated operating conditions corresponded to highway (a 65-km trip), main road (a 93-km trip) and steady vehicle speed conditions for various values of road gradient from −4% to +6%. Results show the significant influence of vehicle mass on fuel consumption and pollutant emissions, engine technology (injection, aspiration), engine tuning (legislation, regulation), vehicle speed and road gradient. Collecting data on pollutant emissions and data on operating conditions in actual vehicle use are thus of great interest.

Evaluation of piezoelectric weigh-in-motion system

The analysis presented deals with the accuracy of a piezoelectric weigh-in-motion system installed on Interstate 19 in the state of Oregon. Axle weights for 5-axle tractor semi-trailer trucks were measured by the piezoelectric weigh-in-motion system and then compared with the static weights. An analysis of variance and Dunnett's test were conducted in order to determine if there existed a significant difference between data. The analysis showed no significant difference for steering axle and tandem axle weights. However, the analysis did indicate that a significant difference existed for trailing tandem. Key words: weigh-in-motion, dynamic weight, static weight, highways, piezoelectric weigh-in-motion.

Predicting Vertical Acceleration in Vehicles through Road Roughness

This study investigated the use and suitability of the International Roughness Index (IRI) for predicting vertical acceleration in truck shipments at recommended highway speeds. The investigation resulted in the development of a mathematical procedure for predicting the expected power‐spectral‐density (PSD) vertical acceleration at a specific location on the truck bed as a function of IRI, pavement type and age, dynamic characteristics of the vehicle, and speed of travel. The data for this study were collected from 20 different sections of highway pavements using two devices: a profilometer, which recorded elevation profiles of the pavement sections, and an accelerometer, which measured the vertical acceleration in the rear of a tractor semitrailer truck bed traveling at one of three different speeds. A major result of this study is procedure for estimating the PSD vertical acceleration in the rear of the truck bed for selected pavement categories and truck speeds using only the pavement IRI and the vehic...

Dynamical behavior of a tractor-semitrailer combination near the boundary of the domain of stability

A distinctive feature of rubber-tired tractor--trailer trucks ("automotive trains") is the capability of relative rotation of the tractor and trailer(s). This feature increases the maneuverability of the combination vehicle in comparison with a single truck of the same length and thereby decreases the turning radius of the vehicle without skidding or wheel detachment. However, combination vehicles suffer a loss of stability of straight-ahead motion, and an increase in the number of trailers diminishes the possibilities of analytical investigation, because each additional trailer in the case of rubber-tired vehicles adds at least one new degree of freedom to the vehicle. The only exception is the case of perfectly rigid wheels, which create the classical condition of nonholonomic constraints: The number of degrees of freedom of such a vehicular combination in planeparallel motion is equal to two, now matter how many trailers are pulled. The first studies of the dynamical behavior of a tractor-semitrailer combination was aimed at ensuring the stability of straight-ahead motion. In cases that are not Lyapunov critical, the problem is known to be solved on the basis of a linearized approximation of the equations of perturbed motion. The practical significance of the problem has stimulated a great many relevant investigations in our own and other countries. Its solution currently encompasses results of a general nature (e.g., an expression tbr the critical velocity and turning radius of a combination with an arbitrary number of trailers [5]) and results pertaining to semitrailer and double-trailer trucks [6, 7]. In particular, the boundaries of the stability domain have been established in the space of parameters of a tractor--semitrailer pair [6]. These boundaries correspond to a simple zero eigenvalue or a pair of nonmultiple, purely imaginary eigenvalues of a matrix of equations in variations when all other eigenvalues have negative real parts. Cases of multiple roots of the characteristic equation have not been observed, i.e., the investigated real linear system is decomposed into a direct product of oneand two-dimensional systems. The dynamical behavior of the system near a stability boundary depends on the type of stability of the boundary [4]. The present article is devoted to the solution of this problem and a discussion of the implications of the solution in regard to a tractor--semitrailer combination. We note that the flutter--divergence bifurcations of a tractor--semitrailer in the vicinity of a point in parameter space where the characteristic equation has one zero root and a pair of purely imaginary roots have been analyzed previously in a series of papers [12-t5]. The mathematically related problem of the vibrations of a double pendulum bui!t-in at one end and loaded by a nonconservative following force has also been investigated [10, 11].

Applications of state-of-the-art technology in vehicle data collection

This paper discusses recent developments in the technology of vehicle load and traffic volume data collection and proposes methods for their application. Applications focus on innovative methods for calculating equivalent axle load (EAL) data. The first part of the study contains an example output of the state-of-the-art vehicle monitoring equipment. Typical output of weigh-in-motion scales (WIM), vehicle classifiers, and vehicle monitors are presented to demonstrate the potential of the new technology. In the second part of the study, WIM scale data covering a period of 1 year is analyzed to explore new methods for collecting EAL data. It is shown that, in terms of daily data, EAL repetitions correlate better with the volume of large vehicles (e.g., 5-axle semitrailer trucks) than with the total number of axle counts traditionally collected. Furthermore, the notion of using vehicle length to index broad vehicle classes is explored as a means of obtaining volume counts of the large vehicles. It is concluded that data obtained by vehicle monitors can indeed be used successfully to identify broad vehicle groups. Key words: weigh-in-motion, vehicle classifiers, vehicle monitors, vehicle length.

Nonlinear Truck Ride Analysis

The nonlinear vibratory motions of a three-axle semitrailer truck were investigated via the use of a digital computer. The nonlinear equations of motion are presented and a method of numerical integration is discussed. The analysis allows any shape of suspension force-deflection curve (including wheel hop, suspension stops, and dry friction damping) and a similar liberality of shock absorber force-velocity characteristics. An experimental vibration study, performed on a model truck, is described and the results compare favorably with the calculated results of the numerical integration.

Seat-Belt Fractures of the Spine and Sternum

IN A RECENT ISSUE of the Journal, Howland et al¹reviewed automobile crash injuries attributed to improperly positioned, lap-type seat belts and reported the first case of an unusual transverse fracture of a lumbar vertebra sustained by acute flexion of the torso over the lap belt. A similar "fulcrum fracture" of the lumbar spine is described in case 1 below. The implication has been that seat-belt injuries may be prevented by proper positioning of the laptype belt or by the use of the "bandolier" or shoulder-type belt. That the latter type of safety harness also is capable of producing skeletal injury is indicated by case 2. <h3>Report of Cases</h3><h3>Case 1.—</h3> A 21-year-old woman was admitted to the emergency room immediately after injury in an automobile accident. The patient had been a passenger in a small, foreign sports car which had struck the rear of a semitrailer truck while