Weigh Station Research Articles

Illegal Weigh Station Bypassing

Illegal Weigh Station Bypassing

A deep convolutional neural network based approach for vehicle classification using large-scale GPS trajectory data

Transportation agencies are starting to leverage increasingly-available GPS trajectory data to support their analyses and decision making. While this type of mobility data adds significant value to various analyses, one challenge that persists is lack of information about the types of vehicles that performed the recorded trips, which clearly limits the value of trajectory data in transportation system analysis. To overcome this limitation of trajectory data, a deep Convolutional Neural Network for Vehicle Classification (CNN-VC) is proposed to identify the vehicle’s class from its trajectory. This paper proposes a novel representation of GPS trajectories, which is not only compatible with deep learning models, but also captures both vehicle-motion characteristics and roadway features. To this end, an open source navigation system is also exploited to obtain more accurate information on travel time and distance between GPS coordinates. Before delving into training the CNN-VC model, an efficient programmatic strategy is also designed to label large-scale GPS trajectories by means of vehicle information obtained through Virtual Weigh Station records. Our experimental results reveal that the proposed CNN-VC model consistently outperforms both classical machine learning algorithms and other deep learning baseline methods. From a practical perspective, the CNN-VC model allows us to label raw GPS trajectories with vehicle classes, thereby enriching the data and enabling more comprehensive transportation studies such as derivation of vehicle class-specific origin-destination tables that can be used for planning.

Weigh Station Impact on Truck Travel Time Reliability: Results and Findings from a Field Study and a Simulation Experiment

Weigh stations are necessary for safeguarding highway infrastructure by enforcing truck weight limits. However, mandating all trucks to stop at all weigh stations decreases travel time reliability. This decrease in travel time reliability adversely impacts the productivity of the trucking industry and to a lesser degree impacts personal travel reliability as well. This study, conducted at the Lumberton weigh station on Interstate 95 in North Carolina, quantifies the impact of weigh stations on truck travel time reliability. Truck travel times were observed over periods of weigh station operation and weigh station closure. Comparison of these two states sheds light on the variability in travel time caused by weigh station operation. Results show that when the weigh station is operational, truck travel time reliability degrades significantly. VISSIM microsimulation software was used to quantify the expected impact of weigh in motion (WIM) on truck travel time reliability assuming different scenarios of WIM truck bypass. The model results indicate that WIM technology does increase travel time reliability and provides benefits to both trucking companies and enforcement agencies. It was also found that increases in the proportion of WIM bypass result in increases in route travel time reliability. However, this simulation model improvement was not uniform, with the highest marginal improvement occurring in the 30%–40% WIM bypass range.

Adaptive weigh-in-motion algorithms for truck weight enforcement

Weigh stations are the primary weight compliance checkpoints for commercial trucks. In the past decades, states have deployed weigh-in-motion (WIM) technology to reduce delay and increase weight violation enforcement. However, due to limitations on the accuracy and implementation of WIM technology the full potential of WIM has not been realized. To this end, this paper presents an adaptive algorithm that improves the efficiency of WIM-equipped weigh stations based on real-time weigh station queue length, truck demand, weight distribution, and static scale service time. Instead of using one fixed weight threshold value, our proposed floating-threshold control algorithm increases the threshold value based on the queue length at the weigh station to avoid station closure while still identifying the worst weight offenders: the threshold value is lowered when the queue is short to maximize the number of inspection. We develop the queueing models for both the fixed-threshold algorithm and the floating threshold algorithm and derive their mathematical formula to calculate the measures of effectiveness of a weigh system. A simulation model is developed to compare the performance of the proposed adaptive algorithm with a traditional fixed-threshold algorithm under various situations. The simulation results show that an adaptive algorithm yields higher violator capture percentage, lower station closure frequency, and less delay to non-violating trucks.

Operation Analysis of the Electronic Screening System at a Commercial Vehicle Weigh Station

Electronic screening (e-screening) sorts and diverts commercial vehicles that have a high likelihood of being overweight into a weigh station using weigh-in-motion technology. E-screening is known to add significant efficiency in operating weigh stations by allowing eligible trucks to bypass the in-station inspection, hence reducing the congestion at the weigh station. The primary goal of this study was twofold: (a) to develop a simulation model for describing the e-screening operation at truck weigh stations and (b) to analyze and evaluate the weigh station operation with varying values of affecting factors including the transponder penetration rate and the weigh-in-motion weight threshold. This study focuses the e-screening operation at a small weigh station with relatively short queuing area and heavy truck volumes, which is inevitably vulnerable to truck overflows and is sensitive to the prevailing transponder penetration rate and the weigh-in-motion threshold. The simulation results reveal that an e-screening operation can substantially improve the overweight enforcement and can reduce the travel time of legal trucks passing the test weigh station. The simulation results also demonstrate that properly adjusted weigh-in-motion thresholds can effectively enhance the overweight enforcement by preventing overweight trucks from being granted a false green light as a result of the erroneous weigh-in-motion measurement error. The study results also indicate that with the transponder penetration rate equal to or less than 20%, the e-screening benefits are relatively insignificant and adjusting the weigh-in-motion threshold may further deteriorate the enforcement efficiency.

Field Evaluation of Truck Weigh Station Operations

Weigh-in-Motion (WIM) systems can improve the capacity of weigh-station operations by screening trucks traveling at high speeds and requiring only trucks within a threshold of a maximum permissible weight or axle load to be weighed on more accurate static scales. The efficiency of a weigh station is highly dependent on the accuracy of the WIM screening system. This article examines the operations at the Stephens City weigh station in Virginia. The case study evaluates the accuracy of the WIM technology, in addition to the operations of the weigh station, in terms of service time (time that the truck is on static scale), queued delay, and system time. Specifically, the study demonstrated that the WIM systems did not conform to American Society for Testing and Materials (ASTM) standards for Type III WIM systems. The study also demonstrated that by incorporating a weight threshold of 96% only 16% of the trucks that were identified as possible violators actually violated the legal limits. Consequently, 84% of the trucks that were required to enter the static scale were forced to incur unnecessary delays and caused additional delays for violating and nonviolating trucks.

Evaluation of Applicability of Ultrathin Whitetopping in Florida

A three-dimensional (3-D) finite element model for stress analysis of pavements with ultrathin whitetopping (UTW) under critical loading conditions was developed. The 3-D model developed was used to analyze the UTW test pavement sections at the Ellaville Weigh Station in Florida, which had less than satisfactory performance. The poorly performing UTW sections at the Ellaville Weigh Station were found to have relatively higher maximum computed stresses under critical loading conditions, which appeared to explain their poor performance and high percentages of cracked slabs. The 3-D model developed was also used to perform a parametric analysis to determine the effects of asphalt thickness, asphalt modulus, concrete thickness, concrete modulus, base stiffness, subgrade stiffness, slab dimension, temperature differential in the concrete, and applied load on the maximum stresses in UTW pavements under typical Florida conditions.

Weigh-in-Motion Applications for Intelligent Transportation Systems-Commercial Vehicle Operations: Evaluation Using WESTA

An investigation was undertaken to sort the efficiencies of different types of weigh-in-motion (WIM) systems commonly used for enforcement of commercial vehicle operations. Weigh station microsimulation model WESTA (WEigh STAtion) was used. The investigation focused, in particular, on the effect WIM system accuracy has on the effectiveness of presorting commercial vehicles before they approach a weigh station. WESTA simulations were performed, with and without mainline WIM, on a typical commercial weigh station facility across a range of commercial truck volumes (200, 400, and 600 Class 9 trucks per hour) and WIM system accuracies (ASTM Type III and Type I WIM). Three evaluation criteria were used: ( a) number of compliant trucks required to report to the station, ( b) number of overweight trucks instructed to bypass the station, and ( c) time the weigh station remained open. It was found that weight enforcement efficiency improved with WIM. The improvements in efficiency translate into considerable savings for both the weight enforcement agency in relation to improved enforcement effectiveness and protection of the infrastructure and for the trucking industry in relation to reduced user-delay costs. It was also found that higher WIM system accuracy results in higher agency and user savings.

Truck Travel Time Around Weigh Stations: Effects of Weigh in Motion and Automatic Vehicle Identification Systems

Weigh in motion (WIM) technology may provide an efficient and cost-effective complement to static weighing. An evaluation of the effectiveness of an automated bypass system around a weigh station in Illinois is presented. The system combines the use of automatic vehicle identification (AVI), high-speed weigh in motion (HSWIM), and low-speed weigh in motion (LSWIM) technologies to facilitate preclearance for trucks at the weigh station. The preinstallation conditions were compared with post-installation conditions of WIM/AVI so that the effects and benefits of the system could be evaluated. During preinstallation, average delay was 4.9 min/truck, and 7 percent of trucks had delays of more than 10 min. The station was intermittently closed to prevent the truck queue from backing up onto the Interstate highway, allowing 15 to 51 percent of trucks to bypass the station without being weighed. In postinstallation, the delay for trucks equipped with transponder and allowed to bypass on the freeway was reduced by 4.17 min. The delay for trucks equipped with transponders and allowed to bypass inside the weigh station was reduced by 2.02 min. The delay for trucks that reported to the weigh station decreased by 1.25 min. On the other hand, less than 1 percent of trucks that have been observed in after-study were able to bypass on the freeway. With greater numbers of trucks being checked, fewer trucks on the road may exceed the allowable weight limits. Consequently, electronic screening minimizes road deterioration and risks to public safety and levels the playing field for illegally operating carriers and carriers who operate in compliance with the law.

Evaluation of weigh-in-motion in Manitoba

The primary objective of a weigh-in-motion (WIM) system is to provide highway designers and agencies with information on the loads and traffic volumes using a particular highway, thereby facilitating improved pavement design, management, and weight enforcement. In this paper, the historic performance of WIM systems in Manitoba is evaluated. The results indicate that large numbers of unreasonable data are produced from the WIM systems, calibration procedures are not standardized, and there is drift in calibration. The performance of the Brokenhead WIM system was evaluated through a detailed survey conducted at the Brokenhead WIM site and the Westhawk Permanent Truck Weigh Station in August 1997. The Brokenhead site is on the Trans-Canada highway east of Winnipeg. It is the only WIM system in the country that measures truck characteristics and movements between eastern and western Canada. The survey produced a large database permitting the comparison of truck dimension measurements, truck weights, and vehicle classification between those produced by the WIM system and those observed manually. The results indicate that WIM axle-spacing data sets were outside the tolerance for 95% conformity specified by the American Society for Testing and Materials (ASTM). The system classified 5 to 9 axle combination trucks more accurately than some 2- and 3-axle vehicles. The WIM system underestimated about 90% of truck weights in the survey period. The degree of underestimation exceeded 50% of the corresponding static weights. This finding highlights the importance of quality control and corrections on WIM data prior to their use in research or engineering practice.Key words: weigh-in-motion, vehicle classification, calibration, axle spacing, axle load.

Accident Reduction Effects of Using Weigh-in-Motion and Automatic Vehicle Identification for Mainline Bypass Around Truck Weigh Stations

Using weigh-in-motion (WIM) and automatic vehicle identification (AVI) technologies may permit trucks with appropriate credentials to bypass the weigh station on the mainline traffic stream. This would reduce the number of disruptions to the mainline traffic stream and reduce the chances that an accident might occur. Characteristics of accidents on road segments around weigh stations [influence zones (IZs)] are examined and compared with those for accidents on similar basic freeway sections [control zones (CZs)]. There were significantly more accidents around weigh stations than on similar basic freeway sections, particularly during operating hours. Similarly, there were significantly more accidents involving trucks in the IZs than in the CZs. A comparison of the number of IZ and CZ accidents during typical operating hours, excluding animal-related accidents, indicated that the CZs had 38 percent fewer accidents than the IZs. This would result in 146 fewer accidents during typical operating hours around the 20 Interstate weigh stations when animal accidents are not included. When animal accidents were included, the reduction was 30 percent. This would reduce the total number of accidents during typical operating hours around the 20 Interstate weigh stations over 10 years by 129. Thus, a maximum reduction of 129 to 146 accidents could be achieved if the IZs were made identical to the CZs. These figures represent the upper limit of accident reductions. A model is developed to predict potential accident reductions around weigh stations at varying levels of WIM and AVI usage. The resulting model is an S-shaped curve, which should approximate the potential accident reductions as a function of percent WIM-AVI usage.

Truck Delay and Traffic Conflicts Around Weigh Stations: A Case Study in Illinois

Truck weight enforcement helps protect infrastructure and improve traffic safety. However, requiring all trucks to stop at all weigh stations reduces productivity and increases enforcement costs. This pilot study was conducted at the Williamsville weigh station in Springfield, Ill., to quantify the delay and traffic conflicts experienced by trucks around weigh stations. The quantification is needed to evaluate the effectiveness of automatic vehicle identification/weigh in motion (AVI/WIM) systems for electronic screening of trucks at weigh stations. The main emphasis of this project is to examine potential benefits of intelligent transportation system (ITS) technologies for intrastate commercial vehicle operations (CVO) applications. Reducing the number of traffic conflict incidents due to the merging and diverging movements of trucks would increase traffic safety. In the case study, without the AVI/WIM system, on the average, 30 percent of all trucks could not be weighed because the weigh station was temporarily closed to prevent a queue backup. The average delay was 4.95 min/truck and varied from 3.56 to 6.59 min/truck. The maximum delay varied from 8.69 to 137.62 min/truck. There were significant numbers of conflicts even under light-volume conditions. Models to predict the number of conflicts were developed. The number of diverge conflicts depends on car and truck volumes, and the number of merge conflicts depends on the truck volume on the ramp and the car volume in the right and middle lanes of a six-lane interstate.

Rehabilitation of Ellaville Weigh Station with Ultrathin Whitetopping

The Florida Department of Transportation constructed the first ultrathin whitetopping (UTW) project at the Ellaville truck weigh station on I-10 in northwest Florida. This rehabilitation project included the placement of UTW on the existing asphalt pavement, which had experienced severe rutting problems. Layer thicknesses for the UTW were 80 mm and 100 mm. The joint spacings for the UTW panels were 1.2 m and 1.6 m. High early strength concrete was used in this project. Polypropylene fibers were included in the concrete for the sections on the west side of the weight platform and plain concrete was used on the east sections. The joints on the east section were sealed with silicone sealant and the joints on the west section were left unsealed. Falling weight deflectometer tests and frequent condition surveys were performed on the projects. After 1 year of service and 1.1 million equivalent single-axle loads, the UTW shows good performance. Success and long-term performance of the UTW is highly dependent on the degree of bonding between the UTW and the asphalt base. During the study period, panels 1.2 m2 and 1.6 m2, concrete with and without fibers, sealed and unsealed joints, showed similar performance. It is predicted that the 1-year performance of the UTW at the weigh station is equivalent to 4.5 years of service at a medium traffic intersection.

Simulation Modeling of Electronic Screening at Weigh Stations

Electronic screening of trucks before reaching points of regulatory compliance checks (typically, weigh stations) would allow for more efficient use of government resources while reducing travel time for motor carriers. A study was done of the effects of electronic screening on reducing travel time and enhancing productivity of the weigh station using a new simulation model. The model illustrates the impact of electronic screening on motor carrier travel time savings and weigh station productivity assuming various levels of transponder-equipped vehicles. The results indicate that as participation grows, enforcement agencies and participating (transponder-equipped) and nonparticipating trucks all share in the benefits afforded by a more efficient system.