WTI

Evaluation of Low-cost Weigh-in-motion at Armington Junction Weigh Station

Primary Investigator Contact Information

External Project Contact(s)

Report(s)

There are no reports associated with this project.

Project Objective

To evaluate the accuracy, operations and maintenance requirements and relative costs of a new low cost weigh-in-motion system that is less sensitive to the infrastructure in which it is placed. Results if successful, will lead to widespread implementation in rural areas where lower truck traffic volumes

Project Abstract

Efficient weigh station operation has been limited by lengthy static-scale vehicle weighing processes that often cannot keep pace with the local truck demand. When truck demand exceeds facility capacity, weigh station personnel must either close the entrance to the facility until the truck queue dissipates or must subjectively select trucks to be weighed. In either case, the effective capture of overweight vehicles traveling the nation’s highways is compromised. Weigh-in-motion (WIM) systems serve to improve the operational efficiency of weigh stations by automatically identifying and screening trucks that are the most likely to be overweight.Traditional WIM systems rely on an array of vehicle presence sensors utilizing piezo-electric cable, pressure cell, inductance loop, or bending plate technologies. Weigh-in-motion systems can detect wheel loads, axle loads and spacing, and the number of axles. The systems can also determine the vehicle’s speed, wheelbase, lane and direction of travel and the date and time of vehicle passage.The accuracy of these systems is highly dependent on the infrastructure in which it is placed. Traditional installation has required the system housing to be high quality concrete to minimize the dynamic (bounce and flex) effects of the vehicle-infrastructure interaction. This infrastructure requirement has the potential to greatly increase the cost of implementing a WIM system and perhaps limit its use.A more recent WIM system developed by Kistler promises to deliver the same accuracy or better as traditional WIM systems when installed in either asphalt or concrete. This installation option could potentially result in significant cost savings related to WIM implementation and could ultimately lead to more widespread use of WIM systems, particularly in rural environments where relatively lower commercial vehicle volumes may not justify the implementation of more traditional, higher cost WIM systems. The intent of this project is to explore the performance of this new low-cost weigh-in-motion at the Armington Junction Weigh Station.

Task Descriptions

1. Document System Performance
   1. As a third step, WTI will document the contractor’s success in ensuring adequate performance of the low-cost weigh-in-motion (WIM) system from an equipment-related rather than an operational-related perspective. To accomplish this, the performance of the low-cost WIM system at Armington Junction Weigh Station will be directly compared to: (1) national performance standards for WIM systems and (2) the performance of the traditional bending plate WIM system recently implemented at the Lima Weigh Station. System performance can be described in terms of both (1) accuracy and (2) reliability. Accuracy Proven methodologies will be used for guidance to ensure an accurate performance evaluation. Both the American Society for Testing and Materials (ASTM) and the National Cooperative Highway Research Program (NCHRP) provide specifications/guidelines for evaluating the performance of WIM systems (i.e., ASTM E 1318-94 and NCHRP Project 3-39, respectively). The accuracy of WIM systems when recording various factors such as wheel load, axle load, axle-group load, gross vehicle weight, vehicle speed, and axle-spacing and vehicle classification will be investigated and documented at both the Armington Junction and Lima Weigh Stations. Accuracy checks for a carefully defined period of time will be performed periodically during the evaluation period using sound statistical procedures. The frequency of accuracy checks and their duration will be dependent on the truck volumes experienced at the Armington Junction and Lima Weigh Stations. In each case, the WIM data will be directly compared to data collected using an alternate means. Reported axle and gross vehicle weights will likely be checked using static scales or pre-weighed commercial vehicles. Reported speeds will likely be checked using an approved radar gun. Reported volume counts will likely be confirmed using manual observation or video recording. Reported vehicle classification will likely be checked using manual observations or video recording. Confounding factors, such as pavement roughness and environmental conditions, will be documented during each accuracy check. Particular attention will be paid to the effects of more severe, northern climate weather on the performance of these WIM systems. Reliability System performance can be severely hampered by its reliability. If the system encounters frequent "downtime" due to component system failure, the utility of the overall system is compromised. During the evaluation period, Armington Junction and Lima Weigh Station personnel will be asked to carefully log the nature and duration of any system problems. The WIM systems may also allow for some limited self-monitoring. Again, the effects of weather on the performance of these WIM systems will be carefully documented.
2. Produce Final Report
   1. A Draft Report will be produced summarizing the evaluation of low-cost WIM system at the Armington Junction Weigh Station. The report will likely include the following information: Introduction Evaluation Methodology Operational Improvements System Costs and Implementation, Maintenance, and Operational Requirements System Performance Conclusions and Recommendations WTI will submit the Draft Report to MDT and FHWA for review. MDT and FHWA will be given 60 days for review. WTI researchers will be available to answer any questions that MDT representatives may have during the review process. Upon receipt of comments from all involved review participants, WTI researchers will adjust the Draft Report to reflect appropriate changes. If there is disagreement with any of the reviewers’ recommended changes, additional correspondence or communication will take place between the reviewer and WTI researchers until consensus is reached on the changes. Upon review and approval of MDT, the Final Report will be submitted to the printing agency. It is anticipated that 25 copies will be made and distributed to MDT, FHWA and other parties as requested by MDT and FHWA
3. Document System Costs And Implementation, Maintenance And Operational Requirements
   1. The first objective of this project is simply to compare the direct operational improvements gained when moving from manual weighing methods to automatic weighing methods at Armington Junction Weigh Station to determine the benefits to be gained in a rural environment. A second objective of this effort is to determine whether the costs and associated implementation, maintenance and operational requirements of the low-cost weigh-in-motion (WIM) make it a superior product over more traditional WIM systems. Specifically, a direct comparison will be made between the Armington Junction Weigh Station low-cost WIM system and the Lima Weigh Station bending plate WIM system. For both sites, WTI researchers will collect and document information related to the following: system costs disaggregated by equipment costs, installation costs, maintenance costs and operation costs; implementation requirements; maintenance requirements including vendor support; and operational requirements including vendor support and training. Short-term system costs, including the equipment and installation costs, will be solicited from the WIM system vendors and confirmed with the submitted invoices. For longer-term system costs, including the maintenance and operation costs, WTI researchers will again solicit this information from the WIM system vendors but temper these estimates with information collected informally from the Armington Junction and Lima Weigh Station personnel near the completion of this project. The implementation process at the Armington Junction site may be video-recorded for later documentation. Any problems encountered will be documented to ensure that the evaluation of the product is accurate.
4. Document Operational Improvements
   1. Recall that the intent of implementing automatic weigh-in-motion (WIM) systems over traditional static-scale weighing processes is to improve the operational efficiency of the weigh facility. To confirm this improvement in operational efficiency, WTI researchers will document conditions at the Armington Junction Weigh Station both prior to and following the implementation and calibration of the low-cost WIM system by an outside contractor. Specifically, interest will focus on quantifying the operational improvements to be gained in a rural environment. Potential measures of effectiveness may include the following: vehicle processing time, travel time or vehicle delay through the weigh facility, queue length, air pollution emissions, percent of trucks weighed, and violations captured. Researchers will determine appropriate data collection methods and durations that will result in sufficient data for later analysis while remaining within the project budget. When documentation of the baseline conditions takes place, care will be taken to consider outside factors or activities that may confound the measurable benefits of the WIM system. Confounding factors may include system inoperability, staffing changes, roadway geometric changes, adverse weather conditions, or other. In each case, the same data elements collected when documenting baseline conditions will be consistently captured again. Statistically sound methods will be used to determine the significance of operational changes before and after system implementation. This information may be later compared to low-cost WIM system cost information resulting in a benefit to cost ration for low-cost WIM systems in a rural environment. Specific operational improvements resulting from the implementation of a low-cost WIM system will be documented only at the Armington Junction Weigh Station. However, the noted operational improvements at this rural site will be qualitatively (i.e., not statistically) compared to operational improvements noted elsewhere in the country.

Milestones, Dates, Schedule

Student Involvement

True

Relationship to Other Research Projects

False

Technology Transfer Activities

False

Transportation Research Board Keywords

Weigh-in-Motion, Weigh Scales

Partners

Montana