There is an increasing demand at both the state and federal levels for accurate and cost-effective weigh-in-motion (WIM) systems. These systems are important to monitor traffic flow and for predicting degradation of roadways due to heavy trucks. They also have applications in Homeland Security. Currently available WIM equipment falls primarily into two categories: 1) high accuracy bending plates and load cells, which are expensive and require significant road closure time for installation; and 2)lower accuracy piezoelectric sensor-based WIM systems. Piezoelectric systems are significantly lower in cost and require much less road closure and installation time than the first catagory. However, piezoelectric sensors have an unpredictable and relatively short service life, along with other shortcomings. The success of recent and on-going evaluations of fiber-optic axle sensors by Tennessee, Alabama, Idaho, Oregon DOTs and toll authorities in Illinois, New York and California suggests that, with some modifications, fiber-optic sensors could be successful for WIM applications. Accuracies are anticipated to be better than piezoelectric systems, but costs should be similar.

To investigate the accuracy and reliability of a fiber-optic sensor system for weigh-in-motion. The objectives will be met by conducting a literature search, contacting state partners to coordinate efforts, developing a test plan, conducting laboratory and field tests of proposed system and components, determining signal properties of the sensors, evaluating cost implications of a fiber-optic WIM system, and reporting findings to the sponsoring agencies.

Researchers will evaluate the advantages and disadvantages of fiber-optic technology with respect to cost, ease of installation, pavement damage, calibration, accuracy, maintenance, service life, power supply needs, portability, and other relevant factors. The research will closely scrutinize the signals generated by fiber-optic sensors, evaluate signal consistency and degradation over time, and evaluate other longevity aspects. There is also a need to evaluate one or more electronic interface units and the appropriate presence detectors in addition to testing the fiber-optic sensor itself. Identifying viable presence detection that is reliable and less expensive than inductive loops is an important goal of this research. At least one of the participating states will also investigate the feasibility of alternative sources of energy such as solar and wind power.