An-Najah Staff

In traffic characterization, axle load spectra (ALS) are one of the most critical inputs in the new Mechanistic-Empirical Pavement Design Guide (MEPDG). Axle load spectra have a significant effect on predicted pavement performance and, thus, the design life. Typically, axle load spectra as measured by weigh-in-motion (WIM) systems are assumed to have adequate data quality and accuracy. In fact, the quality of WIM-based data has inherent uncertainties attributable to inaccuracy and systematic bias. Whereas WIM data accuracy depends on the sensor technology, calibration errors and drift over time may introduce a systematic bias. This technical note investigates the effect of axle load measurement bias on pavement design for flexible and rigid pavements. The results show that negative bias in axle load measurements significantly affects cracking performance for both pavement types. The bias is more critical for rigid pavements with thinner slabs. Therefore, a measurement bias limit of less than ±5% should be required to ensure that both flexible and rigid pavements have adequate design reliability against cracking. That the WIM scales be calibrated periodically to prevent a high negative bias is strongly recommended.

East Lansing, Michigan, is home to Michigan State University and about 40,000 students that bus, walk, and drive cars on campus. Although most intersections are controlled by two-way stop signs or signals, three major intersections are controlled by traffic circles. A study was initiated to address operational problems at one of the six major intersections. The purpose of the study was to determine the feasibility of changing right-of-way control and to evaluate alternatives to the existing traffic circles. Results indicate that accidents (vehicle, bicycle, and pedestrian) at traffic circles were less severe and less frequent. Data also showed that measures of effectiveness, such as fuel consumption, delay times, and emissions, were more efficent at the traffic circles. Overall, the capacity and operation of all the two-way stop intersections could be improved by converting them to traffic circles.