United States Department of Transportation
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Lateral vehicle accelerations due to longitudinally tined portland cement concrete pavement.
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2009-12-01
[PDF-2.72 MB]
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Abstract:The objective of this study was to determine, via field measurements, the vibration characteristics of vehicle squirming (a.k.a. groove wander) – a phenomenon whereby vehicles experience lateral vibrations due to interaction between tire tread grooves and longitudinal pavement grooves. The report documents the details of a literature review of groove wander related studies as well as the results of field testing performed to measure vehicle and vehicle occupant vibrations during wander behavior. Recommendations are made about the development of a wander evaluation system for future Colorado Department of Transportation (CDOT) studies. Field testing was performed over two days on a 4.8km (3mi) stretch of I-70 between E-470 and SH 36 Airport Road using a 2000 GMC Safari cargo van belonging to CDOT and known to experience wander. Lateral accelerations were measured at several locations including the seat frame, seat cushion, seat back, and the passenger’s head. Wander is measurable as a low-frequency, low-amplitude phenomenon. Typical wander behavior is observed in the frequency band 1-3Hz. The most effective sensor location to capture vibrations due to vehicle wander proved to be the passenger’s head. This location takes advantage of the human body’s amplifying and filtering characteristics. For the testing conducted here with acceleration measured on the passenger’s head, wander was generally associated with acceleration peaks greater than 0.75 m/s² (0.076g); however, vibration magnitudes are dependent on many factors including sensor location, vehicle, tire type, and vehicle occupant characteristics and posture. The standard methods for evaluating human exposure to vehicle vibrations (ISO-2631) did not yield a reliable indication of wander. Given that other sources of lateral vibration (e.g., wind, bumps, steering input) can lead to similar acceleration behavior to that of wander, and the fact that vibration amplitudes are dependent on many factors, it remains important to have human input when performing wander assessment. Given the difficulty in reliably and consistently quantifying wander, CDOT should consider relying solely on human assessment. If the goal is to determine whether or not wander exists for a certain stretch of roadway, human judgment appears accurate and reliable, i.e., the existence or non-existence of wander is clear and obvious to a passenger. If it remains desirable to develop a standard method to measure and quantify wander (e.g., to compare different roadways or tining patterns), the following should be kept in mind: Wander is vehicle-specific, so any efforts to standardize wander measurement need to employ a consistent, specific vehicle; The best location to place an accelerometer to capture vehicle wander is the passenger’s head; Since vibrations are subject and posture dependent, subjects (or possibly an anthropomorphic test dummy) need to be similar in size and filtering characteristics, and given specific instructions regarding posture.
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