United States Department of Transportation
i
Assessment of roadway surface conditions using vehicle-intrinsic sensors, phase II.
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2016-06-28
[PDF-2.14 MB]
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TRIS Online Accession Number:1645020
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Abstract:Using onboard vehicle sensors to provide real-time identification of hazardous road surface conditions, such as the presence of ice, will allow drivers to receive warnings to proceed with caution on compromised road sections, thus reducing crash risks. In the near future, Connected and Automated Vehicle technologies may also allow this information to be shared among vehicles so that drivers can plan their trips more efficiently by selecting alternative routes to avoid inclement road weather areas.
The main objective of Phase II of this study was to establish a real-time correlation between certain variables collected by vehicle onboard sensors (e.g., wheel speed and wheel rotational pulse) and roadway surface conditions under several driving scenarios (e.g., different constant speeds and road grades, roadway ice patches, etc.). In Phase I of the study it was hypothesized that the relative difference in tire rotation, between the driven and nondriven (or free-rolling) wheels that results from tire microslip might be used to assess pavement surface condition, and thus, vehicle traction. Traction represents the amount of grip that a tire exhibits while in contact with the pavement surface and influences the vehicle’s steering control and direction stability during driving.
To further investigate the microslip phenomenon, front-, rear-, and all-wheel drive vehicles were tested to determine the relative rotational displacements of driven and nondriven wheels under dry, wet, snowy/slushy, and icy road surface conditions. All vehicles were driven under controlled conditions of constant speed, no braking, and minimal steering over straight pavement sections of different grades and lengths to compare results. Additionally, onboard safety systems, such as traction control or electronic stability control, were monitored during testing sessions as they were considered potential confounding variables when active. Collected data were employed to calculate ratios of distances traveled per unit of time by driven and nondriven wheels in order to distinguish between different pavement surface conditions. The obtained ratios, termed “Traction Indexes” (TI), were an indicator of a specific road condition and/or incline for the respective road sections.
The results of experimentation with multiple test configurations and passes conducted on road conditions ranging from dry to snowy to icy showed small but statistically discernable differences in the TI values. Changes in these observed values when transitioning from dry to icy surfaces were snow-covered. Lower TI values were always obtained for slick surfaces and uphill direction due to the increased relative rotational displacement for the driven versus nondriven wheels. clearly associated with pavement conditions known to yield poor traction, such as wet or
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