Browsing by Subject "automobiles"

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    Estimated validity and reliability of on-board diagnostics for older vehicles: comparison with remote sensing observations
    (2011-09) Supnithadnaporn, Anupit; Noonan, Douglas S.; Samoylov, Alexander; Rodgers, Michael O.
    Based on requirements under the Clean Air Act Amendments of 1990, most state vehicle inspection and maintenance (I/M) programs have, since 2002, replaced the tailpipe emission testing with the on-board diagnostic (OBD) II testing for 1996 model and newer vehicles. This test relies on the OBD II system to give the pass or fail result, depending on certain conditions that might cause the vehicle to emit pollution 1.5 times higher than the regulated standard. The OBD II system is a computer and sensors installed in the vehicle to monitor the emission control units and signal if there is any malfunction. As a vehicle ages, its engine, pollution control units, and OBD II system deteriorate. Because the OBD II system's durability directly influences the test outcome, it is important to examine the fleetwide trend in the OBD II test results in comparison with an alternative measure of identifying high emitting vehicles. This study investigates whether the validity and reliability of the OBD II test is related to the age of the OBD II system installed in the fleet. Using Atlanta's I/M testing records and remote sensing device (RSD) data collected during 2002-2005, this research establishes the convergent validity and interobserver reliability criteria for the OBD II test based on on-road emissions measured by RSDs. The study results show that older vehicles exhibit significantly lower RSD-OBD II outcome agreement than newer vehicles. This suggests that the validity and reliability of the OBD II test may decline in the older vehicle fleets. Explanations and possible confounding factors for these findings are discussed.
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    Testing an urban myth: do spiders really “love” the smell of gasoline?
    (Office of the Vice Chancellor for Research, 2016-04-08) Schmalhofer, Victoria R.; Reineke, Patrick; Roslender, Chris
    ABSTRACT. Presence of yellow sac spiders (genus Cheiracanthium) in the emissions control (EVAP) system of certain automobiles has prompted recalls because silk blockage of EVAP hoses could lead to cracked gas tanks, fuel leakage, and fire. According to a Reuters report during the 2011 Mazda6 recall, an innate attraction to the odor of gasoline explained sac spider presence in cars (gasoline attraction hypothesis). The media perpetuated this idea to such a degree that it attained the status of an urban myth – even the Wikipedia article for Cheiracanthium discusses the supposed attraction. Alternative possibilities to explain spider presence in EVAP hoses were largely ignored. Car hoses provide just one of many suitable retreat sites available to spiders, so occasional occupation of EVAP hoses may be due more to chance than design (random occupancy hypothesis). It is also possible that EVAP hoses themselves attract the spiders (hose attraction hypothesis). In this study, we tested the gasoline attraction and hose attraction hypotheses. Using juvenile Cheiracanthium mildei, a species known to occupy EVAP hoses, we found no evidence to support the gasoline attraction hypothesis: in both arena tests and Y-tube choice experiments, spiders spent similar amounts of time in control (no gasoline odor) and treatment (gasoline odor present) areas. In contrast, data supported the hose attraction hypothesis. Younger juvenile C. mildei spent significantly more time on the treatment side of the test arena (pieces of hose present) compared to the control side of the arena (no hose pieces present), and younger juveniles were found more frequently on the treatment side of the arena 30 minutes (100%) and 12+ hours (89%) after release into the arena. Interestingly, the clear preference for EVAP hose displayed by younger juveniles was not seen in older juveniles.