Transport-related environmental problems continue to constitute a major challenge to policy makers at all levels. A key feature of these problems is that they arise from the interaction of human behavioral systems and physical systems. Thus, to improve our understanding of environmental and health problems associated with vehicle emissions it is necessary to combine data on both travel and traffic behavior with environmental data linked to the corresponding spatial and temporal variables. There are currently no such databases available. A new low-cost real-time device is currently under development utilizing the latest developments in environmental monitoring, navigation, communications, data mining and warehousing to capture spatio-temporally referenced data on vehicle and driver performance and the level of emissions and concentrations. Because of the need to acquire data in all environments, there are potential limitations in using a global satellite navigation system such as GPS to determine the spatial and temporal data in built-up areas. Therefore, an augmentation strategy involving differential GPS and new low-cost dead reckoning sensors utilizing micro-electromechanical systems technology has been explored. This paper presents a high-level description of the real-time vehicle performance and emissions monitoring system, and details the results of a study carried out to characterize the performance of stand-alone and augmented GPS, and assess whether the required navigation performance is achievable. The study characterized the performance of different types of stand-alone GPS receivers and GPS augmented with differential infrastructure and low-cost dead reckoning sensors. The performance indicators used were satellite visibility, coverage, accuracy and integrity. The results highlight the weaknesses and differences in performance, depending on the type of GPS receiver used and shows that, unlike GPS alone, an integrated system employing GPS and low-cost dead reckoning sensors is capable of meeting the required navigation performance in built-up areas. Furthermore, no significant difference in accuracy between standalone GPS and differential GPS has been seen.
In the past decade interest has focused on the remote analysis of emissions from motor vehicles using spectrometric techniques, driven by recognition of the fact that a very large proportion of the environmental damage done in this way originates with a small percentage of vehicles. Several instrumentation manufacturers now market such devices, and others are developing new technologies that will offer opportunities for enhanced performance and lower cost.In this paper we review the evolution of technologies and methodologies applied to motor vehicle exhaust emissions, ranging from simple broadband sources and band-pass filters to tunable diode laser absorption spectroscopy. In so doing we examine the compromises and sources of error inherent in each which have earned such devices a very variable reputation, at least in the early years of development. We also look at techniques that may have the potential to solve these problem, and critically examine the reasons why these have not (yet) been applied.In conclusion, we will present initial findings and results from a European consortium studying the problems of costeffective emissions monitoring, and validation of emissions inventory data using complementary numerical modelling techniques.
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