Many highway bridges carry traffic in two same-direction lanes, and modeling thetraffic loading on such bridges has been the subject of numerous studies. Differentassumptions have been used to model multiple-presence loading events, particularlythose featuring one truck in each lane. Using a database of weigh-in-motionmeasurements collected at two European sites for over 1 million trucks, this paperexamines the relationships between adjacent vehicles in both lanes in terms of vehicleweights, speeds and inter-vehicle gaps. It is shown that there are various patterns ofcorrelation, some of which are significant for bridge loading. A novel approach to theMonte Carlo simulation of such traffic is presented which is relatively simple to apply.This is a form of smoothed bootstrap in which kernel functions are used to addrandomness to measured traffic scenarios. It is shown that it gives a better fit to themeasured data than models which assume no correlation. Results are presented fromlong-run simulations of traffic using the different models and these show thatcorrelation may account for an increase of up to 8% in lifetime maximum loading.
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