The available experimental data for the density and viscosity of liquid aluminum and iron have been critically examined with the intention of establishing a density and a viscosity standard. All experimental data have been categorized into primary and secondary data according to the quality of measurement specified by a series of criteria. The proposed standard reference correlations for the density of the aluminum and iron are characterized by standard deviations of 0.65% and 0.77% at the 95% confidence level, respectively. The overall uncertainty in the absolute values of the density is estimated to be one of $\text{±0.7\%}$ for aluminum and 0.8% for iron, which is worse than that of the most optimistic claims but recognizes the unexplained discrepancies between different methods. The standard reference correlations for the viscosity of aluminum and iron are characterized by standard deviations of 13.7% and 5.7% at the 95% confidence level, respectively. The uncertainty in the absolute values of the viscosity of the two metals is thought to be no larger than the scatter between measurements made with different techniques and so can be said to be $\text{±14\%}$ in the case of aluminum and $\text{±6\%}$ in the case of iron.

Environmental context: Trafficked streets are air pollution hot spots where people experience high exposure to hazardous pollutants. Although monitoring networks provide crucial information about measured pollutant levels, the measurements are resource demanding and thus can be performed at only few selected sites. Fast and easily applied street pollution models are therefore necessary tools to provide information about the loadings in streets without measurement activities. We evaluate the Operational Street Pollution Model, one of the most commonly applied models in air pollution management and research worldwide. Traffic emissions constitute a major source of health hazardous air pollution in urban areas. Models describing pollutant levels in urban streets are thus important tools in air pollution management as a supplement to measurements in routine monitoring programmes. A widely used model in this context is the fast and easy to apply Operational Street Pollution Model (OSPM). For almost 20 years, OSPM has been routinely used in many countries for studying traffic pollution, performing analyses of field campaign measurements, studying efficiency of pollution abatement strategies, carrying out exposure assessments and as reference in comparisons to other models. OSPM is generally considered as state-of-the-art in applied street pollution modelling. This paper outlines the most important findings in OSPM validation and application studies in literature. At the end of the paper, future research needs are outlined for traffic air pollution modelling in general but with outset in the research performed with OSPM.