The importance of flow composition in real-time crash prediction

•We analyze the impact of having access to flow composition data for crash prediction.•We built SVM and logistic regression models using aggregated and disaggregated data by vehicle type.•The results show that the use of disaggregated data could improve the prediction power up to 30 %.•These results may be useful to evaluate technology investments in expressways. Previous real-time crash prediction models have scarcely used data disaggregated by vehicle type such as light, heavy and motorcycles. Thus, little effort has been made to quantify the impact of flow composition variables as crash precursors. We analyze the advantages of having access to this data by analyzing two scenarios, namely, with aggregated and disaggregated data. For each case, we build Logistics Regressions and Support Vector Machines models to predict accidents in a major urban expressway in Santiago, Chile. Our results show that having access to disaggregated data by vehicle type increases the prediction power up to 30 % providing, at the same time, much better intuition about the actual traffic conditions that may lead to accidents. These results may be useful when evaluating technology investments and developments in urban freeways.