Enhancing road crash prediction: A comparative study of Machine Learning algorithms and Safety Performance Functions on the Lagos-Ibadan Expressway

Road traffic crash prediction (RTCP) is a critical aspect of transportation safety, enabling the identification of high-risk locations and informing the implementation of proactive measures. This study explores the comparative performance of Machine Learning (ML) algorithms and traditional Safety Performance Functions (SPFs) to predict road traffic crashes along the Lagos-Ibadan Expressway, a major highway in Nigeria known for its high crash rates. To achieve the objective, SPFs estimated using Negative Binomial Regression (NBR) and ML regression models mainly Support Vector Machine (SVM), Random Forest (RF) and Extreme Gradient Boosting (XGBoost) were developed using historical crash data collected from Federal Road Safety Commission (FRSC) of Nigeria for 10years duration between 2014 and 2023, traffic components and geometric design features as input variables. The study's findings indicate that ML algorithms outperform SPFs in terms of predictive accuracy and sensitivity to complex, non-linear relationships among crash-contributing factors with R2 of 0.99, 097 and 0.84 for training and 0.93,0.9 and 0.76 for testing dataset in the three ML models. However, SPFs remain advantageous in interpretation and ease of implementation. The analysis also highlights the importance of feature selection, with variables such as traffic volume, traffic speed, road curvature and pavement width emerging as significant predictors. Furthermore, this study offers insights for policymakers, traffic engineers, and researchers seeking to improve road safety outcomes through data-driven crash prediction methods. The results emphasize the potential of integrating ML techniques with traditional methods to develop hybrid frameworks for enhanced crash prediction and prevention strategies on high-risk roadways.