Modelling and assessing the effects of road traffic safety measures

The nature and the effects of improving road traffic safety by infrastructure redesign and Advanced Driver Assistance Systems (ADAS) are different. This makes comparison of such measures difficult, especially because relevant effect data for ADAS are not yet available. To address this issue, a conceptual model is presented for the effects of road traffic safety measures, based on a breakdown in underlying components of road traffic safety (probability and consequence), and five (speed and conflict related) variables that influence these components, and are influenced by traffic safety measures. The model allows estimating relative effects, and together with available data on absolute effects of infrastructure measures, to estimate absolute effects for ADAS based measures. It may in general help to improve insight in the mechanisms between traffic safety measures and their effects. The model is illustrated by a case study concerning rural roads in the Netherlands.