Q Issues related to runway incursions are measured using a metric system also known as the SSM. SSM stands for the Surface Safety Metric and aims at identifying the greatest risks related to runway incursions. Previously used metric systems judged the concept of runway incursions based on the severity and numbers of runway incursions. But in case of this metric, the environmental issues related to a runway are assessed. This system also assesses the outcome of events such as damage to the aircraft, fatalities and injuries as well based on advanced forms of modelling