This paper analyzes the safety benefits of the implementation of PathProx, a runway incursion alerting system. Airport surface incursions have been identified by the National Transportation Safety Board (NTSB) as one of the most significant safety hazards in civil aviation. PathProx is a system development by Rannoch Corporation to help address this problem. It is an aircraft-based runway incursion alerting system, providing runway incursion alerts directly to the pilot(s) in the cockpit. PathProx has undergone a series of simulator and flight tests conducted by NASA over the last 3 years. It is part of the NASA Runway Incursion Prevention System (RIPS). These tests have validated the basic concept and design of PathProx. Several analyses have been performed related to the safety benefits of PathProx implementation. These include analysed of critical runway incursion scenarios and Monte Carlo simulation. The Monte Carlo simulation results indicated that the risk of collisions due to runway incursions could be nearly eliminated through aircraft equipage with PathProx. The simulations and analyses also found that PathProx provides significant improvement in runway safety even without full fleet equipage-where only of the two aircraft involved in a conflict is equipped. Analyses have also been done to compare the safety improvements provided by PathProx with that provided by ground system surveillance and alerting. PathProx provides more timely alerting than provided by ground-based systems, primarily by eliminating the delays associated with having the controller in the loop and associated communications delay.