Reliability of travel times is an important indicator of the performance of a traffic system. The congestion caused by incidents is an important cause of the unreliability of travel times. Travel time reliability should be incorporated in social cost benefit analyses for infrastructure investments. With an accurate forecast of travel time reliability a well-educated decision of the consequences of infrastructure investments on travel time reliability, can be made. A large number of incidents (car accidents and breakdowns) are simulated in marginal traffic models MIC (marginal incident computation) and MaC (marginal computation). The research shows that it is possible to forecast travel time variability from door to door in case of an incident, with explicit simulation of incidents in a dynamic traffic model within reasonable calculation time. This could be done because of the usage of marginal traffic models, MIC and MaC, reducing the number of calculations needed and therefor the calculation time.