For fragment impact and sympathetic reaction calculations, a variety of empirical and simple 1D-shock models have been developed. Some of these, like the Walker-Wasley or the Cook-Haskins-James model, use a simple critical energy criterion. The empirical Jacobs-Roslund model has a large database and is well-known in the explosive community for performing quick calculations. For ship vulnerability and survivability calculations, TNO developed a toolbox to estimate the probability of a violent event on a ship (or other platform), based on the scenario that a munition storage is hit by e.g. a bullet or fragments from a missile attack. To obtain the proper statistical output, several millions of calculations are required. Because of this, hydrocode calculations cannot be used for this type of application, but a fast and good engineering solution is needed. To obtain a better estimate of the occurrence of Shock-to-Detonation Transition (SDT) for covered explosives and munitions, TNO has developed an improved model which is a combination of the shock wave model at high pressure through a barrier, as described by Cook, Haskins and James, in combination with the expanding shock wave model of Green. With this model, projectile and barrier material variations can be taken into account only using a critical energy fluence parameter Ec , the shock Hugoniots of the involved materials and some other material parameters such as the density. With this model, various projectile materials, such as aluminium, tungsten or steel, or liner materials such as polyurethane layers on warheads and also internal layers such as asphalt, can be taken into account in the calculations. This combined model gives a better fit with the experimental values for munitions response calculations, using the same critical energy fluence values for covered as well as for bare explosives. A comparison with some other models is given as well as a good, simple option for sympathetic reaction mitigation. In this paper the theory that is implemented in the model is explained and results of the calculations for covered explosives and stored munitions will be presented and compared with other models and with experimental results.