In many road networks all over the world unexpectedly large delays occur as a result of unforeseen disturbances like incidents. Robustness measures can be taken to reduce these costs. In this paper we focus on network structure related robustness measures like adding spare capacity, creating parallel routes that are spread in a balanced way over the network, adding buffers and unbundling. A network design method for designing road networks that are robust against incidents is proposed which is applicable to real sized networks and can be used in practice. The method combines optimization and evaluation models with expert input. An application to a small test network shows the quality and the sensitivity of the method. The design method is also applied to a large realistic network of Amsterdam and surroundings which shows that large improvements in the network performance can be realised with a positive benefit-cost balance.