Security is critical to transport systems as they are often appealing targets for terrorist attacks. The significant costs of potential damage make effective security policies a key concern for transport decision makers. This Round Table examines the contribution economic analysis can make to improving security. The analysis covers the impact of uncertainty in assessing security policies and on the cost effectiveness of security measures in aviation and maritime shipping. Much can be criticised in current policies, which are often seen as unduly expensive and inadequately assessed. This Round Table identifies methods for quantifying the benefits of security measures and assessing their effectiveness, and examines techniques to allocate resources to targeting the highest risks. Applying these techniques would achieve better levels of security with current resources.