Squeezing safety margins : How does the design of roads affect road safety and how do societal changes affect the design of roads?

The report discusses whether simultaneous changes in several of the safety margins built into roads can have greater effects than the sum of the effects of each change (interactive effects). It is concluded that interactive effects are likely to be present, reducing more than one safety margin may have greater effects than the sum of the individual effects of the changes. The report also discusses whether societal trends imply that design standards for roads can be different in the future. Finally, the report discusses what the road sector can learn from aviation and rail with respect to simultaneous changes in several safety margins. The road sector may benefit from developing a stringer safety culture, similar to than found in rail and aviation, by following up notification of irregularities even more systematically, and by inspecting infrastructure more frequently.