Adam: Marking road edges with reflecting posts gives drivers a clear view of the edges, thereby enabling them to drive more safely  Ttherefore, marking road edges with reflecting posts will decrease the annual number of road accidents
Aiesha: You seem to forget that drivers exceed the speed limit more frequently and drive close to the road edge more frequently on roads that are marked with reflecting posts than on similar roads without posts, and those are driving behaviors that cause road accidents
raising a consideration that challenges the argument's assumption that facilitating safe driving will result in safer driving