Site A scores 7.5 and site B 6.7. Move 20 points of weight to roads and B wins, 7.5 to 6.7.

A suitability model ranks every cell for one purpose. You cannot add degrees, class codes and meters, so each layer is first reclassified onto a common 1-9 scale. Then each scale value is multiplied by its percent influence and the results are added. The weights are a choice, and they can move the answer across a valley.