In order to reach a suitable height for the ships, a steep incline is needed to get the cars high up enough before crossing the river which causes the bridge to acquire a terrifying image:
This type of structure is absolutely terrifying, and I know that I would not feel happy having to drive up this type of incline!
The bridge is beautifully designed, and though the slope looks extremely steep in these pictures, the engineers were able to design it with a max slope of 6.1 percent, which is pretty good. This means that for every 100 feet of horizontal distance the bridge extends, it rises 6.1 feet. This may seem like a minuscule number, but in the field it is quite a respectable slope!