No big problem in a motor vehicle. 40kmp is no great speed and we have gradients worse than that in Devon . No way would I do that ,in my youth ,on a bicycle. The safety margin between cyclists and motor vehicles is not wide enough especially with the air vortex as a HGV or Bus passes close by.
Whilst it does look a little perilous (possible because of the camera angle), I'd be more wary of crossing this bridge on a foggy morning in the autumn:
The Sheppey Crossing is not that much different to the Japanese effort. It is about the same length and 35m high compared to 44m for the Japanese bridge.