I have a small bug with the bridges

So, the problem is that I can’t put a bridge between two corners in the border of the city.

more details: the bridge is the bronze bridge, the streets are one with trams the other is a simple street, the bridge is 2 blocks long, i want to put the bridge next to the mountain 

the third photo is to show that in another part of the map i put a bridge but in picture 1 they won’t me do that :(

you can answer me in english, italian and spanish 

thank you very much