Hi !
Sorry for the late reply, I've been in holidays.
If you select a street node, you have the option to change the default 'Crossing' connection to a 'Junction' in the Inspector.
Though sadly, the Dynamic City Layout tools currently still are limited. Especially specific On- and Off-Ramp connections are not yet possible to define as precise as you'd need.
We're working on the Street System, but this specific with will take some more time !