The side road (aka tertiary) will no longer be able to send traffic onto the main highway or be able to run straight across the main highway. Southbound will have to take that small cutoff, head north then do a U-turn. Northbound has to turn a block shy of the intersection and then turn left at the traffic signal. The main road will be prevented from doing anything onto the side road other than a soft branch in the same direction (i.e. north-bound to north-bound and south-bound to south-bound). Hope this makes it more clear.