The price is extra lanes and then merging of lanes.
Even I made the mistake of requiring underground tunnels at the U-turns that
still require mergings. In fact, you do not need to provide a tunnel or bridge
to do the crossing. Just provide a U-turn into the lane, without crossing the
road.
The U-turn needs room, so extra lanes are required at the turning areas.
U-turns will take up 2 extra lanes, so the straight roads need to be provided with 2 extra
lanes altogether.
At Kota Kinabalu, U-turns are already provided with 2 extra lanes but a
traffic light is still required.
Let the lanes going to the junction be curved so that vehicles need to slow down. Vehicles making U-turns need to cross lanes to turn left, effectively making a right-turn from the junction.
