Here is an idea: The 101 from the Olive Mill Road Exit to the Padaro Lane Exit right after Summerland should be in “The Funnel,” a super tunnel for cars only with speeds strictly enforced (with cameras) at 45 mph with no lane changing. Like the Golden Gate Bridge, the traffic lanes will be for commuters. All lanes in the morning would be for going north; from noon to 2 a.m. all lanes would be for going south. There would be no exits except at both ends. Breakdown lanes would line both sides of the three-lane road inside (lit by solar LEDs): The Funnel.
The existing 101 would be unaffected while the Funnel tunnel was being built, except the speed limit would be reduced. The connection at Olive Mill Road Bridge would be widened by one lane in each direction north of the overpass to make room for local traffic and trucks to bypass the tunnel opening — likewise at the south opening.
There are tunneling machines standing by, and the ground is not solid rock, so it will proceed quickly. There will be limited disruption to folks while the holes are being dug and lined with reinforced concrete. Start in the middle and go in both directions simultaneously. Easy, faster for less money.
Go for it, S.B.! Happy Motoring.