How does a global transportation system become a robotic transportation system almost overnight?
The answer is clip-on robots.
Robots (and their sensors) that you simply clip onto the driver's seat of the vehicle.
It sees what the driver/pilot/captain would see, both outside and in. It uses the same controls to control the vehicle. It hears the same things.
Simple. Effective. Inexpensive. Fast.
Here's an example of clip-on robot that can ride a motorcycle from Yamaha.
This approach gets around the need to rewire vehicle. Rewiring, as every engineer and mechanic knows makes things difficult. Simply, if you open up the control panel of a vehicle to modify it, the costs of installation go up exponentially and the regulatory burden (testing, certification, authorization) becomes insanely heavy.
It also gets around the problem with replacing existing vehicles with new, specially outfitted vehicles. That will only accelerate once the value of the new transportation system is demonstrated.
NOTE: This is very similar to how the big installed base of PCs were automagically converted "overnight" into Internet computers by simply adding a modem and some software...
This conversion will also be fairly inexpensive. All of the tasks associated with driving, flying and sailing can be accomplished using cameras and microphones. Although useful and increasingly affordable, complex sensors like LiDARs aren't required due to rapid advances in deep learning (Musk and Tesla are betting on this approach).
At the rate things are going, we'll see clip-on driving/flying/sailing systems in the mainstream within a decade Once that happens, the costs, benefits (1,000% safer than self-driving), etc. of these systems will make them ubiquitous soon thereafter.
PS: Clip-ons are asymmetric. For example: Clip-ons could potentially turn any vehicle into a VBIED. They also allow a military that is behind to catch up fast with better funded institutions (think: how wireless phones allowed countries to leapfrog over wired infrastructure).