That's a good point - I didn't think about network effects of having autonomous cars communicate with each other. No doubt it will boost safety, but I strongly suspect that such technology will be heavily regulated and standardised. If Boeing and Airbus each developed a mid-air collision avoidance system, wouldn't regulators force them to interoperate?

Of course there will still be an autonomous car company with a superior safety record and perhaps better navigation routing, but these are not strong advantages. Consider that budget airlines can compete effectively with established airlines even when they have a worse safety record and fewer direct routes.