[Ohtrahddis]

Because this would likely require a large change in city infrastructure.

Who will be building this? Who will pay for it? If it is the city how will you convince the city's taxpayers to pay for it? If it is a profit-seeking corporation, how will you convince a city to let you cause the disruption, construction, etc. to let you do this?

For other cars, what advantage does this bring to other car manufacturers and why would they agree to cooperate with competitors? Of course there is the obvious benefit that this would help all the players, but why does that marginal benefit outweigh the risk of commoditizing a brand new market / product and eliminating the chance to establish a market share lead. I am partly raising these hypothetical questions because I think companies are trying to "tough it out" and do it without such changes to city infrastructure first and see how that turns out.

I appreciate your simple approach, but you might be disregarding the societal and business factors in favor of making the engineering challenge simpler.

Edit: grammar

[tim333]

Also GPS tracking systems are only accurate to about 20m, not enough to avoid hitting stuff. And transmit over the cell network so don't work if you can't get signal.

[zimpenfish]

Although if you're going to be adding to infrastructure, you could just as well add differential GPS transmitters around the place and get the accuracy down to sub-1m[1] although that's still not really safe enough for cars...

[1] (and I believe you can get it down to ~3cm if you have enough data.)

[dgregd]

Let's say your car ROMB received info about the white truck, while your car cameras and vision recognition systems see just a cloud and any truck in 100 m range.

ROMB purpose is not to replace cameras or LIDARs, but to extend gathered info.