[laksjd]

That's not really very fast at all. Most cars can easily go faster than that, the only limits are the human drivers and their pesky problems with reacting quickly enough at high speeds. Sure, no car could go that fast in a city but I'd be surprised if people were going to be happy with large amounts of people flying over residential areas so your flying car might be grounded by regulations/etc inside cities anyway.

If you want to make the world smaller than the most cost effective solution might be to enforce a common standard for networked cars and ban human drivers from motorways.

Cars regularly go >125mph (at least on the few bits of German Autobahn that have no speed limits) and while that is an insanely stupid thing to do with human drivers and their awful reaction speeds + their inability to know the intention of other drivers, a 125mph highway could be achieved via networked computer driven cars (and excluding human driving,of course) with significantly less effort than it would take to make flying cars available to anybody but a select few.

[vidarh]

It's not very fast at all if forced to follow roads. It's a big deal if you can fly in a near straight line.

And while, yes, you can drive fast on the autobahn and similar, most of us don't live right next to a freeway and go to/from places directly on a freeway, so the average speed will tend to be far lower.

To take some extreme examples: average traffic speeds in London are below 20mph, with certain congested parts well below that.

We will never get to 125mph+ everywhere on the ground, because car drivers is not the limiting factor, but other factors such as pedestrian safety in residential areas etc.

[saiya-jin]

in fully automated traffic, we can get 2x the current speed, even 3x in congested areas, and probably no traffic jams ever again.

it's not a straight line performance, but considering how 'little' is needed (capable ai-drive) compared to complete overhaul of almost everything just that people can fly around and land somewhere... much more realistic goal

[vidarh]

This assumes the only limit is congestion, which it isn't. E.g. roads near me will soon be 20mph to intentionally make it undesirable to use them for through traffic past peoples houses, and to reduce pedestrian accidents.

In Central London, 3x means maybe reaching 30mph, but increasing parts of Central London are also getting 20mph, and while it might very well be that safer automated cars would make it viable to bring that back up to 30mph, you can't travel in a straight line or anything resembling it in the most central parts of London.

E.g. in the most central part there is a single road covering the city centre East/West (Oxford Street), which is also restricted to taxis and buses (and it's still one of the most congested roads in town). To travel the same distance East/West, you need to drive a substantial distance along heavily congested roads South/North, or drive through a maze of smaller back streets and deal with traffic lights and pedestrians haphazardly crossing all over the place, so actual speed measured by straight line between starting point and destination is a tiny fraction of the driving speed for a lot of locations in the centre... It's not uncommon for it to be faster to walk even when there isn't much congestion, depending on where you are going from/to.

So while there may be plenty of places where being able to fly won't be worth it, there are certainly also locations where "just" 100mph would still beat even automated cars by several times if you don't need to spend time driving somewhere dedicated to take off/land. This latter is the biggest caveat - if your "flying car" is really a "drivable convertible plane" that needs something resembling a runway, a heavily congested city core won't exactly be ideal.

Though saying that, even my old commutes in to London were far slower on average than 100mph when taking the bus + train, despite bus + train beating driving a regular car by a massive margin, and that was between locations with far less congestion than the centre.