Having taken a non black cab yesterday which involved the driver reprogramming the sat-nav, whilst talking on his Bluetooth and handing my friend a business card, I'm OK with relying on human knowledge once in a while.

You chose to take a non-black-cab, right?

I may not have all the facts, but I think it's fine for the black cabs to offer a luxury service that you need to pass a hard test to join. This is distinct from making it illegal for someone else to offer an inferior service at a discounted price.

Ha. I'd be interested to see anyone manage that.

On top of this, in central London it's pretty built up so SatNav doesn't always work in the canyons between buildings.

I don't know - some modern satnav systems are able to get hold of live traffic info and suchlike. That was always the point of The Knowledge - to know (for example) which major thoroughfares to avoid so you aren't going to be sitting in gridlock for an hour, however counterintuitive such evasive manoeuvres might be to an automated route finder.

The better informed the satnav, the less valuable that is.

Plus a SatNav won't know that at rush hour, a longer (distance-wise) route could be quicker in a black cab due to them being allowed to use bus lanes.

I don't want to say "that should be easy to do," but I'd be shell-shocked if any company with experience doing navigation systems couldn't figure this out without too much trouble.

Also, even if GPS signals are hard to get in London, navigation in a fixed city can be calculated in lots of different ways. Allowing for some regulatory limits, a company (or an experienced third-party) could scatter their own transmitters around the city as needed, figuring out which frequencies give the best accuracy.

It should be easy to minimize turns across traffic and avoid traffic lights... but they seem to have plenty of trouble doing that.

Google maps already integrates with Uber. If they managed to get such connection, I'm not sure why a bigger black cab company operating in large cities couldn't get an agreement to include taxi/bus lanes on a separate app. Can't imagine Uber forced Google to cooperate with them...

Google Ventures are an Uber investor, I'm not sure if that's what sparked the integration but it probably didn't hurt!

I'm not sure if there's actually a comprehensive source for bus lane data - if there is, it would be really useful for motorbike users too (who can generally use bus lanes).

Isn't Google -- through Google Ventures -- a significant investor in Uber? That kind of may give them a different set of considerations than "a bigger black cab company" would have.

Sure and I think we're in agreement - Google proved it will do something nice for a taxi company if they profit from it. It's just a very specific kind of profit in this case.

Well, that's a simple software problem with street definitions. Much simpler to fix than what amounts to implementing a GPS/pathfinding system inside someone's head for even one driver.

Works fine with Google Maps for me, even in blackwall tunnel. I think there is some inertial navigation through device accelerometers as well.

For the purpose of my and other people's safety, I don't want my taxi driver to be constantly looking at the phone at the busiest junctions, neither do I want to explain to them how to spell a given street name so that they can type it in their phone in the middle of a busy street during the rush hour.

Maybe in 2024.

It's not "constantly looking at the phone", it's the plain old "using navigation in your car" that many people already do. AFAIK, safe driving with navigation is a long-solved problem.

Source?

Simpy by sheer logic the very act of using a navigation aid (phone, Sat Nav, map) must result in decreased attention to the mechanical process of driving.

I would challenge that safe navigation is a long solved problem.

Who solved it? How? How was it measured? When was it solved - 2013? 2004?