Hacker News Reader

Comment by whoisthemachine | Hacker News Reader

> and traffic will get a lot worse once people are ok with sitting in bad traffic and watching Netflix

This one could go either way I think, traffic might actually improve once autonomous driving is the standard.

I also kinda-sorta hope that if autonomous driving takes over, that cars end up gaining the ability to switch onto and off of rails, I think this would be the ideal end-state... people still maintain the ability to move independently of each other but we have the improved safety of transport on rails.

View on HN

I can't find the report, but IIRC there was a study that calculated that autonomous driving could triple the carrying capacity of highways because they could safely reduce following distance. They also estimated fuel/energy savings due to them being able to collectively draft of each other.

Yeah, right, ever seen "following distance" at rush hour in a US city? I've got a higher chance of seeing a unicorn.

In reality, self-driving cars would help by increasing following distance and leaving a genuine gap so people don't crash every goddamn day on the same arterial roads.

You don't even need rails for traffic to improve. Just think at what happens when a traffic light goes green: human drivers slowly, one-by-one, cross the intersection. Whereas a platoon of self-driving cars can, in principle, just accelerate (or brake) simultaneously. On highways this also improves drag/energy efficiency and has already been tested in Europe as part of EU Truck Platooning Challenge.

My only thought was rails truly require little intelligence for autonomy, and require less maintenance (or at least less involved maintenance), but just doing some armchair engineering...

I'm not sure why you think rails are safer than rubber tires. Metal-on-metal contact has way less friction, which makes for much worse stopping distance and worse safety especially at crossings. Having grade-separated dedicated infrastructure _does_ improve safety, especially if there's no human drivers involved, but we can do that just fine with pavement in tunnels or elevated roadways.

Very good points... intuitively, rail seems safer (and simpler to automate?), but your points have changed my mind... Now I wonder though, how do modern roller-coasters stop so suddenly? Magnetic breaks?

Electromagnetic brakes are used, but the biggest difference is that the weight of passengers is a much bigger portion of total weight (you don’t have a locomotive and the cars are not nearly as heavy per passenger) a decelerating quickly is part of the appeal. If passengers on trains were unencumbered with stuff and strapped in as on roller coasters, they could be built to do it too.

Rails are safer because vehciles are more predictable - they are always on the track, with only limited places where they can switch tracks, and you can control that externally ensuring there are no conflicts. Rails can handle more people because in the form of a train they can pack in a lot more people. Cars use a lot of space for engine and luggage compartments.

The thing is the average car lifetime in the US is about 12 years so, so even if you assume autonomous driving "everywhere" is available in 10-20 years, that means you probably don't have a vast majority autonomous fleet for maybe 50 years. It certainly would be politically infeasible for the government to tell people they have to buy new cars.

I agree that the existing car stock will take a decade or two to age out, but I can't see any reason it takes 50 years to get to a majority autonomous fleet. Maintenance costs for cars in autonomous fleet will be significantly lower due to standardization and economies of scale, so non-autonomous cars will look relatively expensive in comparison (beyond being less convenient), causing them to be scrapped sooner than you'd otherwise expect.

I agree, my original post did not imply this transition would happen quickly, I think transitioning to automated vehicles will rely more on society changing, so at least one generation from the youngest today... and as far as requiring people to get automated cars, if they're safe enough, it will be like outlawing drunk driving, ie you're infringing on others right to live if you don't use an autonomous vehicle. The corollary is that right now there should be laws strictly controlling the use of autonomous vehicles.

OK. I read your comment as saying that it would happen slowly, not quickly, which is what I was disagreeing with. Personally I think the economic advantages of routinely using a self-driving taxi service will drive most people to simply not buy a new car when their old one wears out, and that this will happen many years before human-driven cars are outlawed (or, more likely for a while, regulated/taxed very heavily without being completely illegal).

Like crappy little trains with no capacity?

Magic little trains that can take you from and to anywhere.

Reply on news.ycombinator.com