The 'Self Drive' Act puts America on the road to reducing congestion

I know a few traffic engineers and one of the things they regularly laugh about are zipper merge advocates (as well as traffic circle advocates, but that's a discussion for another time). It's not that they don't recommend the zipper merge, it's that the advocates think they are magical and ascribe magical effects to them that don't exist in reality.

Want an example of the perfect zipper merge? Look at an hourglass. Thousands of tiny grains of sand perfectly zipper merging at the last instant. And yet there is still a traffic jam. Inflows and outflows still dominate traffic congestion. Now imagine what would happen if you early merged those grains of sand. Your hourglass is now 6 miles tall. Interestingly enough, the early merge is more efficient for flow, but not by enough of a margin (1-2%) to overcome the drawback of the terrible space efficiency.

What the zipper merge is really good at isn't improving flow, it is improving space efficiency. The bottleneck uses far less of the highway when people merge last instant. This allows people to reroute or exit the highway before the traffic jam, reducing the burden on the bottleneck. That's it, nothing more. The idea that traffic would suddenly get so much better if people zipper merged perfectly is not rooted in reality...traffic volume is still the more important factor by several fold.

It is possible the reduced need for downtown parking could significantly reduce congestion in cities though.

Public infrastructure should not be a la carte.

Thing bigger, friend.

(Truth be told, I'm from quite the opposite land where driving taxes finance much of the public spending. I wouldn't really mind your proposition too much.)

No they can't, not if you want them to be safe. The biggest problem we have with human drivers, most people will say, is that humans can't drive safely. And one of the biggest reasons that is is because we drive way too close to each other. In an urban environment, it is practically impossible to maintain safe following distance: someone will slip in and take that spot instead.

Sure you might say that they can communicate with each other--they can't, not in any reasonably close timeframe for infrastructure (say, the next 30 years) where cars have to assume that human drivers are still on the road.

A worse effect is that self-driving cars are more likely to strictly stick to rules of the road and safe driving than humans are: so longer following distances, slower speeds, strict right-of-way rules when trying to make a left onto a jammed road... I don't see how they're going to be better.

This is fantasy land. This idea has been perpetuated by a few layman websites and extremely simplistic closed-loop simulations, but have never been validated by the more sophisticated traffic simulation systems used by traffic engineers. In fact, quite the opposite.

Bad reaction times contribute to waves, but waves are just annoying and feel like the cause of congestion to the driver. According to the traffic engineers I know:

1) You can't ever fully get rid of traffic waves because reaction time is only a fraction of the speed mismatch correction problem, physics still dominates.

2) You can't ever fully get rid of speed mismatches. Even a plastic bag flying on the roadway is enough to cause them.

3) Traffic waves only feel like congestion to those who experience them first hand. Minimizing traffic waves doesn't decrease travel times significantly, it merely moves congestion to harder bottlenecks like traffic signals, highway on and off ramps, or merge points.

4) Braess' paradox only manifests itself when agents are acting rationally. As rationality increases, whether through better mapping and routing systems like Waze or by algorithmic rationality of SDCs, more bottlenecks appear that didn't previously manifest themselves under a lower rationality state. Unless you can somehow centrally control SDCs (which is unlikely IMO), this will only become more prevalent.

But if you put twice, or worse 5x, as many cars on the freeways, that'll just jam up the urban core even worse than it already is. And self-driving cars are probably less efficient than human-driven cars in the urban core simply because they're much less aggressive in their interactions with pedestrians and cyclists. This is a good thing, but it will increase congestion.

Efficiency improvements can only add increase capacity by a fixed percentage. The massive improvements in cost ($0 in labour!) and convenience will cause usage to increase by orders of magnitude, IMO.

BTW, I suspect that the bigger impact of self-driving cars would actually be the reduced need for parking space.

Touching your brakes to flash your brake lights when braking with your engine isn't an altogether bad idea on congested road with traffic waves – it's a good signal to the car behind that you're slowing down (before they can actually see that) so that you can together help mitigate the propagation of the wave.

After my car drives me 45 minutes to work it still needs to park nearby to pick me up after work.

Everybody loves the idea of new technology that allows them to continue doing what they are doing, in this case avoiding biking, walking, and public transit. Basically, people want to believe self driving cars will reduce congestion. Ergo, it's pretty easy to convince them it will.

http://www.sfchronicle.com/bayarea/nevius/article/More-ride-...

That article provides no evidence to support this claim other than the fact that 37k people have driven for Uber/Lyft/et al in SF. The author then extrapolates that adding 37k drivers to SF is a huge number. As if all those drivers appeared in SF ex nihilo.

Since public transit requires a walking trip at both ends, it will never be very popular in areas where one needs to take a dangerous mile-long walk across a sea of parking and high-speed arterials, instead of a quick jaunt through a lively neighborhood.

https://www.strongtowns.org/journal/2017/8/15/financing-subu...

https://granolashotgun.com/2016/08/31/a-thousand-hidden-subs...

https://www.strongtowns.org/journal/2017/1/8/a-utah-republic...

https://www.strongtowns.org/journal/2017/1/18/highway-spendi...

https://en.wikipedia.org/wiki/SkyTran

It seems like there's always a "we're going to try it here" phase, then it never goes further.

The upsides sound great - basically personalized mass-transit, using individual pods on an overhead track system. The pods and track are lightweight, and can likely be put into tighter routes and areas than a full-sized train can go, as well as not disrupting traffic or whatnot when it is installed.

It does have the whole "monorail" stigma to get around (which I don't really understand why or how "monorails" got the stigma - they have issues, certainly - but the whole meme seems to only have started since that Simpsons episode)...

I suspect people with cars are still very protective of their ability to completely control their schedule; agreeing to ride in someone else's car makes it difficult to run errands after work without first stopping at home to pick up the car, for example. And what if they have a ride scheduled for 5pm but find out at 3pm that they need to stay later? With enough scale it shouldn't be hard to find an alternate ride, but we're not to the point where people can expect that to be easy.

I think people could definitely rearrange their lives a bit to make this better, like planning to run errands on weekends, or close to home (instead of work). Or setting reasonable boundaries with their employer (I'm scheduled to leave at 5pm, and not a minute after -- unless you want to pick up the tab for a taxi). But people are selfish, and stuck in their ways, and would, for some reason, prefer to sit in traffic.

yes it does: http://i.imgur.com/RDHyKBh.gif

I would say even the minimal change of funding 2x as frequent trains on BART would do wonders for making it more useful. Unfortunately residents in the bay area have way too much say in what does and doesn't get built, so new stops and new lines are difficult, to say the least.

Down the road, you can start to relax the preemption (theoretically) and let the market forces keep unwise state regulation in check.

But it also means that they only need to meet one standard, not 50. Which sounds like the right thing to do when it comes to regulating something mobile that will operate in all 50 states.

Where else are we going to live?