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Comment by mrfredward | Hacker News Reader

A major oversight here is rate of acceleration. Every organism and vehicle on earth has the same gravity and similar coefficients of friction to work with, so rates of acceleration have roughly the same cap, but the speeds change by orders of magnitude.

So an ant can go from full speed, to stopped, to full speed in a fraction of a second. A car on the highway will take several seconds to stop, and much longer to smoothly accelerate, leading to standing wave type effects on highways. This is much less likely with people walking, and even less likely with ants.

The dynamics of cars on the highway is governed by the difficulty of changing speed and direction. For ants, this constraint is negligible. So these things don't really compare.

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I also really loved the throwaway about ants not caring about collision.

I can "solve" a lot of traffic problems too, if nobody involved is worried about collisions.

Thats like driving in India in with a three wheeler taxi.

I think that's part of the promise of self-driving cars -- they'll ostensibly be safer, so can drive closer together, and can cooperate at intersections to increase throughput, no one needs to stop, just adjust speed to allow a gap.

Though based on my car's adaptive cruise control ability, we've got a long way to go before we can have cars that drive within a few feet of each other at highway speeds, and even longer before we could have intersections without signals (or stops).

I don't know if this promise will ever be real in that extent. Even if you assume perfect drivers(automatic or not) with instant reaction speed there can be situations where a road can become impassable quickly due to external influences, and this alone makes short distances between cars unsafe.

All it takes is one rock dropping onto the road heavy enough to immediately stop a car in its tracks, and what would follow would be a series of collisions affecting a large number of cars.

Then you need to leave gaps for new arrivals from a different road, and in the end I don't think the efficiency would be that much higher.

Presumably autonamous cars would maintain proper separation - I try to maintain a three to five second gap between myself and the next card, but drivers in my area tend to be quite aggresive and will force their way into the gap - I have nearly been hit or run off the road multiple times.

I think the benefits are more that the car strictly obeys road rules, as opposed to humans being unaware, ignoring, or straight up willfully breaking (e.g. speeding) the rules.

<rant>

On my path to and from work there is a "trouble nexus" - you have a few main roads intersecting, a relatively short stretch of road with a couple of entrance/exits towards a public transit hub (trains, buses, and a large carpark converging - so there's a lot of road traffic), then a bridge, then another major intersection and exits onto a highway.

People are always slowing down to create a gap in the traffic flow and let vehicles from the transit hub onto the road leading up to the bridge, in an effort to be kind towards other drivers, but this has disastrous effects on the traffic behind it - interrupting the traffic flow of the major roads.

If people did not make space for vehicles from the side roads, the main flow of traffic would pass fairly quickly and then the sideroad traffic would be able to get on noramlly.

</rant>

The point I am trying to make is that autonamous cars would let traffic planners adjust e.g. road speeds, traffic light timings, etc. closer to a global optimum without having to account for human selfishness.

Also ants can walk over each other in heavy-traffic areas. Would be a game-changer for highway congestion.

Eh, I feel like that's a rather small factor compared to the main reason we experience traffic jams (tragedy of the commons) and ants do not:

>"Traffic jams are ubiquitous in human society where individuals are pursuing their own personal objective," the authors explain. "In contrast, ants share a common goal: the survival of the colony, thus they are expected to act cooperatively to optimise food return."

If everyone drove 40mph during rush hour, we'd be well within capacity even with increased drivership. When everyone tries to go 65+mph, that's when things slow down to 5mph. Prisoner's dilemma here, not the limits of acceleration.

Hmmm, this is the best justification I've heard to replace cars with bionic ants.

And to replace humans with tiny, ant-sized humanoids?

I've wondered the same thing about the effect of slow-accelerating trucks on stop-and-go bay area freeway traffic during rush hours. I feel that the effects are fairly non-linear as more of these vehicles are introduced. Some cities in India don't allow heavy vehicle traffic on congested roads during peak commute hours, though I'm not sure if there's been a study of traffic patterns that validates/simulates these scenarios.

Pretty sure Bay Area Traffic is only negligibly affected by big trucks. It’s, in my experience because they have these ridiculous bottleneck merges (a two lane merge, plus that ridiculous diamond lane, merging into a single lane on the destination highway. It’s like a Venturi. Then there are “exit only” signs designating a lane that isn’t exit only. The 101 south just before the 85 has this problem: you think it’s exit only but it isn’t.

Just some bad highway design. Also places like the Embarcadero interchange at the 101 in Palo Alto has existing traffic fighting with entering traffic within 200 meters of space. HOV lanes make it even worse because you end up squeezing all the lanes and you create incentives for HOV drivers to merge all the way to the left as quickly as possible which further delays the main lanes since people are getting slowed down from the lane changes. Then, when HOV drivers have to exit, again they have to merge all the way right again. There is a bottleneck squeeze and the lateral squeeze happening as well. Houston traffic by comparison is “bad” but far better than the Silicon Valley version despite Silicon Valley having a smaller population and fewer cars.

I used to wonder about this often, and many years ago wrote simulations to model traffic. The introduction of connected on/off ramps were the main cause of congestion due to acceleration, merging, etc.

Exit before/ merge after we much better than exit after/merge before. SV has many of these congestion building ramp strategies.

I think another consequence of that is that collisions have zero cost.

Momentum v strength doesn't scale linearly.

Ant foot traffic and human foot traffic are probably comparable. Human highway traffic might need to be compared to rat highway traffic.

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