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Why driverless cars may mean jams tomorrow

economist.com

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Re: Why driverless cars may mean jams tomorrow

#71

Post by DarqWebster »

tomohawk wrote: post #23

The odds are that self driving cars will stick to the posted speed limit, and that those limits will not be raised. This will reduce the available capacity of many interstate grade roads, as the posted speed is often unsafely low. On the roads around here, the accepted and safe speed is often around 70mph, but the posted speed is often 55mph. https://www.motorists.org/blog/speed-limits-slower-safer/ Additionally, sel…

Slower not meaning safer is because a slower driver among faster drivers causes more lane-changes, which are a less-safe maneuver. Everyone travelling the same speed is the safest scenario, with slower then being safer, as impacts occur with less energy.

If everyone strictly obeyed the posted speed limit and treated it as both a minimum and a maximum speed, as driverless cars would likely aim to do, roads would be safer. The interim state of having both driverless and human-driven cars on the road at the same time is where problems may arise.

Re: Why driverless cars may mean jams tomorrow

#72

Post by alex_duf »

Cthulhu_ wrote: post #60
alex_duf wrote: post #33

Earlier quoted context omitted.

Then there's hope as it's probably cheaper to have buses full of people than individual cars

It already is, but based on the availability and popularity of buses, it's not likely. IMO it's big employers that should push towards setting up large bus / train hubs in cities surrounding them, allowing commuters to only need to get to the bus station themselves. There's some companies that generate multiple percents of commuter traffic pretty much everywhere. They're the ones that should also do their part, by of…

>It already is, but based on the availability and popularity of buses, it's not likely.

I guess it depends where. Here in London buses are everywhere.

It's an interesting take on who's responsibility it is to provide transport. My personal view (neither more not less valid than yours) is that it should be the job of the local authorities to provide transport (council or state). It will help companies of all sizes to grow rather than leaving the responsibility on a few big corporations, and it would give access to transport to every employee, not just googlers. That's only possible if the tax system is well thought and functioning, including taxing said big corporations.

Re: Why driverless cars may mean jams tomorrow

#73

Post by alanfranzoni »

LeonidasXIV wrote: post #52
nkoren wrote: post #30

Earlier quoted context omitted.

No, not like that. Trains work well for arterial routes that need to carry large volumes of people along predictable corridors at predictable times of day -- eg., for commuting. And yes America certainly needs to get better at investing in them. But trains don't work at all well for serving smaller volumes of people moving in stochastic patterns at arbitrary times of day. Neither do buses. Cars serve this need very w…

> People own cars to serve this need, because nothing else will (unless you're in a mega-city that can afford to run high-frequency mass transport 24/7). Uhm, I guess then 600.000 inhabitant Copenhagen must be this mega-city where high-frequency mass transport runs 24/7 (a driverless metro) and people use bikes to get around in stochastic patterns at arbitrary times of day (because there are bike lanes everywhere).

Copenhagen is exceptionally well designed IMHO, from both the biking side and the public transport side. Not all the cities are that way, and some just don't have enough room for such amenities - consider many cities in Italy with much narrower roads and many slopes, as an example.

Re: Why driverless cars may mean jams tomorrow

#74

Post by alanfranzoni »

chopin wrote: post #48
alanfranzoni wrote: post #20

Earlier quoted context omitted.

Do people really dislike ride sharing more than public transport? Why? I dislike public transport when it's ineffective. It takes me about 45 minutes to get to work by walking + train, and there's about one train every hour (less often in the morning), so it's inflexible. If I go by bike, it's about 55 minutes (but then I need a shower, which can take a bit more if your company doesn't provide the right facilities).…

If you rideshare it's likely to take longer than 25 minutes to get to work unless all sharing people happen to work and live at the same point.

If there're 4-5 of us ridesharing, the system should pool people going to similar destinations. I expect the commute to be something like 35 minutes, with the added flexibility I could bear the increased time.

Re: Why driverless cars may mean jams tomorrow

#75

Post by alanfranzoni »

ams6110 wrote: post #46
alanfranzoni wrote: post #24

Earlier quoted context omitted.

I'm not american, and I use public transport in Italy. But the public transport is simply ineffective a) from a door-to-door timing perspective and b) from a flexibility perspective. Sure, I don't live in a big city, so maybe the public transport is not as effective as it could be; but many people I spoke with even in London (and other places like Berlin, Paris, Milan) seem to share the same suffering: constantly usi…

Where I live, the buses cause significant traffic problems. They stop in driving lanes to pick up and disgorge passengers. Their stops are out of sync with traffic signals. They are slow. Self-driving cars available on demand might solve a lot of that. However, like most "utopias," I don't think we will ever achive the ideal efficiencies that self-driving car advocates imagine. The real world is too complicated.

> Where I live, the buses cause significant traffic problems. > They stop in driving lanes to pick up and disgorge > passengers.

Is that really a BUS problem in your area? This happens in Italy as well. But the root cause is cars - cars that happen to be "momentarily parked" in bus stop areas, that force bus drivers to stop in the middle of the road.

> They are slow.

Very often, that's true, they're painfully slow.

Re: Why driverless cars may mean jams tomorrow

#76

Post by catbird »

moneytide1 wrote: post #58

Driverless is great for quicker reaction times, but they cannot anticipate larger-scale situations. Perhaps if all cars were autonomous and connected it could work, but that will not happen for a very long time. When I see a heavy truck merge a mile ahead on the interstate, I will go ahead and get in the left lane. Heavy trucks cannot accelerate like a passenger car. If I can detect the age of the driver in front of…

I don't see any reason why an autonomous car couldn't be trained to move to the left lane before an on ramp, or classify neighboring cars by their observed behaviors (slow reaction time, etc).

Also, I would argue that maintaining a buffer zone in heavy traffic, though it may feel like you are breaking less/going faster, is not actually helpful. The flow rate of a section of highway (cars/hour) is the product of speed (miles per hour) and density (cars/mile). Leaving a space in front of you lowers the density, decreasing overall throughput. Ideally with self driving cars we could have them going at high speeds very close together (or even mechanically coupled like a train).

Re: Why driverless cars may mean jams tomorrow

#77

Post by moneytide1 »

catbird wrote: post #76
moneytide1 wrote: post #58

Driverless is great for quicker reaction times, but they cannot anticipate larger-scale situations. Perhaps if all cars were autonomous and connected it could work, but that will not happen for a very long time. When I see a heavy truck merge a mile ahead on the interstate, I will go ahead and get in the left lane. Heavy trucks cannot accelerate like a passenger car. If I can detect the age of the driver in front of…

I don't see any reason why an autonomous car couldn't be trained to move to the left lane before an on ramp, or classify neighboring cars by their observed behaviors (slow reaction time, etc). Also, I would argue that maintaining a buffer zone in heavy traffic, though it may feel like you are breaking less/going faster, is not actually helpful. The flow rate of a section of highway (cars/hour) is the product of speed…

Yes, the train example would be the optimal way to use autonomy. The idea of the buffer is rooted more in energy efficiency, rather than increasing flow rate. But I understand that time may be more valuable than energy in this situation, since we are talking about the throughput of economic components (worker and resource transport).

The idea is that if the buffer were used more frequently, then the average speed could increase. Multiplied by a lower density number, it could potentially be a higher flow rate. It requires more energy and time to move from a complete stop than it does to increase speed while already moving. The buffer could eliminate jams completely, if we define "jam" as standstill traffic.

Merging would be smoother because there wouldn't be stop and go. Think of all the thousands of people in a 5 mile jam stretch that slow to a halt and wave their hand while the other person takes time to look at them and make sure they really do have clearance. Every time that happens, dozens of cars behind must also come to a complete halt. With the buffer, speeds may temporarily slow but never halt when introducing new vehicles into the line. If the buffer was a standard implemented in drivers ed, then all drivers would have a protocol for jams.

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