Autonomous cars and car sharing will decrease traffic congestion?

Autonomous cars and car sharing will decrease traffic congestion?

Not strictly a Model 3 issue but I've seen this idea suggested in the media and I'm wondering if anyone knows why. It is simply wrong!

Here is what I see:

First of all lets look at the numbers. There are apparently about 256 million passenger cars in the US driving on average 13,500 miles. If these numbers are correct the total miles driven by the 'fleet' is 3.456 trillion miles/year. This number is what the roads handle now. If you increase total miles driven congestion goes up ... decrease this number and congestion goes down.

So lets look at where we are going ...

Privately owned (one owner) cars
- We will travel/commute the same amount(same miles driven).
- Our autonomous cars will now however drive a certain amount without anyone in them since we will be able to send them home to park or send them somewhere further away to park at a cheaper parking lot ... or to charge ... whatever (this is new miles driven).

Effect - Increase in total miles driven

Shared cars - (multiple owners)
- Owners will drive about the same as what they always did (same miles driven)
- These cars will now however need to drive themselves between owners (this is new miles driven)

Effect - fewer cars made .. but there will be an increase in total miles driven

- Driver-less taxis will be the norm and the cost to get a cab will be much lower since there will be no labour to pay for.
- More people will use taxis (fewer cars made)
- Taxis need to come get you as well as drive you to your destination (this is new and more miles driven ... total taxis go up remember).

Effect - fewer cars made .. but there will be an increase in total miles driven


Congestion will increase with autonomous cars and car sharing since in spite of fewer cars being made because total miles driven by the fleet will go up.

Make sense?

Captain_Zap | 2016年6月24日

Add to the equation population growth and it looks even less promising.

Red Sage ca us | 2016年6月24日

There is a prevailing sentiment that the United States of America is somehow dangerously underpopulated.

bb0tin | 2016年6月24日

Another issue is that electric autonomous cars can make car transport cheaper and more convenient than public transport. How many people will therefore switch from mass transit to cars? Electric autonomous cars can potentially increase the number of cars wanting to travel at peak times roughly 2X to 5X worse. We will be forced to move to ride sharing and more desirable mass transit. Elon has mentioned that he has an idea for a door-to-door mass transit system. I believe such a system will be required in the decades to come.

carlk | 2016年6月24日

In the equation there should be number of cars a highway/road can carry per hour. Autonomous driving would allow cars to go faster and packed closer but still be safe. You will also eliminate delays caused by bad driving habits and accidents. Thus efficiency of road use can be greatly improved. To go one step futher we can have dedicated smart lane with imbeded electronic signal emiter to guide cars to go even faster, packed even closer and be even safer.

Drdpharris | 2016年6月24日

All autonomous cars would not need traffic lights, stop signs etc. Much more efficient. If cars are shared, then trips can be reduced: the car that drops you at work can carry someone else home ....

bb0tin | 2016年6月24日

What you suggest is true when all vehicles are autonomous, but that is likely a decade or two away. In the meantime autonomous cars will be sharing the road with human driven cars, and so the current overall nature of traffic behavior will continue. It takes only a few percent of vehicles to disrupt smooth traffic flow.

JeffreyR | 2016年6月25日

@carlk +1 nailed it!
Also think of how many times you've been in traffic caused by an accident already out of the lanes but lookie loos insist on slowing down to gawk.

@bb0tin true, but question was 'if' not 'when' nor 'now' so it's more a matter of degrees of improvement over time. Also, if ride sharing is cheaper than mass transit, that's okay. Cities can replace buses w/ ride share units. I think taking a ride share to and from the train would make it easier and more efficient all around. Interrelated and/or nested options that feed into each other work best. We should still make biking easier and safer too for example.

topher | 2016年6月25日

You are assuming that we keep the incredibly stupid idea of one car, one passenger. Why would we do that? \

Thank you kindly.

Tstolz | 2016年6月25日

I can see future EVs being able to drive faster than humans but early versions will most certainly be slower with conservative programming. Fewer accidents is a great point!

topher - I agree ride sharing is a great idea but probably is unrelated to car sharing/autonomous driving. There is a law in psychology that says the best predictor of future behaviour is past behaviour ... so I don't see this behaviour changing personally. btw .. I haven't seen the use of 'thank you kindly' used before ... is it a cultural thing? Just curious.

bb0tin | 2016年6月25日

You said "but question was 'if' not 'when' nor 'now' so it's more a matter of degrees of improvement over time."
That is how I did approach my argument.
For the first many years of autonomous cars, the traffic will behave exactly as it does now. The number of cars on the road will actually increase because private cars, rather than parking at the end point as they mostly do now, will head on back out for the cheapest parking. This will happen in reverse at the end of the work day etc.
In the medium term, 10-20 years at least, the situation will still be the same regarding traffic flow because there will still be a lot of human driven cars. But there will now be a move away from existing mass transit. This will either go to more single occupancy private cars, or ride sharing, or better public transport. The question is why would someone, who has an autonomous electric car, choose to ride share when they can travel more conveniently alone at close to zero marginal cost? I don't believe they will, unless they can travel faster or much cheaper using ride sharing and this will require regulation and fees.
In the medium to long term we cannot have the cheap freedom to travel autonomously in single occupancy electric cars or there will be gridlock.

bb0tin | 2016年6月25日

You said "I agree ride sharing is a great idea but probably is unrelated to car sharing/autonomous driving."
For the reasons given in my reply to JeffreyR, I believe they are inextricably linked. | 2016年6月25日

The freedom of the road in one's car is a powerful emotional draw.
During the oil embargo of 1973-74 carpooling became a necessity. Not many liked the restrictions imposed on their time. As soon as the embargo lifted, carpools disappeared.

Whatever the technological advancements in the future, there will have to be very powerful incentives to increase the number of folks per car,

Just drove into Atlanta during rush hour this past Tuesday. The drive down I75 toward the I285 junction was at a stultifying 10 mph for more than 15 miles. Yet, most of the vehicles had a single occupant despite the HOV Lane.

jordanrichard | 2016年6月25日

The only thing that will reduce congestion is ride sharing/trains/buses etc. You have to reduce the number of vehicles on the road. No Super Grey computer controlled car is going to solve congestion. The issue is simple physics. When there is an increase in the number of cars at specific times, there will be congestion. Even if all the cars had TACC, that won't solve the problem of commuters coming out of the suburbs on the secondary roads, funneling onto the highway, at the same time.

topher | 2016年6月26日

"The issue is simple physics."

Physics, in this case Bernoulli's Law, says that congestion can be lessened by increasing the speed of the particles. Congestion has nothing to do with number of particles, but rather their density, and speed.

Thank you kindly.

bb0tin | 2016年6月26日

"Congestion has nothing to do with number of particles" is patently false. | 2016年6月26日

The capacity of the roadway is a critical factor, the number of ingress and egress lanes plays a role, The design of roads that invite lane crossings to reach exits is a factor.

If an average vehicle is 16 feet long and one allows a car length space between vehicles, each vehicle takes up 32 feet of a lane. A stretch of roadway that is 1 mile long and has 4 lanes will hold no more than 4 X 5280/32 = 660 vehicles at any point in time. If the vehicles are moving at 10 mph, 6600 such vehicles can pass through in a hour. If more than 100 cars try to get onto this stretch every minute, they will start backing up. Of course this is simplistic but is a way of gaining a feeling for the problem.

bb0tin | 2016年6月26日
The simplistic way to look at it is what we all intrinsically know. If you take any existing traffic system which experiences congestion, and simply add more cars, there will be more congestion.
Traffic will not travel faster due to autonomous cars for many years because most cars will still be driven by humans who cannot cope.

jordanrichard | 2016年6月26日

topher, the cars are the "particles". I look at our highway system like a funnel with the bottom being a city or large business area and the large opening being all the feeder routes to the highway. When you have "x" amount of car, everything flows smoothly through the small end. However when the number of cars coming from the feeder routes doubles, things get bottled up because only "x" amount is going to get through the mall end of the funnel.

Even if every car starting tomorrow had TACC, the problem would still exist and actual it would spread the log jam out because of the automated spacing, but there will still be congestion.

AZ Desert Driver | 2016年6月27日

I have tried carpool - can't imagine ever wanting to have my work hours dictated by rigid schedules again. Ride share? let some one else eat, take kids/dogs/smoke in MY car. yuck. Listen to their music, or banter? Haul my stuff into and out of my car every trip. more yuck.
For the life of me, I just can't see the draw to pooled resources. Busses,taxis, trains...have very few desirable traits. Airplanes travel to places where I can't drive, so I suffer the intrusions as a cost of getting to a nicer place. This thread seems to be saying the ride share should somehow be viewed as pleasant. Somebody will have to show me the path has roses along it the I'm not seeing.

PhillyGal | 2016年6月27日

It's the complete opposite of what you're saying but the future *should* significantly decrease the number of PARKED cars. Paid parking, expensive cars sitting around for 95% of their useful lives.

The only correlation could potentially be city streets that can accommodate an additional lane of moving traffic if the parking lane disappears.

bb0tin | 2016年6月27日

@AZ Desert Driver
You said "This thread seems to be saying the ride share should somehow be viewed as pleasant."
I haven't seen any post implying that at all. What is being said is that ride sharing, or more public transport, will be an absolute necessity to avoid gridlock, whether anyone likes it or not.

bb0tin | 2016年6月27日

Less parked cars in city centres is one bright spot. More parked cars in surrounding streets is the dark spot. I expect the freed parking lanes will be used for cycle lanes and drop off/pick up zones.

Red Sage ca us | 2016年6月28日

Living in Los Angeles, it seems that the only way to truly reduce rush hour traffic would be for employers to only hire people who live within a five mile radius, meaning they must pay those employees enough to live within a five mile radius, thus, they should only have their business in decent neighborhoods where people want to live. Since companies in Santa Monica, West Los Angeles, and Culver City will hire people who live in Calabasas, Sylmar, Burbank, Alhambra, Whittier, or Cerritos, that creates traffic simply due to the distance that must be traveled. When someone who lives in Riverside, Victorville, or Lancaster takes a position in Torrance, Long Beach, or Irvine that creates traffic for daily commutes. I had hoped that the majority of positions for office work would have been converted to telecommuting by now. But certain businesses seem to be vehemently opposed to not seeing their employees' faces on a daily basis. So they don't offer a 4-10 schedule, variable start times, or work from home options.

Badbot | 2016年6月28日

Red you left out Compton, I used to work there, roof leaks turned out to be bullet holes.

we invited a mobile car wash service so we did not have to go outside,
but the second time he was robbed they took his truck and wash rig and we never saw him again.

Red Sage ca us | 2016年6月28日

The strange thing about living here is... You eventually realize that no one knows how to drive -- at all. You also learn that no one has any sense of either direction -- or distance. You find out that so many people are afraid to go to an optometrist or wear glasses -- that they don't bother reading street signs.

All that creates traffic as well. Because no one knows where they are, where they or going, or how to get there. They just follow the license plate in front of them and hope that person is going where they need to be.

Tstolz | 2016年6月28日

@RedSage - good point re autonomous cars getting lost less and picking the best routes automatically. That should favour reduced congestion a bit at any rate!

john | 2016年6月28日

The research report that convinced me that autonomous cars can be found by Googling "A Roadmap for a World Without Drivers."

It's very well done, it's a must read if you're intrigued by driverless cars. Stick with it past the first parts, and read why it is logical that driverless technology will lead to higher, not lower, car sales.

john | 2016年6月28日

The research report that convinced me that autonomous cars were inevitable can be found by Googling "A Roadmap for a World Without Drivers."

It's very well done, it's a must read if you're intrigued by driverless cars. Stick with it past the first parts, and read why it is logical that driverless technology will lead to higher, not lower, car sales.

bb0tin | 2016年6月28日

I read the relevant sections of that post and I find his arguments quite unconvincing regarding car sales.
Which parts did you find convincing, and why?

topher | 2016年6月29日


Nice bald assertion without any evidence or reasoning to support it. If it is simple physics, show the equations.

Thank you kindly.

Hi_Tech | 2016年6月29日

Analyzed like true mathematicians/statisticians!
In my opinion, traffic would truly be reduced significantly, due to the driving behavior aspect (@carlk: +1), reduced incidents, and better predictive driving (related to both prior points, I guess).

BTW, don't expect to see formulas on these reducing traffic... just, trust me!

bb0tin | 2016年6月29日

You said "Nice bald assertion without any evidence or reasoning to support it."
My only assertion was that I found his arguments unconvincing.
That statement requires no physics or equations.
If you are going to troll then try and do a better job of it.
If you would like some reasoning why, then specify an argument from the author that you find convincing, and I will do so.

Thank you kindly