8,000 cars per hour per lane on the highways of tomorrow?

Started by kernals12, September 26, 2024, 04:40:36 PM

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kernals12

The rule of thumb is that a normal freeway lane can handle 2,000 vehicles per hour. The reason for that is the need for drivers to maintain a very large buffer distance from traffic in front. It's been known at least since Norman Bel Geddes published his pivotal Magic Motorways in 1939 that if cars could synchronize their speeds, capacity could be greatly increased.

Most conservative assumptions on this say that capacity could rise to 4,000 vehicles per hour assuming a uniform distance between each car. That is enough to eliminate traffic congestion in most places, especially the US, but in the world's most crowded urban areas, it will not be enough.


But we can do better still. Thisstudy says that if cars could hook up into platoons of 10 or 20 and perfectly sync all acceleration and braking movements, lane capacities of 8,000 per hour are possible. This means that a 4 lane freeway, assuming 1.25 people per car, will move about as many people as a subway line that's standing room only


thspfc

This is at least 30 years away from being a topic for legitimate discussion on a road forum.

SectorZ

We would need all vehicles to be full self driving because there is no way you could get humans to do that on their own. Every single vehicle, even one straggler in there would screw it up.

I assume given prior ideas you had, these lanes would be full-self driving only?

Max Rockatansky

Quote from: SectorZ on September 27, 2024, 07:33:45 AMWe would need all vehicles to be full self driving because there is no way you could get humans to do that on their own. Every single vehicle, even one straggler in there would screw it up.

I assume given prior ideas you had, these lanes would be full-self driving only?

Even full-self driving wouldn't be enough to get this level of synchronization K12 wants.  Each car model is going accelerate and brake differently.  Even the exact same models will be in differing states of wear and tear.  There seems to be this broad assumption with self-driving and EV proponents that stuff like brake pads don't wear down.

michravera

#4
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

kernals12

Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

It'd be a train basically

kalvado

Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

One of the things here: at small vehicle separation,  during breaking there isn't enough time to accumulate speed differential, so collision will be mostly harmless.

michravera

Quote from: kalvado on September 27, 2024, 04:58:56 PM
Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

One of the things here: at small vehicle separation,  during breaking there isn't enough time to accumulate speed differential, so collision will be mostly harmless.

... unless the lead vehicle encounters a solid immovable object ...

kalvado

Quote from: michravera on September 27, 2024, 05:02:46 PM
Quote from: kalvado on September 27, 2024, 04:58:56 PM
Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

One of the things here: at small vehicle separation,  during breaking there isn't enough time to accumulate speed differential, so collision will be mostly harmless.

... unless the lead vehicle encounters a solid immovable object ...
How would  that end differently from 2 seconds spacing?

jeffandnicole

Quote from: michravera on September 27, 2024, 05:02:46 PM
Quote from: kalvado on September 27, 2024, 04:58:56 PM
Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

One of the things here: at small vehicle separation,  during breaking there isn't enough time to accumulate speed differential, so collision will be mostly harmless.

... unless the lead vehicle encounters a solid immovable object ...

If we're still assuming all vehicles talk to each other and occupants have no control over the vehicle, the vehicles should have instant reaction time.

After all, this is how current robotic parts within the vehicles work currently under the hood.

michravera

Quote from: kalvado on September 27, 2024, 05:10:36 PM
Quote from: michravera on September 27, 2024, 05:02:46 PM
Quote from: kalvado on September 27, 2024, 04:58:56 PM
Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

One of the things here: at small vehicle separation,  during breaking there isn't enough time to accumulate speed differential, so collision will be mostly harmless.

... unless the lead vehicle encounters a solid immovable object ...
How would  that end differently from 2 seconds spacing?
With 2-second spacing you can decelerate at 1G from 19.6 m/s to 0 in 2 seconds. That's from about 45MPH to stop. Typical manual breaking isn't that good, but automatically, maybe it could be. At maximum breaking (perhaps reversing the engine?) at a couple of Gs, you could stop from higher speeds. With only 0.16 seconds of spacing, even pulling 4Gs (which will probably break your ribs), you haven't a prayer.

Also, why have our own vehicles, if we don't make any decisions and can't create spacing to maneuver to take offramps? Where's are the keys to the PA-28 or even the C-172?

kalvado

Quote from: michravera on September 28, 2024, 12:58:08 AM
Quote from: kalvado on September 27, 2024, 05:10:36 PM
Quote from: michravera on September 27, 2024, 05:02:46 PM
Quote from: kalvado on September 27, 2024, 04:58:56 PM
Quote from: michravera on September 27, 2024, 01:35:24 PM
Quote from: thspfc on September 26, 2024, 05:21:43 PMThis is at least 30 years away from being a topic for legitimate discussion on a road forum.

Basic math says that, with 2 seconds of following time, you can only do 1800 vehicles per hour (that's neglecting the length of a vehicle). Cut the time to 1 second and you double the throughput to 3600. Yeah, cut the following time to 0.45 seconds and you'd get 8000, but at 20 m/s (72 km/h), that's only 9 m between the fronts of vehicles. Chevy Suburbans are just 5.73 m. That not only gives only 0.16 s of reaction time, but requires that lead vehicles not break much faster than the trailing vehicle. There's only roughly the width of a lane between bumpers.

One of the things here: at small vehicle separation,  during breaking there isn't enough time to accumulate speed differential, so collision will be mostly harmless.

... unless the lead vehicle encounters a solid immovable object ...
How would  that end differently from 2 seconds spacing?
With 2-second spacing you can decelerate at 1G from 19.6 m/s to 0 in 2 seconds. That's from about 45MPH to stop. Typical manual breaking isn't that good, but automatically, maybe it could be. At maximum breaking (perhaps reversing the engine?) at a couple of Gs, you could stop from higher speeds. With only 0.16 seconds of spacing, even pulling 4Gs (which will probably break your ribs), you haven't a prayer.

Also, why have our own vehicles, if we don't make any decisions and can't create spacing to maneuver to take offramps? Where's are the keys to the PA-28 or even the C-172?

Couple g? 0.6 as best case scenario, 0.2-0.3 if the weather is less than perfect.

kernals12

This study says that with radar based communication, they can get latency down to just 1 millisecond.

jeffandnicole

Quote from: kernals12 on December 20, 2024, 05:52:09 PMThis study says that with radar based communication, they can get latency down to just 1 millisecond.

Is this the same radar that people say is so imperfect they need a 7 mph leeway before tickets are issued?

kalvado


kalvado

Quote from: jeffandnicole on December 20, 2024, 06:26:21 PM
Quote from: kernals12 on December 20, 2024, 05:52:09 PMThis study says that with radar based communication, they can get latency down to just 1 millisecond.

Is this the same radar that people say is so imperfect they need a 7 mph leeway before tickets are issued?
The buffer is primarily for car speedometer and US cultural speeding.
Radar is way below 1mph

Max Rockatansky

Who is the "they" that keeps getting referenced on the forum today?  There even is an active thread that even has "they" in the title:

https://www.aaroads.com/forum/index.php?topic=35523.msg2958860;topicseen#msg2958860

hotdogPi

Quote from: Max Rockatansky on December 20, 2024, 07:09:51 PMWho is the "they" that keeps getting referenced on the forum today?  There even is an active thread that even has "they" in the title:

https://www.aaroads.com/forum/index.php?topic=35523.msg2958860;topicseen#msg2958860

The person who liked your post, apparently.
Clinched

Traveled, plus
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Lowest untraveled: 36

Molandfreak

Quote from: Max Rockatansky on December 05, 2023, 08:24:57 PMAASHTO attributes 28.5% of highway inventory shrink to bad road fan social media posts.

Roadgeekteen

My username has been outdated since August 2023 but I'm too lazy to change it

Max Rockatansky

Jokes on you guys, this thread is from September.  I guess we weren't talking about AI cars enough.

Rothman

Please note: All comments here represent my own personal opinion and do not reflect the official position(s) of NYSDOT.

Quillz

I'll believe it when it happens. Reality tends to be very underwhelming and boring. 

Max Rockatansky


Roadgeekteen

Instead, we should spend money on high-speed rail around the country. I will not elaborate.
My username has been outdated since August 2023 but I'm too lazy to change it



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