It looks like all of LA is on the 405 right now.
But...how many people is this? And, better yet, how many trains would it take to move them?
Let's do the math.
๐งต
But...how many people is this? And, better yet, how many trains would it take to move them?
Let's do the math.
๐งต
https://twitter.com/KTLA/status/1463357141822029824
We're looking at the interchange of I-405 and I-10 in Los Angeles, facing south.
When we zoom out, we see a full view of I-405 from Ohio Ave to Sepulveda Blvd, a distance of 5.8 miles, or ~30,500 feet.
When we zoom out, we see a full view of I-405 from Ohio Ave to Sepulveda Blvd, a distance of 5.8 miles, or ~30,500 feet.
The 405 is five lanes in each direction for this entire stretch, plus auxiliary (merge) lanes, so essentially 12 lanes across.
Some quick multiplication gives us 305,000' of through lanes and 61,000' of auxiliary lanes.
This is about 160(!) acres of space in total.
Some quick multiplication gives us 305,000' of through lanes and 61,000' of auxiliary lanes.
This is about 160(!) acres of space in total.
Now we need to get lane density. A good approximation for heavily congested mixed traffic is 40' per vehicle.
A passenger car is ~15', but you need space between cars, and some of the traffic is made up heavy trucks.
I also verified this by counting cars in the video.
A passenger car is ~15', but you need space between cars, and some of the traffic is made up heavy trucks.
I also verified this by counting cars in the video.
Aux lanes tend not to be as congested, so we'll say that they have a vehicle every 80'.
Thru lanes:
305,000' * (1 vehicle/40') = 7,625 vehicles
Aux lanes:
61,000' * (1 vehicle/80') = 763 vehicles
Setting aside on/off ramps, that's a total of ~8,400 vehicles.
305,000' * (1 vehicle/40') = 7,625 vehicles
Aux lanes:
61,000' * (1 vehicle/80') = 763 vehicles
Setting aside on/off ramps, that's a total of ~8,400 vehicles.
The FHWA assumes an average vehicle occupancy of 1.7 people per vehicle. Let's assume since it's the holidays that that's higher, and round up to 2.
So the total number of people actually traveling on the 160 acre stretch of roadway is...
About 17,000.
So the total number of people actually traveling on the 160 acre stretch of roadway is...
About 17,000.
And while that *sounds* like a large number, in transportation terms...it's really not.
A single very crowded BART car can hold about 200 people, or 2,000 people in a 10-car train.
Meaning we're looking at about 8.5 trains worth of people.
A single very crowded BART car can hold about 200 people, or 2,000 people in a 10-car train.
Meaning we're looking at about 8.5 trains worth of people.
At peak capacity through the Transbay Tube (which connects Oakland and San Francisco), BART can move 23 trains per hour per direction, or one every 2 minutes 40 seconds.
This is a *theoretical* maximum of 46,000 per hour on a single line of track (actual ridership is lower).
This is a *theoretical* maximum of 46,000 per hour on a single line of track (actual ridership is lower).
The upshot:
Every single person on the 405 in this 6 mile length of 12-lane freeway could ride on one train line between West Oakland and San Francisco (the same distance) in about 30 minutes.
Every single person on the 405 in this 6 mile length of 12-lane freeway could ride on one train line between West Oakland and San Francisco (the same distance) in about 30 minutes.
Note that that's everyone moving in both directions of freeway (12 lanes) fitting into 1 "lane" of train line.
But not only is the width needed only 1/12th as much, the length is also wildly different.
85 BART cars lined up would be about 1.2 miles long, or 1/5th the length.
But not only is the width needed only 1/12th as much, the length is also wildly different.
85 BART cars lined up would be about 1.2 miles long, or 1/5th the length.
Just to use another example, the Shinkansen (Japanese Bullet Train) runs 16 trains per hour per direction, with a capacity of 1320 people per train.
At full capacity, this many people could pass through in 48 minutes, everyone in their own seat.
At full capacity, this many people could pass through in 48 minutes, everyone in their own seat.
All of this to say, cars (and the infrastructure to move them) take up a whole lot of space.
But *people* don't.
When we allow people to move in space-efficient ways, we will find that we don't have to devote truly massive amounts of space to our transportation system.
/๐งต
But *people* don't.
When we allow people to move in space-efficient ways, we will find that we don't have to devote truly massive amounts of space to our transportation system.
/๐งต
A couple more thoughts.
There is some confusion about one-way vs two-way travel, namely I compared 12 lanes of two-way cars vs one-way train throughout, which actually disadvantages the train.
Let's clear that up.
There is some confusion about one-way vs two-way travel, namely I compared 12 lanes of two-way cars vs one-way train throughout, which actually disadvantages the train.
Let's clear that up.
The Transbay Tube runs 23 trains per direction per hour.
Imagine that we have half of these 17k people on either side of the Bay, 8500 at West Oakland and 8500 and Embarcadero in SF.
A train comes every 2.6 minutes and each one picks up 2k people (or 1k more comfortably)
Imagine that we have half of these 17k people on either side of the Bay, 8500 at West Oakland and 8500 and Embarcadero in SF.
A train comes every 2.6 minutes and each one picks up 2k people (or 1k more comfortably)
Assuming people are packing on the trains, every one of those 17k people is *on* a train in 11 minutes and to the other side of the Bay in 18 minutes.
More comfortably loaded, it's a total of 30 minutes to get everyone to switch stations.
More comfortably loaded, it's a total of 30 minutes to get everyone to switch stations.
Also, throughout matters, but so does speed.
How *long* does it take people to get from A to B?
We don't get to see the video long enough to judge speeds, but I'd guess ~12 mph.
At that rate, it takes 30 minutes to travel 6 miles, a distance that BART traverses in 7 minutes.
How *long* does it take people to get from A to B?
We don't get to see the video long enough to judge speeds, but I'd guess ~12 mph.
At that rate, it takes 30 minutes to travel 6 miles, a distance that BART traverses in 7 minutes.
And as @SFBART points out, the Transbay Tube throughput is only going to increase.
Their ongoing Core Capacity Program will improve increase the number of trains from 23 per direction per our to 30 per direction per hour!
Their ongoing Core Capacity Program will improve increase the number of trains from 23 per direction per our to 30 per direction per hour!
https://twitter.com/SFBART/status/1463602827847036930
Some people are having a hard time with the use of thought experiments.
So, for the record, this *is not* a proposal to turn 6 miles of the 405 into a train line.
It is rather an illustration of the spatial efficiency of various travel modes.
So, for the record, this *is not* a proposal to turn 6 miles of the 405 into a train line.
It is rather an illustration of the spatial efficiency of various travel modes.
https://twitter.com/noahnonymous/status/1463605563007254530
And yes, for those wondering, this whole thread is indeed a long subtweet of Elon Musk and his breathless acolytes.
https://twitter.com/greenmetric/status/1463574472909213700
This thread would not be complete without @alon_levy's crayon map of LA rail.
Find the map here:
google.com/maps/d/u/0/vieโฆ
and the post about it here:
pedestrianobservations.com/2017/09/15/futโฆ
Find the map here:
google.com/maps/d/u/0/vieโฆ
and the post about it here:
pedestrianobservations.com/2017/09/15/futโฆ
Pleased to see that my travel time estimate was pretty good.
Displeased to see that Google Maps is recommending that people whip through local streets instead of driving on the 405.
Displeased to see that Google Maps is recommending that people whip through local streets instead of driving on the 405.
https://twitter.com/WarrenJWells/status/1463545372198854657
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