
Why predicted gridlock almost never happens - samsolomon
http://cityobservatory.org/carmaggedon-stalks-atlanta/
======
awjr
A number of cities around the world have removed highways through the centre
of their cities without impacting congestion noticably.

Breass Paradox
[https://en.wikipedia.org/wiki/Braess%27_paradox](https://en.wikipedia.org/wiki/Braess%27_paradox)

Removing shortcuts within a system can make the system more efficient.

Induced Demand/Traffic Evaporation
[https://en.wikipedia.org/wiki/Induced_demand](https://en.wikipedia.org/wiki/Induced_demand)

Build it and make it easier to use will generate more traffic. Remove it and
the traffic just vanishes. Traffic Evaporation surprises many planners. The
problem being that they assume traffic is just like water and must go
somewhere else. Traffic is intelligent movement of individuals and people
shift modes when one mode becomes less efficient either in time and/or money.

~~~
Declanomous
I wonder how WAZE interacts with the Breass Paradox. When I started using it,
I noticed it could cut 10 minutes off my commute. Over time I noticed that
more and more people were taking shortcuts, and now my commute is longer than
it would have been had I just stayed on the standard route 5 years ago.

Part of that is surely the growing population with cars in the neighborhoods
in-between where I live and where I work, but I wouldn't be surprised if WAZE
somehow made traffic worse.

~~~
awjr
WAZE is interesting as is Google Directions. In effect they have enabled side
roads to 'absorb' the increase in car use without having to deal with actual
shifting people out of cars into other modes.

In the WAZE Driver Satisfaction survey, the Netherlands came out on top. I'm
guessing this is because so many people can choose not to drive to
work/school/shops/etc.
[https://www.waze.com/driverindex](https://www.waze.com/driverindex)

The Netherlands also have the happiest children in the world with the best
child travel independence. I'm guessing creating a world where active travel
(walking and cycling) is built into your environment from the getgo sets you
up for life to be active. Their diet is bloody awful. ;)

------
spcelzrd
Atlanta commuter here. The bridge collapse has impacted my daily drive. The
first half of the trip is much quicker. The second half is much slower.
Results in a slightly longer daily commute.

There are certain areas of the city I just won't go to until they fix the
bridge. Last night I had to go to Ansley Park and the traffic at Piedmont and
Monroe was absurd. Not an area I visit frequently, but there was gridlock, and
I suspect most people were there because they had no other route.

285, the perimeter road, is much worse in both directions at all times of day.

I've lived in Atlanta most of my life. I would prefer we spend no more money
on roads and instead funnel those resources into public transit.

~~~
oddlyaromatic
Also live in Atlanta, commute is the same story, I was laughing all the way
down 85 till the 3/4 mile backup at my exit, and I ended up just a little
late.

~~~
madcaptenor
I had the easiest commute I've had in a while yesterday, complete with the
miracle of traffic moving just fine on 285. It reminded me of one of those
days where there are flurries is some mountain town and so everybody in
Atlanta stays home.

On the other hand, Friday evening was one of the worst Atlanta traffic jams
I've ever been in, so I don't know what the new normal is.

------
maxsilver
> "people travel on roadways because the capacity is available for their
> trips, when when the capacity goes away, so does much of the trip making."

> "46,000 fewer trips per day across the river after the bridge collapsed."

Can we also start including quality of life and transportation times and
housing costs in these measurements. 46,000 people wanted to go somewhere and
couldn't. The article plays this like a success, but that sounds like a
quality-of-life drop for many people.

Something can still be a bad idea, even if it is not "the end of the world".
Tearing down useful infrastructure is still a bad idea, even if it doesn't
literally destroy the city.

~~~
Symbiote
OK, but you also need to consider the quality of life for people living or
working near the roads -- that increases when there is less traffic.

~~~
scythe
When I lived in Atlanta I had an apartment in south Buckhead within sight of
I-85 actually quite close to where it collapsed. I don't recall many sleep
disturbances. But when I lived in a complex on 10th street there were sirens
going down the road at all hours of the night.

The low grumble of car motors is pretty minor by noise standards. Fire engines
and ambulances however...

~~~
closeparen
Try rail level crossings with train horns every few minutes.

It's amazing to me that car tires are even considered noise. That's just the
floor. There are much worse offenders in urban environments.

I guess in a rural or suburban environment you might have actual silence
without the highway, but I've never noticed the highway to be much louder than
the wind unless a particularly bad diesel engine, illegal-exhaust motorcycle,
or emergency vehicle is passing.

~~~
Symbiote
Where I live, in the centre of Copenhagen, is so quiet that people from other
cities remark on it when they visit.

Cars drive at 30km/h (at most), and very few have reason to drive past. There
aren't any 'fast' roads nearby, the nearest that could qualify is about 1km
away.

Most noise is from people talking as they walk past.

------
sandworm101
So blocking up a road results in fewer trip in the affected area? This is
news? Block up two roads and you will see even more reduction. Heck, block all
the roads. Traffic solved.

Local congestion is only half the story. How many people simply altered
routes, perhaps traveling longer? How many instead went elsewhere rather than
not go anywhere? I want to see not a city-wide but an area-wide measurement of
total miles travelled. That number matters more (economically,
environmentally) than local congestion. If cutting traffic in the city core
results only in greater traffic elsewhere, that is no net good. In fact it
only contributes to urban sprawl as people travel further to reach various
destinations.

~~~
eli
Just like adding a lane doesn't improve traffic much because more people use
the road

~~~
nitrogen
That claim is frequently used on HN to justify anti-driving policies, but the
economic cost/benefit inside and outside the affected area is never
considered. If you only focus on one metric (traffic density), you miss the
bigger picture.

~~~
awjr
Well London removed two lanes of traffic and installed a 4m wide 20km
protected cycle super highway. This has increased capacity of the road by
5-10%. It's reduced the motorised vehicle traffic flow, but overall has
increased the number of people they are moving through the same space.

If the only type of transport you support on a road is the car, then you are
in a world of hurt.

In the UK, the bigger picture is that abotu 70% of road journeys are under
8km. Given good safe cycle infrastructure and maybe an eBike, most people
could switch out of cars.

~~~
sandworm101
The average age in my city is over 60. "Most people" arent going to be
rollerblading to the clinic for thier blood tests. Not everyone is a fit and
healthy millenial, nor will taking away thier cars and busses make them so.

~~~
upofadown
Over 60 people tend to not mind if their drive takes a bit longer. Over 60
people who are too old to drive tend to take the bus.

~~~
scythe
You and I have met very different "over 60 people".

------
lisper
This is a very misleading article in many ways, but I'll just point out one:
they show a Google Traffic map showing traffic normal "late in the morning."
But to measure how much time people are spending in traffic you can't just
take one snapshot. Traffic might be the same at 11 AM while rush hour
congestion now extends for several extra hours before and after what it did
before. Based on anecdotal evidence in other comments here I would bet that is
what is actually happening.

------
crusso
I live in an Atlanta suburb. My commute back from the airport (definitely a
route impacted by this road collapse) this past Friday morning was almost
twice as long as it normally is at that time of day.

Before the news of the collapse, I was planning on performing an errand in
midtown on my way home - but going right through town would have been
especially painful since the normal route home from there is over the
collapsed roadway.

People I've talked to in my neighborhood are avoiding going into or through
Atlanta if at all possible. They're finding ways to make even otherwise
mandatory trips "discretionary".

This article is a bit like the Y2K aftermath where many claimed that the hype
was overblown. While it's true that the direst of predictions didn't come to
pass, harping on those predictions as though they didn't effect behavioral
changes seems to be ignoring half the picture.

~~~
spcelzrd
I live in town and feel the same way. Some trips just aren't worth it. It
would be easier for me to go to Chattanooga than Perimeter Mall. Most areas of
Midtown are really easy though, so no change there.

------
woofyman
I live in Atlanta and this article is false. First of all, it's spring break
and the schools are closed which reduces traffic. Surface streets have become
parking lots as people find alternate routes around the interstate. This has
affected lots of the local businesses. It's dangerously affected emergency
response times for firetrucks and ambulances.

~~~
squozzer
So do I, and won't argue with your take on the situation. But I also remember
1996 and how the news predicted a disaster of Olympic proportions. Turns out
my commute during the Olympics was the fastest I can remember.

~~~
woofyman
They did a good job of scaring people into taking vacations, telecommuting,
etc. But a lot of businesses were hurt, especially restaurants. It's was great
for me. You could walk in to any restaurant without a reservation.

~~~
madcaptenor
In San Francisco this is called the "Burning Man rapture".

------
atlantacrackers
Atlanta resident. Commutes are longer by a factor of 2 if not more. A co-
workers commute from Roswell to Cumberland that did take 25 minutes is over an
hour since the bridge fell. And, that commute doesn't go anywhere near the
bridge.

Additionally, many schools are on spring break this week further reducing
traffic.

While it might not be total gridlock, the traffic is being impacted
significantly and will continue to be.

------
chairmanwow
I would love to see a ridesharing company weigh in on how trip volume /
average trip length / average trip duration / average street road speed has
been affected by the collapse. They are the only party I can think of that
would have accurate data on this subject.

This article focuses on local traffic congestion, which I honestly don't think
is helpful in assessing the true effects of the bridge collapse.

While at first, it may be surprising that traffic isn't 10x worse without a
segment of a major highway, traffic is the flow of individuals who are aware
of traffic conditions, much like traffic on the internet.

My predictions for what is currently happening in Atlanta:

* Less trips are being taken (telecommuting / not going out for dinner)

* Mandatory trips average length has increased

* Mandatory trip average duration has increased

* Average speed on street-level roads has dropped

~~~
cvoss
Also we should keep in mind that it is currently spring break for Fulton,
Cobb, DeKalb, and Gwinnett counties. Many families are out of town or have
fewer activities to attend.

------
cperciva
Some travel is discretionary. High profile disruptions in road capacity tend
to result in a reduction in discretionary travel.

But this doesn't mean that _all_ travel is discretionary, or that road
capacity can be reduced by an arbitrarily large amount without causing traffic
bottlenecks.

------
jakub_g
If you have a big city with 1000s of road, people can adjust, like in the
internet.

I work in a small (geographically) technopolis which has 2 main roads out (so
more like intranet). Recently, a tiny secondary road was closed due to
repairs. It _was_ a carmageddon due to suddenly most of the people having to
go through the same shared 1km bottleneck.

~~~
LordKano
I live in Pittsburgh and a single disabled vehicle during the morning commute
changes everything.

A closure on one of the less traveled routes into the city also has an
enormous impact on the commute for everyone.

------
zitterbewegung
Although the gridlock is not occurring I think the fact that the claim that
less people would get on the freeway would have a significant economic impact
for destinations that the freeway makes more conveinent or reachable.

------
rplst8
I think this overlooks the number of people whose commutes would go from
manageable to very painful.

~~~
_jal
They aren't measuring misery, they're measuring traffic flow.

I absolutely take your point. Just saying that wasn't the focus.

------
neom
I ran the morning commute last Tuesday vs this Tuesday through the platform
our company builds, looks like the amount of congestion did not change, but
the locations did.
[https://twitter.com/staehere/status/849280329982644224](https://twitter.com/staehere/status/849280329982644224)

~~~
madcaptenor
That would explain why some of us in Atlanta are saying it's worse than usual
and some are saying it's better.

------
siliconc0w
Less cars on the road isn't necessarily a categorical good - people are likely
driving around for a reason. Closing roads will have subtle and long term
impacts we clearly don't fully understand yet.

------
athenot
The original point may still hold but an important omission in this article is
the fact that this week is spring break for most counties around Atlanta, thus
creating a much lighter load of traffic.'

Edit: I should add that current traffic feels as if it _wasn 't_ spring break.
It will be interesting to see how next week shapes to be.

------
framebit
A number of other commenters have addressed this, but for emphasis:

1\. Many commutes around the city HAVE gotten a lot worse since the bridge
fell. Anybody who has to get on 285 for anything is feeling the pain.

2\. It's Spring Break for the public schools and many private schools this
week. Let's see what happens next week.

------
treyreynolds
A few weeks ago was my first experience of living in Austin during South by
Southwest. I heard dire warnings to stay home and avoid traffic trying to
reach my 7th street office building. As you probably expect, now due to this
article, traffic was actually considerably better than my commute today!

------
awinter-py
car flow improved when 42 traffic lights zonked out in beverly (east
yorkshire, UK, the earth)

[http://www.dailymail.co.uk/news/article-3266133/All-FORTY-
TW...](http://www.dailymail.co.uk/news/article-3266133/All-FORTY-TWO-traffic-
lights-break-Britain-s-chaotic-junction-guess-happens-flow-cars-IMPROVES.html)

(kind of amusing that the number is 42)

Related conclusion is that crowdsourcing decisions works when a few conditions
are met (all related to decentralized information). More here
[https://en.wikipedia.org/wiki/The_Wisdom_of_Crowds#Four_elem...](https://en.wikipedia.org/wiki/The_Wisdom_of_Crowds#Four_elements_required_to_form_a_wise_crowd)

------
hpritch5
It's "Spring Break" for many of the counties in Metro Atlanta. This week is
one of the worst weeks to base your commute off of. Wait until next Monday and
check google maps.

------
danesparza
It just so happens the bridge collapse mentioned happened late on a Thursday,
the week before spring break. I think the real test might be on Monday 4/10 or
Tuesday 4/11 when traffic is traditionally higher.

