
How UPS trucks saved millions of dollars by eliminating left turns - rootein
http://gadgets.ndtv.com/transportation/features/how-ups-trucks-saved-million-of-dollars-by-eliminating-left-turns-1657808
======
mstade
> In the US, and other countries where you drive on the right side of the
> road, right turns are free, but for a left turn you need to wait for a green
> light.

I don't know of any other country than the US where turning right on red is
allowed, unless there's specific signage or additional traffic lights to allow
it. Indeed, the turn-on-red rule in the US seems to work inverse to how I've
seen it elsewhere – i.e. it's always allowed unless there's specific signage
saying it isn't.

I was just in the US, and I love their turn-on-red rules, and I kept thinking
that sometimes it's got to be smarter to turn right than go straight ahead,
when there's a red light, even if it may be a longer drive. Glad to see
someone took the time to figure this out.

~~~
dorfsmay
Turning right on red is one of those idea that once you've been exposed to it
you wonder why isn't everybody adopting it...

A similar idea is the train system in Munich where they built their platforms
such that they can open doors on both sides, making one side of the train the
exit, and the other side the entrance. Ever since I saw that, every single
time I wait for people getting off a crowded train, I wonder "Why?".

~~~
jventura
> Turning right on red is one of those idea that once you've been exposed to
> it you wonder why isn't everybody adopting it...

Because someone who comes from your left may go forward, or someone who comes
from your front mau turn left?

Where I live, we do not assume that we can turn right on red lights. Where and
when that's possible, we have a blinking yellow light (basically meaning
proceed with caution)..

~~~
lorenzhs
Turning right on a red light is only permitted after establishing that it is
safe to do so. Obviously you can't just assume that it'll be fine to go. The
difference between your country and the US is the default value: do you have a
blinking light permitting it in some places, or a sign prohibiting it where it
would be unsafe?

~~~
jventura
Blinking light permiting it when it is considered safe to turn (with caution).

------
leereeves
> eliminating left turns wherever possible after it found that drivers have to
> sit idly in the trucks while waiting to take the left turn to pass through
> traffic. So, it created an algorithm that eliminated left turns from
> drivers’ routes even if meant a longer journey.

Sounds reasonable.

> In 2005 ... the total distance covered by its 96,000 trucks was reduced by
> 747,000km. In 2011, ... the company had reduced distance travelled by trucks
> by 20.4 million miles. A recent report by The Independent says that the
> total reduction in distance travelled by UPS trucks now stands at 45.8
> million miles.

But how does eliminating left turns even it means a longer journey reduce the
total distance travelled?

Edit:

The Independent article referenced here explains:

> The efficiency of planning routes with its navigation software this way has
> even helped the firm cut the number of trucks it uses by 1,100, bringing
> down the company’s total distance travelled by 28.5m miles – despite the
> longer routes.

~~~
gjem97
I think "created an algorithm" is probably overselling it a bit. Clearly they
already had a route planner, didn't they just modify it to add extra cost to a
left turn?

~~~
lorenzhs
Incorporating turn costs into route planning is actually not that easy! For
one it increases the amount of data you need (street layout, type of
intersection, etc) and a lookup to add the appropriate penalty. But more
importantly, it doesn't play well with many speed-up techniques.

Two papers on the subject, applying turn costs to the two most popular speed-
up techniques (I don't know if UPS uses either of these, though):

[https://algo2.iti.kit.edu/download/turn_ch.pdf](https://algo2.iti.kit.edu/download/turn_ch.pdf)

[http://i11www.iti.uni-
karlsruhe.de/extra/publications/dgpw-c...](http://i11www.iti.uni-
karlsruhe.de/extra/publications/dgpw-crp-11.pdf)

The first author of the first paper now works at Google, and the authors of
the second paper used to work at Microsoft Research and now are at Apple and
Amazon. Make of that what you will :)

------
Unbeliever69
It's funny because occasionally my wife will tell me to take a certain route
to a destination because that is what her traffic app told her was the fastest
route. I'll disagree on the basis of this experiment; that the "fastest route"
has too many left turns and that my route is better because it has fewer.
Needless to say, she is never amused. Maybe after this news I'll be
vindicated!

~~~
dx034
Wasn't Waze known to prefer routes that consisted of an incredible amount of
left turns and small roads? Haven't checked if they changed the algorithm.
Found that Google Maps is hard to beat on their preferred route usually.

~~~
lnanek2
At least in NJ, Google Maps typically does a terrible job. When I go from my
home to Costco, I take one small road to the highway, take the highway, get
off, and take one small road to Costco. It's very fast and easy. Makes a big L
on the map, basically.

Google Maps ignores the highway and has me make twenty alternating left and
right turns on tiny backroads. It's grueling, a lot of work, and you can't
even go fast on them. All because Google Maps is trying to cut the diagonal
from one end of the L to the other for a shorter distance. In terms of trip
duration, it fails horribly, though.

~~~
euyyn
That's odd, as Google Maps optimizes on duration, not distance: It takes speed
into account.

Maybe it's not taking into account how fast can cars make each of the turns?

------
snrplfth
This is an impressive result, but not exactly a UPS exclusive. Pretty much any
vehicle routing software worth using has offside-turn-minimization options,
usually as one of several 'weighting factors'. For example, almost every
garbage collection service of any size minimizes its offside turns.

------
amelius
Does typical navigation software assign the same cost to a left turn as a
right turn?

~~~
lorenzhs
Since you _need_ turn restrictions if you want to compute routes that users
can actually follow, adding different costs for different kinds of turns
(left, right, U-turn) is easy.

See my other comment in this thread on the challenges associated with
incorporating turn costs and restrictions in gerenal:
[https://news.ycombinator.com/item?id=13616676](https://news.ycombinator.com/item?id=13616676)

~~~
euyyn
> Incorporating turn costs into route planning is actually not that easy! [I]t
> doesn't play well with many speed-up techniques.

+

> Since you need turn restrictions if you want to compute routes that users
> can actually follow, adding different costs for different kinds of turns
> (left, right, U-turn) is easy.

Does this mean all those speed-up techniques don't produce routes that are
actually allowed? What's the point of developing them?

~~~
lorenzhs
Nah, it's just that it took work to integrate turn restrictions, and that that
results in a bit of a slowdown.

It's easier to do research on a more limited version of the problem (shortest
path in a road graph with a suitably chosen edge weight function) and then
generalise than start out with the most general formulation. The results are
wild: these techniques are millions of times faster than Dijkstra's algorithms
and provably produce the exact same result. It's what makes Google Maps
possible.

------
eggie5
i talked to my friend, a UPS driver, about this last year when this same story
surfaced on HN. He said it's not really true and that they turn left all the
time -- but he was aware of some training about it.

~~~
tiffani
Right. It's a great story, but I've seen many a UPS truck take a left turn.

------
vermontdevil
Hence the need for more roundabouts.

------
d--b
> In 2005, a year after it announced that it will minimise left turns, the
> company said that the total distance covered by its 96,000 trucks was
> reduced by 747,000km, and 190,000 litres of fuel had been saved.

Er... I understand that you may reduce your fuel consumption by not waiting at
red lights, but that the total distance driven has been reduced is clearly
wrong!

Guys, you have a bug in your spreadsheet!

~~~
deelowe
Maybe they also implemented a better navigation algorithm as part of this? The
media likes to reduce everything down to soundbites, but IIRC, this is a
rather large effort within UPS to improve routes in general. The left hand
turn optimization was just one of the outcomes of this.

------
briankwest
Yes they may save money doing this, but when you do that follow your driver
for your delivery thing they just came out with, It looks like your driver is
on crack the travel patterns make no sense. No order. They are all over the
place, similar to how Delta does connecting flights.

~~~
dx034
Worth mentioning that many drivers will be self-employed and have no such
software. UPS seems to give all drivers a software with a route to follow,
many others won't bother (as they pay the driver by delivery).

------
shakencrew
A different article about this was discussed on Hacker News before:
[https://news.ycombinator.com/item?id=7538316](https://news.ycombinator.com/item?id=7538316).
The cited article also references the Mythbusters video.

------
sctb
Discussion from a few years ago:
[https://news.ycombinator.com/item?id=7538316](https://news.ycombinator.com/item?id=7538316)

------
Theodores
This optimisation must exist at a basic level in all satnav software because
journey time must be longer for the route with more left turns, as fed back
into the system from previous journeys by other users.

It would be an interesting experiment to see how different consumer grade
satnav systems compare on this pure travelling salesman problem.

~~~
lorenzhs
It's not TSP. In TSP, you have a graph and want to visit _every node exactly
once_. Here you have a (road) graph and want to visit _some set of nodes_ (the
delivery addresses) _at least once_ (it's okay to drive past a house where you
dropped off a parcel earlier if that somehow makes the journey shorter).

Also, consumer satnav systems don't support this kind of query. You can't plug
in a list of dozens of destinations and ask for the shortest path to get you
to all of them, in any order.

~~~
DerekL
It reduces to a special case called the _metric_ TSP. If going through node C
is shorter than going from A to B directly, then just replace the A-to-B
distance with the length of A-to-C-to-B. It's just as hard to solve as regular
TSP, but easier to approximate.

~~~
lorenzhs
Well yeah it's clearly still NP-complete. But the TSP (or variant thereof)
isn't related to the routing engine at all, as the routing engine only defines
the edge weights. They're fairly orthogonal problems. Logistics software needs
to solve both, but consumer satnav doesn't.

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spraak
This is why I love data science

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imcoconut
now that's what I'm talking about. good for ups.

