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ASU team first to prove Uber eases traffic congestion

ASU researchers find that Uber ride-sharing reduces traffic congestion for all.
September 29, 2016

Researchers find that ride-sharing service saves travel time, gas

Editor's note: This story is being highlighted in ASU Now's year in review. To read more top stories from 2016, click here.

A trio of Arizona State University researchers has quantified the “Uber effect” by completing the first study to prove that when the ride-hailing service enters an urban market, it reduces traffic congestion, cuts travel time and saves gas for all drivers. 

The new study, analyzing the largest of several services that allow people to book rides through a smartphone app, puts the value of that savings at more than $1 billion nationwide since 2011, including 66 million hours and 30 million gallons of fuel.

For example, in metro Phoenix, researcher Ziru Li said that translates into about 1.8 million hours that are not spent in traffic jams and more than 900,000 gallons of fuel saved. Together, the time and gas saved are valued at about $43 million since Uber entered the market in 2012.

The study was done by three information systems researchers in ASU’s W. P. Carey School of Business: Yili Hong, an assistant professor; Zhongju Zhang, an associate professor; and Li, who is a doctoral student and research associate. Their work will be presented at several conferences this fall, including the Hawaii International Conference on System Sciences, the Institute for Operations Research and the Management Sciences annual conference and the International Conference on Information Systems annual conference.

“Ride-sharing is a big topic in our discipline,” Hong said. “We study how information technology, which Uber and ride-sharing are a part of, impacts society, and we were intrigued by this big phenomenon.”

Uber and other ride-hailing services such as Lyft — which allow riders to book transportation from drivers who use their personal vehicles — have sparked intense fights over licensing and regulation. Traditional taxi and limousine services have said the ride-hailing firms are avoiding costly requirements. The ride-hailing firms, meanwhile, have said they’re open to regulation.

The services have been suspended or banned in some places, though Uber now operates in more than 400 cities around the world.     

Uber, which started in San Francisco in 2011, had no involvement in the study and was selected for research because it’s by far the largest service of its type, the researchers said.

“We were brainstorming good research topics, and we came across a lot of heated debate about the ‘Uber effect,'” particularly in New York City, Zhang said. The team wanted to see what the broader effect was.

Because they wanted to compare traffic before and after Uber, the ASU team had to find out when the service entered a market. They did that by combing through hundreds of news reports, cross-referenced with data on Google searches.

Then they took detailed traffic dataTraffic data came from the Urban Mobility Report from the Texas A&M Transportation Institute and the Federal Highway Administration. and came up with more than 900 observations of 87 urban areas over 11 years that led to their conclusions.

“Basically, in research, we look for statistical significance, and even with the most conservative estimates, we are able to find significant effectsThe team also found that the more types of Uber services that are available in an urban area, the more traffic congestion is lessened.,” Hong said.

The team also controlled for coincidence — that traffic congestion decreased after Uber arrived but not because of it.

“We are using econometric models to establish this causality,” Hong said. “This ride-sharing service really is causing reductions in traffic reductions. It’s not just an association.”

Hong said that the team’s study doesn’t provide direct evidence that more ride-hailing services would cut traffic even further, but their analysis of Google searches might imply that. 



This type of study requires big data sets, and the team hopes to work with companies to get access that information.

In the paper, the team discussed reasons why the sharing economy might lessen traffic:

  • Uber increases vehicle occupancy. A 2014 study found that ride-sharing cars averaged 1.8 passengers compared with 1.1 in a taxi.
  • The ride-hailing app model means that drivers don’t have to cruise the streets looking for passengers.
  • People are depending on sharing rather than owning cars. One survey of more than 6,200 households found that sharing replaced nine to 13 owned vehicles.
  • Uber increases trip bundling, with passengers doing several things in one trip rather than making several different trips.
  • Surge pricing encourages people to use ride sharing at off-peak times so they pay less.

The three researchers said it was important for them to be familiar with ride hailing.

“One of the things we’ve learned throughout the years is that if you want to research something, you better be a user yourself so you can understand it,” Zhang said.

He hopes the study results can inform the debate over ride hailing.

“The argument many cities use to not let Uber enter into the local market is that it can bring negative social issues, such as traffic congestion. We would hope our findings could convince them.”


Top photo: ASU researchers in the W. P. Carey School of Business found that the Uber ride-sharing service reduces traffic in urban areas. They are (from left) Yili Hong, an assistant professor; Zhongju Zhang, an associate professor; and Ziru Li, who is a doctoral student and research associate. Photo by Charlie Leight/ASU Now

For media inquiries, contact Leslie Minton at

Mary Beth Faller

reporter , ASU Now


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‘Faithful Forest’: ASU poet pens ode to national park

ASU professor and poet laureate pens #NPS100 poem on Petrified Forest.
September 29, 2016

Work by Alberto Ríos, Arizona’s official poet laureate, is part of initiative marking park agency's centennial

The striking landscapes that make up our national parks can inspire profound exclamations in even the most ineloquent of visitors. But for an occasion such as the National Park Service's centennial, a creative initiative is bringing out the pros: poets lending their words to the nation. 

On Thursday, the first fiveFirst to be featured are writers from Arizona, Iowa, Louisiana, North Carolina and Pennsylvania. of 50 commissioned poems — one for each state — were released by the Academy of American Poets for the “Imagine Our Parks with Poems” initiative. Arizona's entry was written by Alberto Ríos, an Arizona State University Regents’ Professor and the state’s official poet laureate

Ríos was asked to write a contribution on an Arizona national park of his choice. His poem, “Faithful Forest,” lauds the state’s quieter natural wonder — Petrified Forest National Park (pictured above).

Alberto Rios
Alberto Ríos

“The Grand Canyon, of course, speaks for itself,” said Ríos. “The Petrified Forest is a place with a wonderful name but something of a baffling first impression. This was something I could do: help us to understand where we are and how important the greater conversation of the world around us truly is.”

Petrified Forest National Park is in northeastern Arizona, about 50 miles from the New Mexico boundary on Interstate 40. It is known for the large number of fossilized trees and other Late Triassic flora and fauna, as well as for its colorful landscapes.

Engaging people with such memorable places is the goal of the larger “Imagine Your Parks” grant initiative from the National Endowment for the Arts, created in partnership with the National Park Service, an initiative of which the Academy of American Poets project is a part.

Ríos was the natural choice for an Arizona poet. He has described much of his work as written “for public purpose,” since he is often called on to create poems commemorating occasions and events. He has written poems for the visit of Mexico’s President Vicente Fox to Arizona in 2003, for the inaugurations of Arizona Gov. Janet Napolitano in 2003 and 2007, for a permanent installation on the U.S.-Mexico border at Nogales, and, most recently, upon the death of former Arizona Gov. Raul Castro in 2015.

“I have come to see the value of paying attention,” Ríos said, “and the wisdom of paying attention not simply to oneself. Paying attention to and for others, and to the things of this world as well — this has given me a new work, a next level of public as well as personal consideration.”

The U.S. National Park Service turned 100 on Aug. 25. According to the park service website, “The centennial kicks off a second century of stewardship of America's national parks and engaging communities through recreation, conservation, and historic preservation programs.”

Ríos’ poetic statement follows his poem below. 


Faithful Forest
Alberto Ríos


I will wait, said wood, and it did.
Ten years, a hundred, a thousand, a million —

It did not matter. Time was not its measure,
Not its keeper, nor its master.

Wood was trees in those first days.
And when wood sang, it was leaves,

Which took flight and became birds.



It is still forest here, the forest of used-to-be.
Its trees are the trees of memory.

Their branches — so many tongues, so many hands —
They still speak a story to those who will listen.

By only looking without listening, you will not hear the trees.
You will see only hard stone and flattened landscape,

But if you’re quiet, you will hear it.



The leaves liked the wind, and went with it.
The trees grew more leaves, but wind took them all.

And then the bare trees were branches, which in their frenzy
Made people think of so many ideas —

Branches were lines on the paper of sky,
Drawing shapes on the shifting clouds

Until everyone agreed that they saw horses.



Wood was also the keeper of fires.
So many people lived from what wood gave them.

The cousins of wood went so many places
Until almost nobody was left — that is the way

Of so many families. But wood was steadfast
Even though it was hard from loneliness. Still,

I will wait, said wood, and it did.


About this poem

I remember first coming to the Petrified Forest as a very young man and wondering what all the fuss was about. There didn’t seem to be much there. Petrified wood lay everywhere, in greater and lesser amounts, but it just seemed like curious rock. In driving through the area, which is large, however, the more the place began to change before me. It was a drive through time.

The great expanses of northern Arizona are geologic in their scope — human measures are not adequate to understanding them. The Grand Canyon we can “see” — but to see the Petrified Forest, you must use a different set of eyes.

Arizona is a place in which the human imagination is called upon to be complicit in understanding that this desert once was — so magically in this arid place, this very specific place — a forest. 

The openness of this region lends itself to myth, to big story, to the engaged imagination hard at work for centuries in the act of understanding and in trying to see what is profoundly in front of us. In this effort, the desert is full of mirages, which may not be mirages at all but living acts of memory held in common with the Earth.

—Alberto Ríos


Ríos was named inaugural poet laureate for the state of Arizona in 2013, and a chancellor of the Academy of American Poets in 2014. He is the author of 10 books and chapbooks of poetry, three collections of short stories, and a memoir. His books of poems include, most recently, “The Dangerous Shirt,” preceded by “The Theater of Night,” winner of the 2007 PEN/Beyond Margins Award. His memoir about growing up on the Mexico-Arizona border — “Capirotada” — won the Latino Literary Hall of Fame Award and was designated as the One Book Arizona choice for 2009. His work is regularly taught and translated, and has been adapted to dance and both classical and popular music. He has taught at ASU for more than 30 years and also holds the Katharine C. Turner Endowed Chair in English.

Kristen LaRue

communications specialist , Department of English