Uber and Lyft have made San Francisco's traffic much worse, study says
Ride-hailing services like Uber and Lyft are so popular in San Francisco that they have become the single biggest factor behind the city's increasingly snarled traffic, according to a new report.
Researchers analyzed millions of trips and concluded that the services accounted for more than half of the 62% increase in weekday traffic delays between 2010 and 2016. They also found that many of the cars offering rides via Uber and Lyft did not reduce or replace private vehicles, as originally envisioned. Instead, they often increased the total number of cars on the road.
So much for the claim that ride-hailing would improve traffic - at least in San Francisco.
“It does not live up that promise,” said Greg Erhardt, a civil engineer at the University of Kentucky and lead author of the report published Wednesday in Science Advances.
Uber and Lyft both disputed the findings, saying the analysis did not account for all the factors that may have affected traffic.
Assessing the effects of ride-hailing services on traffic has proved to be a tricky task. Some previous studies have found that they reduce congestion, while others come to the opposite conclusion.
In San Francisco, it's clear traffic has gotten much worse over the last five or six years, as ride-hailing services have caught on.
“We saw a very precipitous rise in congestion,” said Joe Castiglione, the deputy director for technology, data and analysis at the San Francisco County Transportation Authority.
However, the city underwent a transformation over that same period, as tech companies and their employees flocked to the area. “How do we parse all that out?” said Castiglione, a coauthor of the new report.
The first thing the study authors had to do was figure out where and when Uber and Lyft were operating in San Francisco.
Companies have been reluctant to share such data with city officials, Castiglione said. So has the California Public Utilities Commission, which regulates the industry.
So analysts at SFCTA got creative. They partnered with researchers at Northeastern University who figured out a way to “scrape” data from Uber's and Lyft's application programming interfaces, or APIs. These APIs, which are publicly accessible, allow you to see all the cars in your area when you open up a ride-hailing app on your phone, said Drew Cooper, a modeler at SFCTA.
The Northeastern researchers created a program to mimic the Uber and Lyft apps, so they could collect data on the locations of available drivers and keep track of when they had picked up or dropped off a passenger. Team members downloaded the data every 5 seconds during a 6-week period in the fall of 2016, and Cooper crunched the numbers.
He calculated that Uber and Lyft accounted for about 170,000 trips in San Francisco on an average weekday - representing up to 25% of all trips at peak hours in some neighborhoods.
“The trips are primarily happening in the most congested parts of the city at the most congested times of day,” Castiglione said.
Those results were released in 2017. But they didn't tell researchers how much ride-hailing activity actually affected traffic. So they turned to a model that simulates how people get around San Francisco. This allowed them to calculate what traffic would have been like in 2016 considering recent changes in population and employment but without Uber and Lyft.
Erhardt and his colleagues also looked at data from a traffic-tracking company to get a picture of how real-world conditions changed over time.
By comparing traffic patterns in 2010 - when ride-hailing services were effectively absent - with those from the real and simulated versions of 2016, the researchers were able to tease out how much of the increased congestion was caused by the companies.
Their results suggest that the number of miles traveled on city streets and the hours spent doing so rose twice as much with ride-hailing as they would have without it. The 62% increase in the hours that vehicles spent stuck in traffic between 2010 and 2016 would have been just 22% if the city didn't have Uber and Lyft, according to the study.
The researchers found that travel times became more unpredictable too. And average speeds dropped by 13%, versus 4% without ride-hailing.
Each customer pickup and drop-off caused a significant disruption; on major roads, it was equivalent to closing the lane for more than 2 minutes, Erhardt said. Diverting stops to side roads could minimize delays, he noted.
Adding to the problem is the practice known as “deadheading,” which is when drivers travel without a passenger. This accounted for 20% of ride-hailing traffic in San Francisco. (In New York, deadheading makes up about 50%.)
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