Uber and Lyft vehicles rack up over half a million miles every day on San Francisco streets, according to a report being released Tuesday by the San Francisco County Transportation Authority, which manages local congestion.

Ride-hailing cars make more than 170,000 trips within the city every weekday, while putting in some 570,000 vehicle miles, the report said. That figure is 6.5 percent of total weekday vehicle miles in the city. When only considering trips that start or end within the city — the focus of the authority’s study — ride-hail vehicles amount to a fifth of all vehicle miles.

“The perception that there are a tremendous number of (Uber and Lyft) vehicles out on the streets today is, in fact, true,” said Joe Castiglione, the authority’s deputy director for technology, data and analysis. “We see huge numbers of trips across all days of the week, primarily concentrated in the most congested parts of the city and at the most congested times of day.”

Some 5,700 Uber and Lyft cars roam the streets at the weekday peak of 6:30 to 7 p.m., the report said. The busiest time, Fridays from 7:30 to 8 p.m., sees more than 6,500 ride-hailing cars. The report did not distinguish between Uber and Lyft trips; the two companies account for virtually all ride-hailing in San Francisco.

The app-summoned vehicles are heavily concentrated in popular areas such as the downtown core, South of Market, the Mission and Van Ness corridors, Pacific Heights and the Marina. In SoMa and downtown, ride hailing accounts for a quarter of all in-city trips at peak commute periods (6 to 9 a.m. and 3:30 to 6:30 p.m.). In outer neighborhoods like the Sunset, their impact is far lower.

Still, Uber and Lyft cars “provide broader service across the city than taxis, particularly in the western neighborhoods,” the report said. But they provide fewer trips relative to the population in lower-income areas such as the southern and southeastern parts of the city.

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Friday is the busiest day, with 222,500 trips, while Sundays saw only 129,000 trips.

San Francisco officials want to gauge Uber’s and Lyft’s impact on the city. That’s why the transportation authority, which is distinct from the San Francisco Municipal Transportation Agency, produced the report. It was based on data collected from the companies’ apps by Northeastern University researchers over a six-week period late last year.

“Information is power,” said Supervisor Aaron Peskin, who chairs the authority, describing the findings as “shocking” news. “This information will be used by me and my colleagues, and hopefully members of the state Legislature to ... take policy steps to rationalize this new frontier.”

Uber and Lyft are regulated at the state level by the California Public Utilities Commission, while taxis are regulated by cities or counties. (In San Francisco, the SFMTA regulates taxis.) Peskin hopes the Legislature will allow cities like San Francisco where the services’ impact is acute to create “a certain amount of reasonable regulation.” He pointed to Supervisor Jane Kim’s suggestion of a per-ride fee as an example.

“Increasing ride-sharing is one of San Francisco’s stated transportation priorities, and we stand ready to work with the city to update its infrastructure to reflect its transportation goals,” Uber said in a statement, noting that it has not seen the report. Lyft declined to comment.

Both Uber and Lyft refuse to share usage information and have persuaded the California Public Utilities Commission to keep it private. San Francisco City Attorney Dennis Herrera last week subpoenaed Uber and Lyft for their data and asked the state commission to provide records as well. The commission on Monday said it will discuss whether it should make ride-hailing information available to the public and to government entities.

The transportation authority’s report underestimates ride-hailing because it only looks at trips that start and end in San Francisco, excluding San Francisco International Airport trips and other destinations and origins outside the city. According to SFO authorities, there were 615,851 Uber and Lyft trips to and from the airport in April, the most recent month for which data are available.

The county transportation authority plans to continue with reports that zero in on public-transit impacts, disability access and how many passengers are in the cars. Uber and Lyft often point to their shared-ride options, UberPool and Lyft Line, as a way they help ease congestion, with both saying that those account for almost half of local trips.

Peskin said the companies should be more forthcoming with hard numbers.

“If Uber wants to break bread with the city of San Francisco, they should fork over the rest of the data we need: regional trips, accessibility, occupancy,” he said. “If they want to keep making UberPool claims, then prove it to us.”

Carolyn Said is a San Francisco Chronicle staff writer. Email: csaid@sfchronicle.com Twitter: @csaid

How many Ubers and Lyfts are there?

All numbers are for trips that start and end in San Francisco, excluding San Francisco International Airport trips and other destinations or origins outside the city.

170,000 Uber/Lyft local trips on typical weekday

570,000 vehicle miles driven by Uber/Lyft cars on typical weekdays

5,700 Uber/Lyft cars on city streets at peak (6:30-7 p.m.) on weekdays

6,500 Uber/Lyft cars on city streets at peak (7:30-8 p.m.) on Fridays

Source: San Francisco County Transportation Authority

How did they count them?

Researchers at Northeastern University divided the city into 200 sections and used software to activate the Uber and Lyft apps every five seconds, which returned information on where vehicles were located. By observing changes in the supply of vehicles, researchers determined when drivers dropped off or picked up passengers, and started or ended a shift. The researchers said the activity did not affect drivers or riders. The County Transportation Authority cleaned and analyzed the data.

Research took place from Nov. 12 to Dec. 20, excluding the Thanksgiving holiday week because it was unusually busy. The report only looks at trips that started and ended in San Francisco, so it may underestimate usage.