GeekWire reports today that Uber is planning to launch a new carpooling service in Seattle on Thursday.

The new option in the Uber app, called uberHOP, will take vehicles full of people between set points during morning and evening rush hours for a $5 flat rate per ride.

From GeekWire:

Uber Seattle GM Brooke Steger told GeekWire that for now, uberHOP will operate on three routes from 7 a.m to 10 a.m and 4 p.m. to 7 p.m.: Capitol Hill to downtown, Fremont to downtown, and Ballard to South Lake Union. uberHOP rides will also operate reverse routes, meaning downtown to Capitol Hill, downtown to Fremont, and South Lake Union to Ballard.

Riders who use the service will be picked up and dropped off at predetermined locations by UberXL vehicles, which carry up to six people.

Steger tells GeekWire “drivers will be guaranteed at least $35 per hour as Uber tests this new service in Seattle.” (Uber confirmed to The Stranger that this means the company will pay participating drivers that much even if no one uses the new service.)

The company already has another, slightly different carpooling service, UberPool, that's available in some other cities but not Seattle. Both services are part of Uber’s push to expand its carpooling options—an effort that highlights tensions over whether the ride-hailing app is worsening congestion in cities where it’s popular.

When top Uber advisor David Plouffe came to Seattle last week to talk about the “future of work” (and advocate against a bill allowing Seattle app-based drivers to unionize), he talked up carpooling as a way to cut down on congestion in cities like Seattle. Seattle manager Brooke Steger made the same case to GeekWire:

“We all know Seattle has huge congestion problems and there are limited ways for us to expand the current transportation network on the road,” she said. “Our goal is to pull people out of personal cars and encourage them to use alternative forms of transportation.”

That argument depends on the assumption that riders would otherwise be driving their own cars, rather than taking a bus, train, or bike. Leaders like New York Mayor Bill de Blasio have pushed back against Uber's claims, blaming the company for worsening traffic.

Seattle Mayor Ed Murray expressed similar concerns in October, according to the Puget Sound Business Journal, saying that "technology could actually make the problem worse unless we figure out managing it."