Uber has been steadily releasing a series of updates to its driver-side product as part of its ‘180 Days of Change’ campaign, which kicked off with the introduction of in-app tipping. One of those changes, introduced in late August, allowed drivers to set up to six ‘Driver Destinations‘ per day, up from just two previously. Now, it’s reverting that change in four of its largest U.S. markets, citing “increased wait times for rides” and “a few long pickups.”

In a communication to drivers obtained by TechCrunch, and confirmed as accurate by the company, Uber noted that while “drivers have been using them, a lot,” the experiment ended up resulting in ETAs that are “bad for riders and drivers,” which has an impact on the driver side in terms of trips available and earnings. These changes are for New York, Chicago, San Francisco and Seattle only, Uber notes, with six daily destinations still available in all other markets.

Uber explained in the note that regardless of how much testing it does prior to a feature’s release, the actual impact of said changes isn’t yet well understood until they’re out in the real world. The increase in daily Driver Destinations proved something Uber felt it was “truly necessary” to roll back, according to the note to drivers. As with any product with a reach the size of Uber’s, experimentation can seldom entirely predict impact in real use conditions.

Uber’s head of Driver Product Aaron Shildkrout has been fielding feedback from drivers on Twitter about the change all weekend, since it was, as Uber said, a very popular feature switch. Uber tells TechCrunch it’s working on alternate ways to improve flexibility for drivers in those four cities, despite finding that this particular change didn’t work as planned.