You’re not insane: Traffic in San Francisco got a lot worse between 2010 and 2016, according to a new report from the San Francisco County Transportation Authority. When you really think about it, that makes a lot of sense. Seventy thousand people and 150,000 new jobs arrived in that time, and all of those people had to get places, and regularly.

But the report also points to other culprits: Uber and Lyft. Using data from the traffic analytics company Inrix, plus modeling that the agency says helped it establish a “counterfactual”—what might have happened in the city had the ride-hail companies not come to town—it concludes that these companies and their ride-hailing brethren contributed mightily to San Francisco’s growing traffic problem.

The report (which we've embedded below) concludes that Uber and Lyft were responsible for 51 percent of the daily vehicle delay hours increase between 2010 and 2016. (That’s one measure of extra hours spent in the car due to congestion.) During the same period, the report concludes, the companies accounted for 47 percent of the increase of vehicle miles traveled, and 55 percent of the average speed decline on roadways. Population and employment growth, plus changes in the road network, accounted for the other delays.

A map of San Francisco showing the change in vehicle delay hours. The sections in yellow show roads where delays decreased by 30 percent or less; the areas in dark purple show the roads where delays increased by 120 percent or more. San Francisco County Transportation Authority

That sounds really bad. And maybe just right to anyone who’s seen a car stop traffic to let off or pick up passengers. But the report is missing some crucial data, and it comes with a few caveats. For one, it doesn’t have exact information on the growth of freight and delivery during the period—exactly the period when the ranks of Amazon Prime members swelled exponentially, and services like grocery delivery became part of many people’s routines. And it doesn’t have information on construction in the region, which could also have contributed to traffic slowdowns.

Both ride-hailing companies criticize the report’s methodology. In a statement, a Lyft spokesperson called the report “flawed and an incomplete picture of the transit challenges San Francisco faces,” and said it would like to work with the county to implement traffic solutions like congestion pricing. An Uber spokesperson says the “study fails to consider critical factors like the spike in tourism or the growth of freight deliveries, both of which have exploded since the study’s baseline date of 2010.”

Uber and Lyft each say they would be willing to work with the county agency on plans to generate funding and support for transit. And both have touted their own recent forays into non-car transportation. Uber bought e-bike-share company Jump and is pushing into e-scooters. Lyft bought large American bike-share operator Motivate and has introduced scooters in Denver and Santa Monica, California, this fall.