If the Colorado Public Utilities Commission has been fair in issuing tens of thousands of dollars in fines, three Denver cab companies have been allowing their drivers to work too hard in recent months.

Denver Yellow Cab, Metro Taxi, and Freedom Cab are accused of violating—on multiple occasions—the so-called “80 in eight” rule, which is intended to prevent drivers from working more than 80 hours in any eight-day period, according to 9News. The source of the problem appears to be the drivers’ bottom lines. They’re working long hours to pay high lease fees to companies for their cabs.

“I’m paying $750 for four days out here,” says Yellow Cab driver Doug Place. “What the PUC needs to do is look at what the companies are actually charging their drivers.”

About 150 local drivers are seeking to open their own service, but their plan has been rejected by a judge, who has ruled that a new company would damage existing companies, reports Denver Daily News.