Industry leader Progressive Corp. recorded nearly twice the commercial auto liability premiums written as its closest competitor in the third quarter.

Progressive has been growing its commercial auto business aggressively since taking the top spot from Travelers Cos. Inc. several years ago. It reported a year-over-year increase of 59.43% in direct premiums written for the third quarter, following on the heels of more than 20% year-over-year growth in the second quarter.

Though Progressive is already the largest commercial auto writer in the U.S., President and CEO Susan Patricia Griffith during a third-quarter conference call said it has the brand and capacity to "really grow in that space."

Industrywide, commercial auto liability insurance premiums written rose 15.45% year over year in the third quarter.

Data from the period shows that some of the biggest names in personal auto are making big gains in the commercial market as well. Berkshire Hathaway Inc. and Allstate Corp. in particular made major strides in the rankings. The former climbed two spots year over year to fourth, while the latter rocketed to No. 13 from Nov. 27 as its direct premiums written more than doubled.

Allstate reaped the benefits of a previously announced partnership with Uber Technologies Inc., which had included Illinois, New Jersey and Wisconsin since March. On June 29, Allstate expanded the partnership to include commercial auto coverage in New York for all Uber rides originating outside of the five boroughs of New York City.

In a third-quarter earnings call, Allstate Vice Chairman Steven Shebik attributed "virtually all" of the written premium increase within commercial lines to the Uber partnership.

"We feel good about where that business is," he said, according to a transcript of his remarks. "And we would love to continue to grow that business over time. "

Click here for a template to review quarterly underwriting information for insurance companies. Quarterly underwriting information by line of business is available in Parts 1 and 2 of the NAIC quarterly statements filed by U.S. insurance subsidiaries. This information is also available in the U.S. Insurance Statutory Financials database in MIOffice. Click here for an instructional webinar on how to operate the P&C market share template, which allows detailed analysis by lines of business.