Forward-looking statements made during this conference call speak only as of today's date, and the company undertakes no obligation to update them to reflect subsequent events or circumstances. Also, I would like to remind you that during the course of this conference call, we may discuss some non-GAAP measures in talking about the company's performance. We refer to adjusted EBITDA as a key bottom line measure of our performance.
There is a full reconciliation of the U.S. GAAP net loss to adjusted EBITDA on our press release, which can be found on the Investor Relations section of our website. Unless noted otherwise, all comparisons are versus the prior-year period. This conference call is also being broadcast on the internet and is available through the Investor Relations section of Zipcar's website.
So with these formalities out of the way, I'd now like to turn the call over to Scott Griffith. Scott, you may begin.
Scott W. GriffithThanks, Jonathan. Good afternoon, and thanks to everyone for joining us on today's call. Throughout the second quarter, we continued to expand our market leadership position within the car sharing category and the broader mobility services sector. We posted a solid double-digit increase in revenue while expanding our margins and growing into new geographies. Driving these gains is a compelling value proposition that continues to resonate with our more than 730,000 members globally. Zipcar represents a convenient and affordable alternative to car ownership in dense urban areas where costs are high and personal cars sit idle more than 90% of the time. We also provide effective mobility solutions for small and medium-sized businesses, government agencies and university communities, all of which are rapidly increasing their adoption of the car sharing model to meet their transportation needs with sensible, cost efficient alternatives. With a clear leadership position, a loyal membership base and continued technology and services innovation, we remain energized and excited to stay at the forefront of car sharing and mobility services. In a few minutes, I'll outline how we envision leveraging our brand, technology and network advantages in the future.