In a letter to employees on Friday (which can be viewed in full via a link at the bottom of this story), Scott Griffith said he will be stepping down as Zipcar's CEO. Taking his place is Mark Norman, Zipcar's current president and chief operating officer.

The letter was sent one day after Avis Budget Group announced it had completed its acquisition of Zipcar.

Griffith, who was with Zipcar just over 10 years, wrote:

"I’ve talked in the past about a concept called 'innovate yourself' – those times in life where one should turn inward and compare the person we are to the person we ultimately aspire to be. This is one of those times for me. As I’ve reflected on the future leadership needs, I’ve come to realize Zipcar will require a fully-committed leader to unlock the power of the merger over the next several years. After a thoughtful review of the company’s needs over the next several years, I’ve concluded it’s best if I step back and give someone else the opportunity to put the pedal down and take Zipcar to the next level."

He continued: "While I’m passing the baton and transitioning today to an advisory role, I will remain Zipcar’s biggest fan."

View the Griffith's letter in its entirety here.