The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage. NEW YORK ( Trefis) -- Zipcar ( ZIP) has thrown a monkey wrench in the traditional car rental business over the last few years. The company currently serves over 600,000 members with a fleet of over 8,000 vehicles and is taking a decent chunk of the rental business from traditional rental companies like Hertz ( HTZ), Avis ( CAR) and car sharing services like Connect by Hertz, Enterprise's WeCar, UHaul's UCarShare and City Car Share. However the membership-based car sharing company now faces new competitors from up and coming low-cost, peer-to-peer (P2P) car sharing services like RelayRides and GetAround . Caught between rising competition from P2P sharing and big rental companies, Zipcar may suffer slower growth in its membership and usage over time. However we don't see this impacting valuation in the near term as Zipcar has plenty of growth opportunities in existing and new markets. In fact, we believe these new P2P services could be more complementary and encourage more people to consider car sharing programs over car ownership in dense urban population, which in the end could help Zipcar. We have a price estimate of $27.32 for Zipcar, about 60% ahead of the market price. See our complete analysis for Zipcar's stock here . With growing awareness and popularity, the car sharing market has recently witnessed the arrival of several P2P services like RelayRides, Getaround and Sprideshare and Jolly Wheels. While RelayRides has received funding from Google and August Capital, Getaround launched in May 2011 and recently won the TechCrunch "Disrupt NYC" award. By investing in smart web interfaces, smartphone apps and car-kits to enable keyless entry, P2P players like RelayRides and GetAround are making credible attempts to match the Zipcar's accessibility and convenience, with the cost advantage of not needing to purchase or rent a fleet. For example, RelayRides operates an online marketplace for P2P car sharing. Participating car owners install an OnStar car-kit that leverages tracking of vehicles and allows users to unlock cars using mobile phones. While the car-owner gets to keep 65% of the fee, RelayRides keeps a 15% cut and the remaining 20% goes to insurance costs.