The extension is the result of work that refurbished stations between downtown and Old Town to accommodate the low-floor cars used on the route.The Green Line currently runs between Santee and the Old Town Transit Center. Passengers traveling to downtown or Petco Park currently have to switch to a Blue Line train."With the Green Line coming downtown, people all over San Diego can now reach the downtown area more conveniently," said Harry Mathis, the MTS chairman. "This event also marks about the half-way point in a major reinvestment of our trolley infrastructure, which will bring low-floor cars and modern stations to our entire trolley network."The more modern cars allows for quicker exiting and boarding, particularly for disabled passengers, which will mean faster rides for passengers, according to the MTS. The agency also believes that eliminating the Old Town transfer will shave 12 minutes off a trip from Mission Valley to Petco Park.The extension is one component of a larger, $720 million project to rejuvenate the entire trolley system, and is expected to be completed in three years. It will add 65 of the sleek low-floor cars the fleet, which currently has 11.The additional ones are scheduled to be added to the Orange Line -- from Santee to downtown -- next spring, and the Blue Line -- between Old Town and the border -- in 2014.The project is funded by a mix of the TransNet half-cent sales tax, bond proceeds and federal stimulus money.