Select members of the public will be able to hail a free ride through their smartphones in taxis operated by nuTonomy, an autonomous vehicle software startup. While multiple companies, including Google and Volvo, have been testing self-driving cars on public roads for several years, nuTonomy says it will be the first to offer rides to the public. The cars — modified Renault Zoe and Mitsubishi i-MiEV electrics — have a driver in front who is prepared to take back the wheel and a researcher in back who watches the car's computers. NuTonomy, a 50-person company with offices in Massachusetts and Singapore, was formed in 2013 by Iagnemma and Emilio Frazzoli, Massachusetts Institute of Technology researchers who were studying robotics and developing autonomous vehicles for the Defense Department. Auto supplier Delphi Corp., which is also working on autonomous vehicle software, was recently selected to test autonomous vehicles on the island and plans to start next year. An Associated Press reporter taking a ride Wednesday observed that the safety driver had to step on the brakes once, when a car was obstructing the test car's lane and another vehicle, which appeared to be parked, suddenly began moving in the oncoming lane. The company hopes its leadership in autonomous driving will eventually lead to partnerships with automakers, tech companies, logistics companies and others.