Enlarge / Uber's current self-driving cars are based on the Volvo XC90. (credit: Uber) Four months after a fatal crash forced Uber to halt testing of its self-driving cars nationwide, the company announced Tuesday that it is resuming testing on Pittsburgh streets. But the announcement comes with an important caveat: initially, the cars will only be driven in "manual mode" with human drivers—not Uber's software—controlling them. "We're starting with cars in manual mode, with a Mission Specialist sitting behind the wheel and manually controlling the vehicle at all times," writes Eric Meyhofer, the leader of Uber's self-driving car program.