An autonomous vehicle startup backed by Ford Motor Co. F 1.22 % Chairman Bill Ford raised 16 million in additional funding with an eye on launching autonomous taxis in Singapore this autumn. One of the leading developers of self-driving technology, Cambridge, Mass.-based nuTonomy is racing heavyweights--including Uber Technologies Inc., General Motors Co. GM 1.14 % and Alphabet Inc. GOOGL 1.96 % --to further testing of autonomous cars on public roads. The company was spun out of the Massachusetts Institute of Technology in 2013, and counts Highland Capital Partners LLC and Singapore's economic development arm among its investors. In January, it raised 3.6 million from a group of investors that included Mr. Ford's venture-capital firm, Fontinalis Partners. NuTonomy Chief Executive Karl Iagnemma said the latest round is "going to let us accelerate our progress--more people and more cars."