Toyota Motor Corp. halted tests of its "Chauffeur" autonomous driving system on U.S. public roads after an Uber Technologies Inc. vehicle operating in autonomous mode under the supervision of a human safety driver struck and killed a woman in Tempe, Arizona, on Sunday evening.

"Because we feel the incident may have an emotional effect on our test drivers, we have decided to temporarily pause our Chauffeur mode testing on public roads," spokesman Brian Lyons said in an emailed statement, referring to its hands-off testing mode. The carmaker said it could not speculate on the cause of the crash or what it may mean to the future of the nascent automated driving sector.

Toyota had been doing on-road testing with self-driving vehicles in Michigan and California, Lyons said. The company has kept the number of vehicles small so they could be rapidly updated as the technology advances, he said, declining to name a specific number of self-driving vehicles in operation.