Enlarge / Ola Källenius of Daimler AG. (credit: Christoph Schmidt/picture alliance via Getty Images) Daimler is planning to "rightsize" its spending on self-driving taxis, Chairman Ola Källenius said on Thursday. Getting self-driving cars to operate safely in complex urban environments has proved more challenging than people expected a few years ago, he admitted. "There has been a reality check setting in here," Källenius said, according to Reuters. He is just the latest executive to acknowledge that work on self-driving taxi technology is not progressing as fast as optimists expected two or three years ago.