Daimler Truck’s Board of Management has appointed John O’Leary as the next president and chief executive officer of Daimler Trucks North America, effective April 1.

O’Leary will succeed Roger Nielsen as the head of DTNA’s brands Freightliner Trucks, Western Star Trucks, Thomas Built Buses, Freightliner Custom Chassis Corp. and Detroit Diesel Corp. Nielsen will retire April 30 after a 35-year career at Daimler, including the last four as its president and CEO.

Most recently, O’Leary served as the chief transformation officer for Mercedes-Benz Trucks in Germany. Previously, he also has served as president and CEO of Thomas Built Buses, senior vice president for the aftermarket business, and chief financial officer of DTNA.

"John O’Leary has more than 20 years of experience at DTNA and knows the North American commercial vehicle business like no other,” Martin Daum, president and CEO of Daimler Truck AG and member of the Board of Management, said in a press release.

Under Nielsen’s leadership, DTNA started several customer trials with the Freightliner eCascadia and eM2 and launched the Thomas Built Buses Jouley school bus to pave the way to CO2-neutral transport at DTNA. In addition, he renewed the Western Star product lineup and the vocational truck business.

Nielsen began his career in 1986 as a Freightliner manufacturing engineer responsible for wiring harness testing, followed by management positions in manufacturing and supply-chain-management. From 2001 to 20016, he served as chief operating officer.