The woman was directing traffic for a security company, according to the police.
The exact cause of the accident is under investigation, the Ticino cantonal police wrote in a press release on Wednesday night. The truck was maneuvering in a road construction site.
The Swiss woman, who lived in the Bellinzona region, died of her serious injuries at the scene of the accident. According to the statement, the truck was being driven by a 53-year-old Italian man. A care team was called out to provide psychological support.