The crash came during the height of nationwide celebrations, with the biggest parades in Cologne, Dusseldorf and Mainz.
All other carnival parades in the central state of Hesse were ended on Monday as a precaution.
Hesse state is still reeling from a racist shooting last week in the Frankfurt suburb of Hanau. A 43-year-old man killed nine people with immigrant backgrounds late on Wednesday before killing his mother and then himself.