OSE class A.501, also known as 500άρα (500ara, "Big 500"). or Καναδέζα (Kanadeza, "Canadian"), is a series of diesel-electric locomotives operated by TRAINOSE. This locomotive was built in 1974 at by MLW and was put into operation by OSE in 1975. Outwardly they resemble the class A.451 locomotive with the main difference that they are of higher power and have different appearance before rebuilding as they did not have an elevated head-on with steam heating boiler. This did not allow them to be used in passenger cars during the winter, although they had electric heating.