Shankar Lokesh Ramavat (49), his wife Manjubai (32) and six-year-old son Jamu died on the spot when the accident occurred at 4.15 pm.
The police said the family lived at Sanjay Gandhi Vasahat, Pashan. They said Shankar was a construction labourer.
The police said the three were on their way to Alandi Road when the accident happened. The police arrested the dumper driver, Haju Shaikh (21), a resident of Chicholi Mala, Kej taluka, Beed district.