The incident occurred in Ghat Ki Guni tunnel around 2.30 p.m. Sunday.
CCTV footages showed that the woman's husband and his four-year-old son beseeched passers-by for help for almost 10 minutes. However, no one stopped to help them, police said.
The survivor, Kanhaiyalal Raigher, tried to call relatives from his mobile, but failed as there was no network connectivity in the tunnel.
Raigher, a resident of a village on the outskirts of Jaipur, was on his way to his in-laws' house with his wife Guddi Devi, 26, daughter Arushi and son Tanish.
Guddi and Arushi died on the spot.
"The entry of two-wheelers is banned in the tunnel, which was inaugurated by Prime Minister Manmohan Singh and Congress president Sonia Gandhi Jan 19. However, two-wheeler riders flout this restriction to save time," said a police officer.
After driving for about 300 metres in the tunnel, Raigher overtook a truck, which later rammed into his motorcycle, the officer added.
"We saw the CCTV footages in which the truck involved in the mishap sped away, while Kanhaiyalal kept crying for help for 10 minutes. Several sports utility vehicles, cars and trucks passed by them. However, no one stopped to help the victims," said the officer.
An ambulance arrived when some employees involved in tunnel's maintenance called the police control room.