Robbers cut the brakes on the car of a victim for whom they lay in wait, threatening to stab her when she pulled on the handbrake, police say.
The gang of three - including a brother and sister - have been jailed for a spree of violent robberies across Birmingham.
Women at bus stops were among the victims of attacks which happened between 31 May and 17 June.
They were jailed for 16 years between them after a two-and-a-half week trial.
Tyrone Cardin, 21, of Cowles Croft, Yardley; Rene Cardin, 19, of the same address; and Molly Evans, 19, of Larch Walk, Yardley, were convicted of four counts of robbery and one of assault with intent to commit robbery.
The women were jailed for five years and Tyrone Cardin for six years.
On 13 June, they severed the footbrake cables, the West Midlands force said, of a car parked in Edgbaston and lay in wait for its owner, a 57-year-old woman.
Handbag, phones and cash
When she returned to the vehicle and drove off, they struck when she used the handbrake to stop, threatening to stab her and stealing her handbag, phones and cash.
They next offended on June 17, targeting three victims on the same day.
Police said they intimidated a woman, 24 at a bus stop in Yardley into handing over her handbag and phone, then within minutes drove to another bus stop and pulled at a woman's handbag, driving off while holding on to it before letting go. They dragged the victim, 40, a short distance.
Later they targeted a 32-year-old woman at a bus stop in Small Heath, punching and kicking her to the ground before stealing her phone and bus pass.
On 31 May, they had ransacked a shop as a 16-year-old was locking up.
They were sentenced at Birmingham Crown Court on 15 December.