People who throw rocks at cars should face harsh penalties similar to terrorists, says a Darwin taxi driver following a series of attacks.

Police say three cars were hit by rocks thrown from a footbridge on Bagot Road early this morning.

Cabbie Phil Conners told the ABC his car was hit on Saturday night.

"But the one that concerned me was a cabbie I was talking to this morning at the end of my shift and he had a gaping hole in his windscreen on the passenger's side," he said.

"I really dread to think of what could have happened, what the consequences could have been if there was somebody sitting there."

He says rock throwers should be punished severely.

"What would have happened if there had of been somebody sitting there?" he said.

"I'd like to see them charged as terrorists of something because that's how you feel.

"You feel terrorised when something's hitting your car."

Northern Territory Transport Minister Gerry McCarthy says the Government introduced legislation to deal with the issue two years ago.

"Since then I've been advised that there have been 29 people that have been charged, and 11 convictions," he said.

"Now a conviction for this reckless behaviour can result in a prison sentence of up to four years.

"So that message is out there very clearly."