Police say if drivers don't pull over when they're signalled, they usually don't know their age

It's believed five teenagers were in a car that fled police in Christchurch early on Tuesday morning.

Their vehicle crashed into another one, killing an innocent motorist.

Lawyer Deborah Manning and the Children's Commissioner have urged police to re-think pursuing young drivers.

But Assistant Commissioner Sandra Venables says it's not that simple.

She says anytime police go to stop a vehicle, it's difficult to ascertain people's age until they speak with them.