Security cameras have been installed in some Bristol taxis as part of a trial project aimed at cutting down on violent and racist attacks.
Assaults on drivers have risen by almost 70% in the last year.
The compact camera unit deploys a wide angle lens so that images encompass the whole of the back of the cab.
Inspector Dave Bradnock of Avon and Somerset Police said: "If there's an incident then obviously the footage can be used as evidence."
The pilot scheme is being pioneered by the Safer Bristol Partnership and the campaign group SARI.
Bristol City Council is to pay for the cameras in about 20 taxis which will tape passengers' journeys using a recorder stored in the boot.
Taxi rates in the city have recently gone up because some drivers are refusing to work at night.
Cabbie John Elliot said: "I've been mugged three times, including once where they ran a Stanley knife down my hand."
In January, a South Gloucestershire taxi driver was attacked and killed in the Easton area of the city.