Metrobus services in Bristol could be withdrawn from parts of the city after a spate of attacks by vandals.
Bosses have threatened to suspend night-time services in Knowle West and Hengrove after m1 buses were targeted at the weekend.
In the incidents, bricks were thrown through the vehicle's windows- leaving the driver in a state of shock.
In a tweet, Metrobus said: “A number of journeys have had to be cancelled due to a high number of buses being vandalised over the weekend which are needing repair.”
The m1 route links the south of Bristol to Cribbs Causeway in the north and is used by hundreds of commuters every week.
But the firm has warned services could be suspended - or withdrawn altogether - if the attacks continue.
A spokesperson for Avon and Somerset Police said: "Enquiries are ongoing following two reports of criminal damage to buses in Bristol over the weekend.
"Thankfully, no-one was hurt in either incident. We are keeping an open mind as to whether they may be linked.”