If you are in an accident that involves another vehicle, providing that the cause of the accident was not illegal or intentional and within the terms and conditions of the car rental agreement, the driver will be liable to pay up to their rental vehicle excess amount.
As the owners of the rental car, the car rental company has full insurance for the vehicle and compulsory third party (CTP) insurance too to provide cover for vehicle owners and driver's legal liability where a car accident causes injury or death to other drivers, passengers, cyclists, motorcyclists or pedestrians.
So for example, if your rental vehicle excess is $5,000 and the rental car total value is $20,000, the driver would pay damages up to $5,000 and the car rental company's insurance would pay for damages to the rental car above $5,000.