You have mounted twin tyres on your truck tractor. What must you remember?

The selected combination of answers is correct because it addresses two important regulations related to the use of twin tyres on truck tractors.

1. The requirement for additional lights when the tyres extend laterally more than 40 cm ensures that other road users can see the vehicle clearly, especially in low visibility conditions. This is crucial for safety.

2. Marking the excessive width with warning plates is necessary if the overall width of the truck tractor exceeds 2.75 m due to the twin tyres. This ensures that the vehicle is compliant with regulations regarding width and helps prevent accidents by alerting other drivers to the vehicle's larger dimensions.

Both of these points are vital for adhering to German traffic laws, which emphasize safety and clear communication on the road. The third option regarding a maximum width of 2.55 m is not applicable when using twin tyres, as the regulation allows for wider vehicles in certain circumstances but still requires proper marking and lighting for safety.