This sign on a vehicle indicates what type of transport?

You answered correctly that this sign indicates the transport of waste. In German traffic rules, this white rectangular sign with a black "A" is used on vehicles carrying waste materials, especially those that need to be clearly identified for reasons like environmental safety and regulations. It helps other drivers and authorities recognize the type of cargo and handle the vehicle accordingly. This sign is different from those indicating hazardous materials or army transports, which have their own distinct markings. Knowing this helps you respond correctly to various vehicle markings on the road.