What must a motor vehicle's maximum speed, determined by its construction, be at least if you want to use this road?

This traffic sign indicates the start of a "Kraftfahrstraße" or motor vehicle road in Germany. To use this road, a motor vehicle must be capable of reaching and sustaining a speed of at least 61 km/h by its construction. This rule ensures that only vehicles fast enough to safely keep up with typical traffic can use these roads, enhancing traffic flow and safety. Since you selected 61 km/h, your answer is correct. In future similar questions, remember that 61 km/h is the minimum speed requirement for motor vehicle roads, but not for autobahns (which require 61 km/h as well).