Clearance lights detail which of the following areas of a vehicle?

Clearance lights are specifically designed to indicate the overall width of a vehicle, particularly for larger vehicles such as trucks and trailers. These lights are typically mounted on the top corners of a vehicle to ensure that they are visible to other drivers, signaling to them the vehicle's dimensions. This becomes especially important when considering the safe navigation of wider vehicles in various road situations, where other drivers need to be aware of the full extent of the vehicle to maintain clearance and avoid collisions.

The other options do not accurately reflect the function of clearance lights. For instance, while they do not indicate maximum height or overall length, which pertains to vertical clearance and the total size from front to back respectively, neither do they provide information about the registration number of the vehicle, which is not related to physical dimensions but rather identification.