During a headlight alignment procedure, which factor is least likely to impact the alignment?

The factor that is least likely to impact the alignment during a headlight alignment procedure is dirty headlight lenses. While dirty lenses can reduce the effectiveness of the headlights by dispersing or blocking light, they do not affect the actual alignment or aim of the headlights.

Headlight alignment is focused on ensuring that the beams of light are directed correctly, which typically involves adjusting the vertical and horizontal angles of the headlight fixtures. Factors such as a heavy load in the vehicle trunk can alter the vehicle's suspension and overall height, affecting the headlight’s aim. A sloping drive surface can also influence how the lights project in relation to the intended alignment targets. Low tire pressure impacts the ride height and potentially alters the vehicle's alignment, which can directly affect headlight aim as well.

In contrast, dirty lenses do not change the physical position or angle of the headlights; they simply impact the visibility of the light produced. Thus, while it's important for lenses to be clean for optimal light output, it does not play a role in the alignment process itself.