How far ahead should a driver typically look while driving, according to the AAMVA manual's visual search guidance?

49 CFR 383.111(a)(7) (Visual Search); AAMVA CDL Manual Section 2.4.1, p.2-10, Fig 2.6

Looking only a few seconds ahead means reacting to hazards instead of anticipating them, which is especially dangerous in a vehicle that takes much longer to stop than a car. The 12-15 second benchmark gives enough lead time to change lanes, slow down, or plan around a developing situation smoothly. This scanning habit is foundational to the entire visual-search knowledge-test topic.