Visual acuity, field of view, and where to place your gaze
Vision is the driver's most important source of information. Good driving depends on where you look, how early you scan, and how well you notice movement, signs and hazards in your peripheral vision. Darkness, glare, fog, rain and dirty windows reduce visual input. Speed also narrows your useful field of view — the faster you drive, the less time you have to see, understand and react.
For a B-licence, the minimum visual acuity is 0,5 with both eyes together (Transportstyrelsen regulations TSFS 2010:125), and at least 120° horizontal field of view. If you need glasses or lenses, they must be worn while driving. The law also requires windows, mirrors and lights to be clean and functioning. If you can't see enough — slow down or don't drive.
You're driving at dusk after light rain. The road surface reflects the headlights, and a pedestrian in dark clothing is hard to make out at a crossing. Correct look-ahead is at least 3 seconds — at 90 km/h that's about 75 metres. Slow down early, scan wide, expect poor contrast. Be ready to stop even if the crossing first appears empty.
A common miss is looking too close in front of the car. That leads to late reactions and weak planning. Another exam trap is thinking the vision requirement is only about the eye test — it's also about clean glass, correct lighting, reduced glare and active scanning. Place your gaze where the car will be in 3 seconds and you'll spot hazards earlier.