The length of roadway or waterway a person can see ahead.

"Length" matters because sight distance is measured, not guessed. In crash analysis, it can be estimated from photographs, scene measurements, road design records, vessel position, weather, lighting, and objects that block a view, such as curves, hills, parked vehicles, vegetation, bridge structures, or glare. "Can see ahead" also has a practical meaning: not what might be visible in perfect conditions, but what was actually visible to a reasonably attentive driver, rider, or operator at the time. Rain, fog, darkness, and muddy or flood-damaged conditions can sharply reduce it. In Maryland, severe flash flooding like the catastrophic Ellicott City events in 2016 and 2018 shows how fast visibility and surface conditions can change.

For an injury claim, sight distance often helps answer whether a person had enough time and space to perceive a hazard and react. That can affect arguments about negligence, causation, speed, lane changes, passing, stopping distance, or failure to keep a proper lookout.

It also matters because Maryland follows the strict rule of contributory negligence. If the evidence suggests an injured person could and should have seen the danger in time but failed to respond reasonably, that issue may become central to liability and damages.