Optimizing line spacing and width in grid road designs for shared space: An eye-tracking study of visual attention and safety

• Improved drivers’ pedestrian fixation, refixation intervals, total fixation time. • More balanced left–right fixation distribution on pedestrians across all lane widths. • Effective surface design can enhance quantity and spatial allocation of attention. Consistent and accurate visual attention to pedestrians is crucial for traffic safety. However, shared-space environments have raised concerns due to low vehicle yield rates, frequent near-miss incidents, limited awareness of pedestrian priority, and accessibility challenges for individuals with visual impairments. This study examines how line density (spatial arrangement and diagonal grid line count per unit area) affects drivers’ visual behavior in shared-space scenarios by introducing a novel metric, “refixation interval” (the time between consecutive fixations on pedestrians). It evaluates whether such designs can enhance drivers’ attention to pedestrians. Under three lane-width conditions (4.5, 6, and 9 m), we manipulated line density and linewidth, measuring drivers’ fixation counts on pedestrians, refixation intervals, total fixation time, and left–right fixation balance. Twenty participants (20–40 years) wore Tobii Pro Glasses 3 while randomly viewing 30 high-complexity road videos (35 s each). Each video presented 15 design conditions, shown twice per condition; all participants were exposed to all experimental conditions. We found that road designs with significantly superior gaze metrics had a road width-to-design spacing ratio of approximately 60 % and a linewidth-to-lane-width ratio of approximately 17 % ( p < 0.01). Optimal combinations shortened refixation intervals, increased fixation duration on pedestrians, and balanced left–right fixations, enhancing sustained attention. This proportional pattern remained consistent across roadways narrower than three lane widths. Therefore, this proportional relationship has broad practical application potential and can provide operational parameters for future shared-space design. This study bridges dynamic monitoring metrics with safety outcomes and advances road design theory.