PURPOSES : This research is to evaluate the effects of zig-zag marking. METHODS : Based on the literature review, This research adopt Comparison Group method which was developed by Hauer. RESULTS : The findings are as follows. Effectiveness of treatment at all site 1.06, intersection 0.92, median bus lane 1.93, school zone 0.50, below 6-lane 0.48, above 6-lane 1.19, cat vs person 0.57, car vs car 1.36, car only 1.29. CONCLUSIONS : Though the analysis, it was founded that zig-zag marking on the small scale road(below 6-lane) and school zone contribute to reduce traffic accidents(effectiveness of the treatment : 0.50, 0.48). But the accidents at large scale road and median bus lane where installed zig-zag marking demonstrated negative result.(effectiveness of the treatment indicates exceed 1.0).