Painting a yellow center line at blind curves on a busy multiuser path (bicyclists, pedestrians, in-line skaters, runners) decreased the percentage of people who "went the wrong way" on the path, in a before-and-after study whose sample size was 2,147. A busy 3.6-m (12-ft) paved recreational and commuting path in Philadelphia circles the Schuylkill River for 13.5 km (8.4 mi). There are numerous blind curves caused by hedges, rock outcrops, and bridge piers. Many people were traveling on the wrong side around sharp blind curves. Counts were taken and videotapes made in order to determine the percentage of bicyclists, pedestrians, in-line skaters, and runners on the proper side, on the wrong side, and passing on the wrong side. Then a solid-yellow center line and directional arrows were neatly spray painted at the blind curves, and after counts were taken. The percentage of wrong-side travel fell from 35% to 15%, a 57% reduction. White lines and arrows were placed at driveways and road crossings. The white lines reduced wrong-way travel from 30% to 10%, a reduction of 66%. Painted center lines kept people on the proper side and reduced the likelihood of conflicts and crashes. Paint is easy, fast, and inexpensive, and creates no physical obstacle; it is hard to damage and it works without education of the public.