Facilitating bicycle travel using innovative intersection pavement markings

In an effort to facilitate bicycle travel through intersections, newer traffic control devices have been applied, including the bike box (a space for bicycles to stop on a red signal ahead of the motor-vehicle stop bar) and the two-stage turn queue box (a space where turning bicyclists can wait before making the second stage of a two-stage turn). This study evaluated the effects of two bike boxes and two turn boxes installed in 2014 at an intersection in Charlottesville, Virginia.

Videos collected during three days before the changes (non-consecutive over a one-month period), and five days after the changes (non-consecutive in the fall and spring seasons) provided volume counts and tallies of traffic infractions and conflict events such as near-misses. Data were prepared in order to pair the before and after periods, resulting in eight 12-h sets of observations starting at 7:30 a.m., each with 48 time intervals of 15 min. Histograms indicated that the data departed severely from a normal distribution (due to many 15-min intervals with no events), meaning a typical statistical test such as t-test was not appropriate, so the Wilcoxon signed-rank test was employed to compare the before and after periods. To take advantage of the paired structure of the data (i.e., before and after), a matched-pair version of the test was performed. Additional tests were performed after a partial re-review of data to examine observational variability concerns.

Results were mixed and indicated that rates of traffic infractions decreased for some types of infractions and for some intersection approaches but increased for others. Some bicyclists used the new markings properly, but some used them improperly or failed to use them.