Evaluation of Driver Response to Arrow Boards of Varying Patterns

Abstract

To investigate potential impacts of various arrow board display patterns on traffic behavior, a semi-naturalistic study was conducted within a live work zone in Salem, Virginia. Specifically, the arrow board displays examined in the study were flashing arrow, sequential arrow, and sequential chevron patterns. The data collection site for the study was a work zone with a semi-permanent lane closure on Wildwood Road in Salem, Virginia, underneath the I-81 overpass at Exit 137. An arrow board was placed within a taper of traffic barrels in the left northbound lane, approximately 220 ft upstream of the work area. The taper redirected northbound traffic on Wildwood Road into the right lane while the arrow board displayed an appropriate pattern indicating the merge direction to oncoming vehicles. A standard 25-light arrow board was acquired and equipped with a data collection system that included a camera and radar sensor. The arrow board was then positioned into the existing work zone. The data collection system was programmed to automatically record video and radar data twice per day: 10:00 a.m. to 11:00 a.m. (i.e., morning) and 4:00 p.m. to 5:00 p.m. (i.e., afternoon). A different display pattern was used each week, with data collection occurring for five consecutive days (Sunday through Thursday) per display pattern. A supplemental data collection system was also placed upstream of the work zone to capture baseline speed data for traffic prior to when the arrow board was visible. Video from the arrow board was reduced to determine the number of vehicles in each lane as they approached the arrow board, as well as the distance at which vehicles merged from the closed lane into the open lane relative to the arrow board. Radar data from the arrow board was also reduced to isolate speed measurements to only vehicles traveling on Wildwood Road that ultimately passed the arrow board leading into the work zone. Vehicles that turned or entered from an intersecting street were excluded from analysis. Results of the study showed that time of day (i.e., morning vs. afternoon) had a significant effect on measures of traffic volume and lane occupancy rate. Traffic volume was found to be significantly higher during the afternoon (105 vehicles per 10 min) than in the morning (64 vehicles per 10 min). In contrast, the lane occupancy rate (i.e., the rate of vehicles traveling in the closed lane) was significantly higher in the morning (7.6%) than in the afternoon (5.1%). The arrow board display pattern was not significant for either traffic volume or lane occupancy rate. Neither the display pattern nor time of day had a significant effect on the distance at which vehicles changed from the closed lane into the open lane. However, the interaction between the two was approaching statistical significance (p = 0.07). Mean lane change distances ranged between 296 ft and 343 ft across all display patterns and times of day. However, an evaluation of the vehicle merge rate by distance revealed interesting differences among the display patterns. During the morning, the flashing arrow pattern consistently had the lowest proportion of vehicles using the closed lane at all distances, while the sequential chevrons had the highest proportion. During the afternoon, the sequential arrow had a consistently lower proportion of vehicles remaining in the closed lane across all distances, while the flashing arrow and sequential chevrons performed worse but similarly to each other.