This report evaluates the effectiveness of retroreflective tape in enhancing the visibility of heavy trailers and reducing side and rear impacts by other vehicles during dark conditions. The analysis is based on a statistical examination of 10,959 crash cases investigated by the Florida Highway Patrol and the Pennsylvania State Police from 1997 to 1999. The tape is found to be quite effective, reducing side and rear impacts into trailers by 29 percent in dark conditions, with a 41 percent reduction in "dark-not-lighted" conditions. It is particularly effective in reducing injury crashes, reducing impacts resulting in fatalities or injuries by 44 percent. The report also estimates that the tape could save 191 to 350 lives, prevent 3,100 to 5,000 injuries, and avoid 7,800 crashes annually. The effectiveness of the tape is highest in dark conditions, where it significantly reduces impacts, but it is less effective during daylight. The study also examines the status of tape on trailers, noting that almost 50 percent of pre-standard trailers had the tape by 1999, and that the majority of the tape met or was similar to the NHTSA standard.This report evaluates the effectiveness of retroreflective tape in enhancing the visibility of heavy trailers and reducing side and rear impacts by other vehicles during dark conditions. The analysis is based on a statistical examination of 10,959 crash cases investigated by the Florida Highway Patrol and the Pennsylvania State Police from 1997 to 1999. The tape is found to be quite effective, reducing side and rear impacts into trailers by 29 percent in dark conditions, with a 41 percent reduction in "dark-not-lighted" conditions. It is particularly effective in reducing injury crashes, reducing impacts resulting in fatalities or injuries by 44 percent. The report also estimates that the tape could save 191 to 350 lives, prevent 3,100 to 5,000 injuries, and avoid 7,800 crashes annually. The effectiveness of the tape is highest in dark conditions, where it significantly reduces impacts, but it is less effective during daylight. The study also examines the status of tape on trailers, noting that almost 50 percent of pre-standard trailers had the tape by 1999, and that the majority of the tape met or was similar to the NHTSA standard.