A belt conveyor having upper article-supporting belt rollers that are rotated rearward by rotating lower belt rollers only when the articles are slowed or stopped from advancing with the belt. As the belt advances in a direction of travel, the lower rollers rotate by contact with a bearing surface underlying the belt. The upper rollers have axles whose ends are retained in slots that slope downward in the belt's direction of travel. The slots provide the upper rollers a range of positions between a forward position out of contact with the rotating lower roller and a rearward position contacting the lower roller, which rotates the upper roller rearward relieving back line pressure on accumulated articles.