This article explores the most appropriate arrangement (vertical, horizontal) and the frame of reference adopted by drivers (intrinsic, relative) as determinants of the comprehension of new traffic messages (e.g., congestion before arriving to Milan). Two specific cases for location (event-before-city, event-after-city) were tested following two layouts: H (horizontal, left-right) and V (vertical, bottom-up). Four comprehension tests carried out between 2006 and 2013 with 10,099 drivers in four countries (Italy, Netherlands, Spain, Sweden) were analyzed in a 2 (case: Before vs. After) × 2 (disposition: H, V) × 4 (Country) betweensubject design. The comprehension of the V variants (78.1%) exceeded the comprehension of the H variants (54.1%) in all the countries in the "before" case. In no country did the V or H variants come close to functional understanding in the "after" case. The results provided evidence of the preferred model and relative frame of reference as determinants of message understanding.