Drivers encounter tens of signs in their daily trips. While many signs are well recognized by the drivers, many others are not. This study examines drivers' identification of 28 warning and regulatory signs. The identification rate was standardized as per sign exposure rate. Differences between nationalities are then tested. Questionnaires including these signs were distributed to 9000 drivers in Bahrain, Kuwait, Oman, Qatar, and United Arab Emirates. Over 4850 responded back (54%). The questionnaire illustrated the tested signs in color along with four selection choices. In order to have just comparisons between the drivers of the various nationalities, their educational background is controlled. Three best-identified signs by the drivers included those indicating slippery road, closed to motor vehicles and road narrows from both sides. The three least identified are those indicating not waiting, turn left ahead and turn left. The findings also showed the existence of functional problems in many regulatory signs. In fact, only one third of the signs are equally understood by Arab, Asian and Westerner drivers. The drivers poorly identified most of the signs included in this group. Furthermore, both Arab and Asian drivers identified another one third of the signs significantly less than Westerners. The signs in this group are generally well identified by the drivers. Regulatory signs indicating symbolic pictures caused greater comprehension difficulties to the drivers in this group. Finally, two thirds of the signs are poorly identified by Arab drivers compared with westerners. Warning signs are over-represented in this group.