This study evaluates a new sign to indicate carpool lanes. The new sign consists of a symbol denoting a driver with the "+2" text both positioned on a blue plane that indicates a lane. The design has been evaluated with respect to legibility and comprehensibility. Concerning legibility no problems are expected, even when the new carpool symbol is combined with other symbols indicating additional special purpose road users such as trucks. Based on an experiment conducted among 210 drivers in the Netherlands, it is concluded that the new sign is understood by only an unacceptably small number of them (14.8%). The most important problems are: (1) the erroneous interpretation of "+2": drivers tend to think this means that 2 or more individuals should be in the car while in fact at least 3 people should be in the car; (2) inadequate interpretation of the plane indicating the lane; and (3) the barely-to-comprehend combination sign indicating various special purpose groups. It is recommended to completely reexamine the problems involved in developing a carpool sign and a special purpose sign. The conditions for such an investigation are outlined. (A)
Abstract