A large part of the Dutch motorways is equipped with variable message signs (VMS). They can show the maximum speed. The old VMS type (3.6) presents the maximum speed without a red ring. However, in the future all speed limits must have a red ring and should therefore be replaced by a new VMS type (3.7.2). A less expensive alternative is to modify the existing 3.6 VMS to a sign with a red ring (3.6RR). The three VMS types have different dimensions. Therefore, the Netherlands Transport Research Centre (AVV) wants to know the legibility distances of these three VMS types, equipped with a light guide technology. AVV was also interested in the performance of a VMS matrix sign, equipped with light emitting diodes (LEDs) which can show normal traffic signs with limited resolution. In a field experiment the legibility distance was determined of the maximum speed images of 50, 70, 80, 90 100 and 120 km/h on the four VMS types. Subjects approached the VMS until they could read them, clearly and without doubt. Then the distance from the sign, the legibility distance, was noted. The results show that the 3.6 VMS has the largest legibility distance (158 m). On the second place is the 3.7.2 VMS (136 m), and on a shared third place are the 3.6RR VMS and the matrix sign (111 m). A large part of the legibility difference between the four VMS types can be explained by the differences in letter height. Another part can be explained by the negative influence of the red ring, especially in case of the 100 and 120 km/h images. The relatively close-fitting bright red ring of the 3.6RR VMS hampers the legibility of the letters on the VMS. Without red ring the legibility distance is 29% larger. It is concluded that all four VMS types are legible at such a distance that road users are able to react adequately and in time to the message on the VMS. For related work see C 23394 (ITRD E206642).
Samenvatting