a comparison of changeable message signals for motorways

five types of changeable message signals have been evaluated as part of the programme of research into motorway signalling at trrl. they were: (i) standard dtp matrix indicator type 410a; (ii) dtp signal as above but modified by the addition of a surrounding coloured ring; (iii) willings 'varicator' type w (roller-blind type); (iv) solari changeable road sign (roller-blind type); (v) 'multi-light' fibre-optic matrix signal. the characteristics assessed were legend recognition distance, reliability, constructional quality and costs. in daylight the recognition distances of the numerals as tested on the matrix and roller-blind signals were similar, but at night the latter were greater. in good visibility, numerals of a given size on the better of the two roller-blind signals would have had the longest recognition distance of the signals tested. this might be expected because the edges of the numerals were more clearly delineated than those on the matrix signals. arrows on the better of the two roller-blind signals could be seen further than arrows on matrix signals, probably because of their larger sizes and better definition. in reduced visibility the matrix signals had the better recognition distances. in most cases the signals had a recognition distance adequate for motorway speeds. the matrix signals were cheaper and more reliable than the roller-blind signals. overall, it was concluded that the internally illuminated matrix signals (eg of the dtp type) with white-on-black legends, with or without a surrounding coloured ring, would be the most suitable type of signal for use on motorways.(a)