EXTRA INFORMATION ON DYNAMIC MESSAGE SIGNS: POSSIBILITIES AND EFFECTS

In this report, the possibilities of displaying extra safety information on Dynamic Message Signs (DMSs) are explored. The technical possibilities for placing extra information on the signs are looked at, and the road safety effects are examined. The information to be displayed can be divided into two categories: (1) incident information, such as warnings for approaching road works, wrong-way drivers, fog, slipperiness, wind gusts, and accidents; and (2) general advice, such as wearing seat belts, using direction indicators, and keeping distance. From a technical view point, the Matrix Signalling Installations (MSIs) would seem to be the most obvious means of displaying incident information. These panels can display very localized information, however there is a very limited number of messages that can be displayed. The MSIs could be accompanied by panels displaying a number of pre-programmed words. For displaying general advice, the Dynamic Route Information Panels (DRIPs) seem to be the most suitable. Compared with MSIs, much more complex texts can be shown. For displaying extra information on DRIPs, however, an adaptation of the control system is essential. It seems that displaying incident information, in the form of adjusted speed limits on MSIs, results in behavioural adjustments. These adjustments are greater if the lower speed limits on MSIs are accompanied by a panel explaining the reason for the lower limit. No experimental research of the relationship between displaying general advice on DMSs and road safety has been done. Observations of, and interviews with, car drivers seem to indicate that drivers do not pay much attention to the general messages. However, the extra information does not seem to have any negative road safety effects either.