The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Effects of Weather-Controlled Variable Message Signing on Driver Behaviour

Pirkko Rämä

Dissertation for the degree of Doctor of Science (Technology) to be presented with due permission for public examination and debate in Auditorium K 216 at Helsinki University of Technology (Otakaari 4, Espoo, Finland) on the 2nd of November, 2001, at 12 o'clock noon.

Overview in PDF format (ISBN 951-38-5872-3)   [555 KB]
VTT Publications 447, ISSN 1455-0849

Dissertation is also available in print (ISBN 951-38-5871-5)
Copyright © 2001 VTT Technical Research Centre of Finland
VTT Publications 447, ISSN 1235-0621


This study investigated the effects of local and frequently updated information about adverse weather and road conditions on driver behaviour. The information was transmitted by several types of variable message signs (VMS). Two evaluations investigated the effects of VMS systems involving an individual sign or two signs; two other evaluations focused on more extensive VMS systems involving several signs, and two evaluations studied the effects of the sign technology. The slippery road condition sign and minimum headway sign decreased the mean speed of cars travelling in free-flow traffic by 1-2 km/h. The minimum headway sign also decreased the proportion of short headways. In addition, drivers' reports suggested that these variable message signs have other effects on driver behaviour, such as the refocusing of attention to seek cues on potential hazards, testing the slipperiness of the road, and more careful passing behaviour. Lowering the speed limit from 100 km/h to 80 km/h on a weather-controlled road decreased the mean speed by an average of 3.4 km/h in winter. The system proved most effective when adverse weather and road conditions were not easy to detect. The system also decreased the standard deviation of speed. Most drivers accepted lowered speed limits and found variable speed limits useful. Variable speed limit signs using fibre-optic technology were found to be more effective than electromechanical signs. However, effective signs may divert the driver's attention from adjacent fixed signing. The slippery road condition sign is recommended for careful use at critical spots, whereas a system including variable speed limits is recommended for somewhat longer road sections. The use of fibre-optic signs is recommended for weather-controlled applications.

This thesis consists of an overview and of the following 6 publications:

  1. Rämä, P. and Kulmala, R. 2000. Effects of variable message signs for slippery road conditions on driving speed and headways. Transportation Research Part F, Vol. 3, pp. 85-94.
  2. Luoma, J., Rämä, P., Penttinen, M. and Anttila, V. 2000. Effects of variable message signs for slippery road conditions on reported driver behaviour. Transportation Research Part F, Vol. 3, pp. 75-84.
  3. Rämä, P. 1999. Effects of weather-controlled variable speed limits and warning signs on driver behavior. Transportation Research Record, 1689, pp. 53-59.
  4. Rämä, P. and Luoma, J. 1997. Driver acceptance of weather-controlled road signs and displays. Transportation Research Record, 1573, pp. 72-75.
  5. Luoma, J. and Rämä, P. 1998. Effects of variable speed limit signs on speed behaviour and recall of signs. Traffic Engineering + Control, Vol. 39, pp. 234-237.
  6. Rämä, P., Luoma, J. and Harjula, V. 1999. Distraction due to variable speed limits. Traffic Engineering + Control, Vol. 41, pp. 428-430.

Keywords: traffic signs, speed limit, variable message signs, VMS, cold weather, driver behavior, road condition, slippery, evaluation, information systems, winter, road surface, ice, traffic safety

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© 2004 Helsinki University of Technology

Last update 2011-05-26