Adaptations in driver deceleration behaviour with automatic incident detection: A naturalistic driving study

Silvia F. Varotto*, Reinier Jansen, Frits Bijleveld, Nicole van Nes

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Traffic congestion and crash rates can be reduced by introducing variable speed limits (VSLs) and automatic incident detection (AID) systems. Previous findings based on loop detector measurements have revealed that drivers reduce their speeds while approaching traffic congestion when the AID system is active. Notwithstanding these behavioural effects, most microscopic traffic flow models assessing the impact of VSLs do not describe driver response accurately. This study analyses the main factors that influence driver deceleration behaviour while approaching traffic congestion with and without VSLs. The Dutch VSL database was linked to the driver behaviour data collected in the UDRIVE naturalistic driving study. Driver engagement in secondary tasks and glance behaviour were extracted from the video data. Linear mixed-effects models predicting the characteristics of deceleration events were estimated. The results show that the maximum deceleration is high when approaching a slower leader, when driving at high speeds and short distance headways, and close to the beginning of traffic congestion. The minimum time headway is short when driving at high speeds and changing lanes. Certain drivers showed higher decelerations and shorter time headways than others. Controlled for these main factors, smaller maximum decelerations were found when the VSLs were present and visible, and when the gantries were within close proximity. These factors could be incorporated into microscopic traffic simulations to evaluate the impact of AID systems on traffic congestion more realistically. Further research is needed to clarify the link between engagement in secondary tasks, glance behaviour and deceleration behaviour.

Original languageEnglish
Pages (from-to)164-179
Number of pages16
JournalTransportation Research Part F: Traffic Psychology and Behaviour
Early online date2 Mar 2021
Publication statusPublished - Apr 2021

Bibliographical note

Funding Information:
This research was partially funded by the executive agency of the Dutch Ministry of Infrastructure and Water Management (Rijkswaterstaat), who provided the variable speed limit database of the Dutch motorway network. The authors are grateful to Rijkswaterstaat and to Ingrid van Schagen at SWOV Institute for Road Safety Research for insightful comments on the original report of this project. Finally, the authors thank four annotators for coding the video data.

Publisher Copyright:
© 2021 Elsevier Ltd

Copyright 2021 Elsevier B.V., All rights reserved.


  • Automatic incident detection
  • Driver behaviour
  • Glance behaviour
  • Linear mixed-effects models
  • Naturalistic driving


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