This report examines a temporary traffic management system implemented in association with a work zone in Copenhagen, Denmark. Dynamic message signs and traffic detectors were deployed on freeways surrounding the work zone to support dynamic route information at diversion points and the implementation of variable speed limits (VSL). The temporary system was deployed in response to expected increases in accidents and congestion as a result of a roadway expansion project on the Køge Bugt Motorway where four lanes were expanded to six lanes between summer 2002 and summer 2003. The road construction project involved several changes in road geometry within the work zone.
Variable Speed Limits
The variable speed limit system deployed as part of this project was implemented to the south of the work zone, enabling the adjustment of speed limits for northbound vehicles approaching the work zone during the morning rush. DMS were also deployed on the southbound portion of the freeway, allowing speed limits to be adjusted in response to recurring afternoon congestion at an interchange at the southern end of the study area.
The VSL system experienced considerable technical difficulties during the deployment which likely had a negative influence on the impacts of the system. Problems included displaying incorrect speed limits for up to 18 percent of the morning rush hour periods, and difficulties in responding to congestion during the afternoon peak periods (DMS signs going blank, or displaying incorrect speed limits).
Questionnaire responses supported these findings. Numerous complaints were documented in reference to the speed limits being set too low for prevailing traffic conditions. In addition, several respondents noted flaws in the speed limits displayed. The questionnaire also found that after the implementation of the variable speed limit system 46 percent of respondents felt safer, 4 percent felt less safe, and the remaining 50 percent did not feel any more or less safe.
Dynamic Route Information
The dynamic route information system experienced considerable technical and implementation difficulties that likely influenced the response of travelers to the posted messages. These included inaccurate estimates of the delays on the two routes and a complicated series of messages used to display delay information on the dynamic message signs.
The questionnaires distributed to travelers found that 80 percent of the motorists participating in the survey were favorably disposed to both the variable speed limits and dynamic route information signs. However, the comments received regarding the accuracy of the delay messages and the appropriateness of the posted variable speed limits indicated that both systems were currently operating unsatisfactorily.
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