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Effectiveness of trigger speed of vehicle-activated signs on mean and standard deviation of speed
Dalarna University, School of Technology and Business Studies, Computer Engineering.ORCID iD: 0000-0001-6526-6537
Dalarna University, School of Technology and Business Studies, Computer Engineering.
Dalarna University, School of Technology and Business Studies, Computer Engineering.
Dalarna University, School of Technology and Business Studies, Construction.
2016 (English)In: Journal of Transportation Safety and Security, ISSN 1943-9962, Vol. 8, no 4, 293-309 p.Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

Excessive or inappropriate speeds are a key factor in traffic fatalities and crashes. Vehicle-activated signs (VASs) are therefore being extensively used to reduce speeding to increase traffic safety. A VAS is triggered by an individual vehicle when the driver exceeds a speed threshold, otherwise known as trigger speed (TS). The TS is usually set to a constant, normally proportional to the speed limit on the particular segment of road. Decisions concerning the TS largely depend on the local traffic authorities. The primary objective of this article is to help authorities determine the TS that gives an optimal effect on the Mean and Standard Deviation of speed. The data were systematically collected using radar technology whilst varying the TS. The results show that when the applied TS was set near the speed limit, the standard deviation was high. However, the Standard Deviation decreased substantially when the threshold was set to the 85th percentile. This decrease occurred without a significant increase in the mean speed. It is concluded that the optimal threshold speed should approximate the 85th percentile, though VASs should ideally be individually calibrated to the traffic conditions at each site.

Place, publisher, year, edition, pages
2016. Vol. 8, no 4, 293-309 p.
Keyword [en]
mean speed and standard deviation, trigger speed, vehicle-activated signs
National Category
Transport Systems and Logistics Vehicle Engineering
Research subject
Complex Systems – Microdata Analysis
Identifiers
URN: urn:nbn:se:du-21427DOI: 10.1080/19439962.2014.976690ISI: 000380365800001Scopus ID: 2-s2.0-84963593330OAI: oai:DiVA.org:du-21427DiVA: diva2:926604
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2016-08-26Bibliographically approved
In thesis
1. A data driven approach for automating vehicle activated signs
Open this publication in new window or tab >>A data driven approach for automating vehicle activated signs
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vehicle activated signs (VAS) display a warning message when drivers exceed a particular threshold. VAS are often installed on local roads to display a warning message depending on the speed of the approaching vehicles. VAS are usually powered by electricity; however, battery and solar powered VAS are also commonplace. This thesis investigated devel-opment of an automatic trigger speed of vehicle activated signs in order to influence driver behaviour, the effect of which has been measured in terms of reduced mean speed and low standard deviation. A comprehen-sive understanding of the effectiveness of the trigger speed of the VAS on driver behaviour was established by systematically collecting data. Specif-ically, data on time of day, speed, length and direction of the vehicle have been collected for the purpose, using Doppler radar installed at the road. A data driven calibration method for the radar used in the experiment has also been developed and evaluated.

Results indicate that trigger speed of the VAS had variable effect on driv-ers’ speed at different sites and at different times of the day. It is evident that the optimal trigger speed should be set near the 85th percentile speed, to be able to lower the standard deviation. In the case of battery and solar powered VAS, trigger speeds between the 50th and 85th per-centile offered the best compromise between safety and power consump-tion. Results also indicate that different classes of vehicles report differ-ences in mean speed and standard deviation; on a highway, the mean speed of cars differs slightly from the mean speed of trucks, whereas a significant difference was observed between the classes of vehicles on lo-cal roads. A differential trigger speed was therefore investigated for the sake of completion. A data driven approach using Random forest was found to be appropriate in predicting trigger speeds respective to types of vehicles and traffic conditions. The fact that the predicted trigger speed was found to be consistently around the 85th percentile speed justifies the choice of the automatic model.

Place, publisher, year, edition, pages
Borlänge: Högskolan Dalarna, 2016
Series
Dalarna Doctoral Dissertations, 4
Keyword
Optimal trigger speed, vehicle activated sign, mean speed, standard deviation, calibration, driver behaviour, data driven approach, automatic model
National Category
Computer and Information Science
Research subject
Complex Systems – Microdata Analysis
Identifiers
urn:nbn:se:du-21504 (URN)978-91-89020-96-2 (ISBN)
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-05-30Bibliographically approved

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CiteExportLink to record
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Citation style
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Language
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