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Review of the effectiveness of vehicle activated signs
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.
2013 (English)In: Journal of Transportation Technologies, ISSN 2160-0481, Vol. 3, no 2, 123-130 p.Article in journal (Refereed) Published
Abstract [en]

This paper reviews the effectiveness of vehicle activated signs. Vehicle activated signs are being reportedly used in recent years to display dynamic information to road users on an individual basis in order to give a warning or inform about a specific event. Vehicle activated signs are triggered individually by vehicles when a certain criteria is met. An example of such criteria is to trigger a speed limit sign when the driver exceeds a pre-set threshold speed. The preset threshold is usually set to a constant value which is often equal, or relative, to the speed limit on a particular road segment.

This review examines in detail the basis for the configuration of the existing sign types in previous studies and explores the relation between the configuration of the sign and their impact on driver behavior and sign efficiency. Most of previous studies showed that these signs have significant impact on driver behavior, traffic safety and traffic efficiency. In most cases the signs deployed have yielded reductions in mean speeds, in speed variation and in longer headways. However most experiments reported within the area were performed with the signs set to a certain static configuration within applicable conditions. Since some of the aforementioned factors are dynamic in nature, it is felt that the configurations of these signs were thus not carefully considered by previous researchers and there is no clear statement in the previous studies describing the relationship between the trigger value and its consequences under different conditions. Bearing in mind that different designs of vehicle activated signs can give a different impact under certain conditions of road, traffic and weather conditions the current work suggests that variable speed thresholds should be considered instead.

Place, publisher, year, edition, pages
Irvine, CA: Scientific Research Publishing, 2013. Vol. 3, no 2, 123-130 p.
Keyword [en]
Vehicle Activated Signs; Variable Message Signs; Threshold Trigger Value; Speed Variation; Traffic Volume; Mean Speed
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Komplexa system - mikrodataanalys, General Microdata Analysis - methods
Identifiers
URN: urn:nbn:se:du-11798DOI: 10.4236/jtts.2013.32012OAI: oai:DiVA.org:du-11798DiVA: diva2:602926
Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2016-05-30Bibliographically approved
In thesis
1. The Optimal trigger speed of vehicle activated signs
Open this publication in new window or tab >>The Optimal trigger speed of vehicle activated signs
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis aims to elaborate on the optimum trigger speed for Vehicle Activated Signs (VAS) and to study the effectiveness of VAS trigger speed on drivers’ behaviour. Vehicle activated signs (VAS) are speed warning signs that are activated by individual vehicle when the driver exceeds a speed threshold. The threshold, which triggers the VAS, is commonly based on a driver speed, and accordingly, is called a trigger speed. At present, the trigger speed activating the VAS is usually set to a constant value and does not consider the fact that an optimal trigger speed might exist. The optimal trigger speed significantly impacts driver behaviour.

In order to be able to fulfil the aims of this thesis, systematic vehicle speed data were collected from field experiments that utilized Doppler radar. Further calibration methods for the radar used in the experiment have been developed and evaluated to provide accurate data for the experiment. The calibration method was bidirectional; consisting of data cleaning and data reconstruction. The data cleaning calibration had a superior performance than the calibration based on the reconstructed data.

To study the effectiveness of trigger speed on driver behaviour, the collected data were analysed by both descriptive and inferential statistics. Both descriptive and inferential statistics showed that the change in trigger speed had an effect on vehicle mean speed and on vehicle standard deviation of the mean speed. When the trigger speed was set near the speed limit, the standard deviation was high. Therefore, the choice of trigger speed cannot be based solely on the speed limit at the proposed VAS location.

The optimal trigger speeds for VAS were not considered in previous studies. As well, the relationship between the trigger value and its consequences under different conditions were not clearly stated. The finding from this thesis is that the optimal trigger speed should be primarily based on lowering the standard deviation rather than lowering the mean speed of vehicles. Furthermore, the optimal trigger speed should be set near the 85th percentile speed, with the goal of lowering the standard deviation.

Place, publisher, year, edition, pages
Borlänge: Högskolan Dalarna, 2014
Series
Dalarna Licentiate Theses, 2
Keyword
optimal trigger speed, vehicle activated sign, vehicle mean speed, standard deviation, calibration, Doppler radar, driver behaviour, data analysis
National Category
Computer and Information Science
Research subject
Komplexa system - mikrodataanalys
Identifiers
urn:nbn:se:du-17538 (URN)978-91-89020-91-7 (ISBN)
Available from: 2015-05-26 Created: 2015-05-26 Last updated: 2015-06-15Bibliographically approved
2. 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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