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The Optimal trigger speed of vehicle activated signs
Dalarna University, School of Technology and Business Studies, Computer Engineering.ORCID iD: 0000-0001-6526-6537
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 [en]
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: urn:nbn:se:du-17538ISBN: 978-91-89020-91-7 (print)OAI: oai:DiVA.org:du-17538DiVA: diva2:814168
Available from: 2015-05-26 Created: 2015-05-26 Last updated: 2015-06-15Bibliographically approved
List of papers
1. Review of the effectiveness of vehicle activated signs
Open this publication in new window or tab >>Review of the effectiveness of vehicle activated signs
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
Keyword
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:nbn:se:du-11798 (URN)10.4236/jtts.2013.32012 (DOI)
Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2016-05-30Bibliographically approved
2. Data based Calibration System for Radar used by Vehicle Activated Signs
Open this publication in new window or tab >>Data based Calibration System for Radar used by Vehicle Activated Signs
2014 (English)In: Journal of Data Analysis and Information Processing, ISSN 2327-7203, no 2, 11 p.106-116 p.Article in journal (Refereed) Published
Abstract [en]

The accurate measurement of a vehicle’s velocity is an essential feature in adaptive vehicle activated sign systems. Since the velocities of the vehicles are acquired from a continuous wave Doppler radar, the data collection becomes challenging. Data accuracy is sensitive to the calibration of the radar on the road. However, clear methodologies for in-field calibration have not been carefully established. The signs are often installed by subjective judgment which results in measurement errors. This paper develops a calibration method based on mining the data collected and matching individual vehicles travelling between two radars. The data was cleaned and prepared in two ways: cleaning and reconstructing. The results showed that the proposed correction factor derived from the cleaned data corresponded well with the experimental factor done on site. In addition, this proposed factor showed superior performance to the one derived from the reconstructed data.

Place, publisher, year, edition, pages
Scientific Research Publishing, 2014. 11 p.
Keyword
Vehicle activated signs, Doppler radar, vehicle velocity, experiment, calibration
National Category
Engineering and Technology
Research subject
Complex Systems – Microdata Analysis
Identifiers
urn:nbn:se:du-16267 (URN)10.4236/jdaip.2014.24013 (DOI)
Projects
Allmänt Mikrodataaanalys - transporter
Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2016-05-30Bibliographically approved

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