Poul Greibe - Academia.edu (original) (raw)

Papers by Poul Greibe

Traffic Safety on Two ContinentsPTRC Education and Research Services Limited, 2000

Accident Analysis & Prevention, May 1, 2005

The number of roundabouts has increased significantly in Denmark over the last two decades. The m... more The number of roundabouts has increased significantly in Denmark over the last two decades. The majority of roundabouts are single-lane roundabouts (used in rural and urban areas), but due to increasing traffic volumes, more and more roundabouts in rural areas are now being built as 2-lane roundabouts. In Denmark, the capacity of roundabouts is traditionally based on gap acceptance theory and a number of previous studies have measured critical gap and follow up times for varied types of roundabouts in order to set up a general capacity model to be used in Denmark. This presentation will mainly focus on 2-lane roundabouts and will be based on a new study from 2-lane roundabouts (mainly with “turbo design”) that was completed in 2008. The results from the study include new values for critical gap and follow up times to be used in 2-lane roundabouts. The study also re-estimates the values for passenger car units (pcu) for two different categories of heavy vehicles. The new pcu-values indicate that capacity of roundabouts is more influenced by heavy vehicles than previously expected. The study also estimates the effect on capacity from exiting vehicles (vehicles leaving the roundabout at the adjacent arm). It is well known, that high traffic volumes of exiting vehicles reduce the capacity of entering vehicles. The results indicate that the capacity is reduced by up to 20% in situations with high traffic volumes of exiting vehicles. Empirical data from observed capacity at 2-lane roundabouts have been used to test different theoretical and empirical capacity models. In general, the theoretical capacity models seem to have certain limitations when it comes to describing the observed data. Methods to overcome these limitations are sought and will be presented. Finally, an analysis of drivers lane use when entering roundabouts has been examined. The majority of entering drivers use the right lane (outer lane), even at high traffic volumes. It is assumed that better signing and marking might lead to a more balanced use of the entrance lanes, which could lead to higher capacity.

Proceedings from the Annual Transport Conference at Aalborg University

Evalueringen af det danske pilotprojekt med 20 ATK-standere (stærekasser) på 11 lokaliteter viser... more Evalueringen af det danske pilotprojekt med 20 ATK-standere (stærekasser) på 11 lokaliteter viser markante effekter på trafikanternes hastigheder, men også store variationer mellem lokaliteterne. Ud fra detektordata ses det, at gennemsnitshastighederne er reduceret (5-22 km/t) ved selve ATK-standerne, 85%-fraktilhastighed er typisk reduceret endnu mere, og andelen af trafikanterne, der ikke overholder hastighedsgrænsen, er faldet markant. Rejsehastigheder baseret på GPS-data viser, at effekten er størst lige ved standerne, og der stort set ikke kan måles en effekt i en afstand af mere end 1.000 m fra standerne. Erfaringsbaserede sammenhænge mellem trafikanternes hastigheder og ulykker viser, at de fundne effekter på hastighederne er så store, at de vil have en betydelig positiv effekt på antallet af ulykker ved ATK-standerne.

Nordic road & transport research, 1999

Projektets emne er "Uheldsmodeller for signalregulerede vejkryds" og hovedformålet har ... more Projektets emne er "Uheldsmodeller for signalregulerede vejkryds" og hovedformålet har været at bruge Generaliserede Lineære Modeller (GLM) til beskrivelse af det forventede antal uheld i vejkryds. Det har endvidere være tanken at finde effekten af, at inddrage bløde trafikanter samt trafikkens svingbevægelser som forklarende variable i uheldsmodeller. Desuden er der afprøvet en mikromodel for 410-uheld.

Undersøgelsen omhandler uheldsrisikoen i kryds beliggende på strækninger med forskellige hastighe... more Undersøgelsen omhandler uheldsrisikoen i kryds beliggende på strækninger med forskellige hastighedsgrænser. Kun 4-benede signalregulerede kryds er medtaget. Alle krydsene (ca. 500 stk) er opdelt i 7 grupper, afhængig af om krydset er beliggende i by- eller landområde, og af den tilladte hastighed i krydsets hovedretning. Derefter er uheldsrisikoen beregnet for hver af disse 7 krydsgrupper. Uheldsrisikoen er beregnet både som uheldsfrekvenser og vha. regressionanalyser. Resultaterne viser, at risikoen er stigende for større tilladt hastighed. Især er antallet af dræbte og tilskadekomne stigende. 80 km/t kryds er signifikant mere uheldsbelastede end andre kryds.

Uheldsmodel for bystrækninger er 2. del af projektet Uheldsmodeller for bygader. 1. del af pro-je... more Uheldsmodel for bystrækninger er 2. del af projektet Uheldsmodeller for bygader. 1. del af pro-jektet, som omhandler 3- og 4-benede kryds, er afsluttet og afrapporteret i Vejdirektorat notat 24. Formålet med denne 2. del af projektet, har været at formulere uheldsmodeller der kan beskrive det forventede antal uheld for bystrækninger. Dette er gjort ved at indsamle samhørende data om uheld, trafiktal og vejgeometri for vejstrækninger i byområde, og derefter prøve at beskrive en sammenhæng mellem uheldstætheden og trafikmænger/vejudformning. Paperet beskriver de foreløbige resultater af undersøgelsen.

Hovedformålet med projektet er at demonstrere praktisk brug af uheldsmodeller til bygader, som bl... more Hovedformålet med projektet er at demonstrere praktisk brug af uheldsmodeller til bygader, som blev udviklet i Vejdirektoratets regi i sen 90'erne. Projektets sekundære formål var, at undersøge hvorvidt og godt disse uheldsmodeller passer til et andet vejnet end det oprindelige, der ydermere har et nyere sæt data. Projektet er under afslutning, og ventes offentliggjort i efteråret 2002. Uheldsmodellerne er nærmere beskrevet i Håndbog i trafiksikkerhedsberegninger [Rapport 220, Vejdirektoratet 2001]. Uheldsmodellerne er baseret på oplysninger om kryds og strækninger fra en række kommuner. Modellerne beregner det forventede antal uheld i kryds og på strækninger i byområder med baggrund i parametrene; uheld, trafikmængder, omgivelser og vejgeometri. Uheldsmodellerne kan bl.a. bruges i forbindelse med udpegning af særligt uheldsbelastede steder, dvs. til sortpletudpegning, eller til at prædiktere antallet af uheld ved ændringer af trafiksystemet i byer.

Formålet med projektet er vha. en før- efterundersøgelse at undersøge den trafiksikkerhedsmæssige... more Formålet med projektet er vha. en før- efterundersøgelse at undersøge den trafiksikkerhedsmæssige effekt ved etablering af omfartsveje omkring byer. Projektet omfatter 19 forskellige omfartsveje i Danmark. Undersøgelsen er lavet som en uheldsundersøgelse, der dels ser på den trafiksikkerhedsmæssige effekt for den enkelte omfartsvej men også i en metaanalyse ser på den samlede effekt for de undersøgte omfartsveje. Da projektet endnu ikke er afsluttet beskriver dette paper bagrunden for projektet, metodevalg samt foreløbige resultater.

During the last decades roadside advertising has become a major and rapidly expanding industry. U... more During the last decades roadside advertising has become a major and rapidly expanding industry. Until the last decade, the extent of roadside advertising signs along rural roads has been strongly restricted in Scandinavian countries, mostly for safety reasons and aesthetic considerations. But growing pressure on road authorities caused by significant financial interests has resulted in a rapidly increasing number of advertising signs along rural roads. The signs are placed at roadsides with the purpose of capturing and keeping driver attention. When the driver's attention is captured, resulting in long eye glances in large horizontal angles away from the road, the time available for driver's response to avoid a crash if something unexpected occurs is reduced. In this perspective, it is relevant to ask whether roadside advertising signs influence driver attention to such an extent that it affects road safety. With the purpose of investigating, if and how, roadside advertisi...

With the purpose of investigating how LED-advertising signs (LED) affect drivers’ attention compa... more With the purpose of investigating how LED-advertising signs (LED) affect drivers’ attention compared to static signs and other kinds of distractors along roads, a new Danish empirical on-road study has been carried out by using an instrumented car equipped with a camera system to monitor eye movements. Speed behaviour was recorded by use of GPS and additionally a laser scanner was used for measurement of distances to vehicles ahead. In total, 16 different test drivers drove a test route making 228 drive pasts of different LED-advertising signs. The test drivers were not informed about the main purpose prior to the test drive. Eye track data verified whether the driver was glancing at the LED-advertising signs (the number of glances, glance duration and glance angles). Different algorithms for detection of driver distraction were used. Critical situations were identified and analysed in detail to uncover the identity of distractors. Driving in daylight were compared with driving in d...

During the last decades roadside advertising has become a major and rapidly expanding industry. U... more During the last decades roadside advertising has become a major and rapidly expanding industry. Until the last decade, the extent of roadside advertising signs along rural roads has been strongly restricted in Scandinavian countries, mostly for safety reasons and aesthetic considerations. But growing pressure on road authorities caused by significant financial interests has resulted in a rapidly increasing number of advertising signs along rural roads. The signs are placed at roadsides with the purpose of capturing and keeping driver attention. When the driver’s attention is captured, resulting in long eye glances in large horizontal angles away from the road, the time available for driver’s response to avoid a crash if something unexpected occurs is reduced. In this perspective, it is relevant to ask whether roadside advertising signs influence driver attention to such an extent that it affects road safety. With the purpose of investigating, if and how, roadside advertising signs a...

Bicycle traffic has increased in the large cities in Denmark over the last 10-15 years. Moreover,... more Bicycle traffic has increased in the large cities in Denmark over the last 10-15 years. Moreover, politicians wish to continue the growth making bicycling ac-count for an even larger share of the urban area transportation. Similar objectives are found in many other countries, which also invest in a better cycling infrastructure. One of the measures taken in Denmark and elsewhere is the construction of cycle tracks in urban areas, which provide the necessary space for bicycle traffic and decrease perceived risk among cyclists. At the same time, in Denmark the national objective is to reduce deaths and injuries in traffic, where cyclists currently account for approximately 20% of the total number of injuries reported by the police. To achieve these objectives on increased safe cycling, a well-functioning and well-developed infrastructure for bicycle traffic is required. In urban areas, junctions very often constitute a bottleneck in relation to cyclist passability. At the same time, t...

Transportation Research Procedia, 2016

Accidents at curves in rural areas are a major safety problem in all EU countries, as these accid... more Accidents at curves in rural areas are a major safety problem in all EU countries, as these accidents occur frequently and often cause serious personal injuries. The perception of horizontal curves are very difficult for all road users and serious safety problems often occur in situations where large differences exist between the operating speed on the upstream alignment and the design speed of a curve. A solution for solving this problem is to provide the drivers with the necessary information to estimate the design speed of the curve by use of signing and marking. In some EU countries, guidelines exist stating how to apply signing measures at curves. But the guidelines differ. Besides this there are, for example in Denmark, a mixture of how identical curves actually are signed and marked. In this research project a framework is made for the process on how to classify horizontal curves on rural roads into five danger categories. In addition a purpose for a basic signing and marking concept is developed for each danger category, which has been tested in two EU countries. The aim of the framework is to develop a tool for local authorities, making them able to make signing and marking of horizontal curves in a structured and uniform way. The result should be that the road users always meet the same basic signing and marking in curves belonging to the same danger category and thereby have a better possibility to judge the danger of the curve. For the covering abstract, see IRRD E101115.

Traffic Safety on Two ContinentsPTRC Education and Research Services Limited, 2000

Accident Analysis & Prevention, May 1, 2005

Proceedings from the Annual Transport Conference at Aalborg University

Nordic road & transport research, 1999

During the last decades roadside advertising has become a major and rapidly expanding industry. U... more During the last decades roadside advertising has become a major and rapidly expanding industry. Until the last decade, the extent of roadside advertising signs along rural roads has been strongly restricted in Scandinavian countries, mostly for safety reasons and aesthetic considerations. But growing pressure on road authorities caused by significant financial interests has resulted in a rapidly increasing number of advertising signs along rural roads. The signs are placed at roadsides with the purpose of capturing and keeping driver attention. When the driver’s attention is captured, resulting in long eye glances in large horizontal angles away from the road, the time available for driver’s response to avoid a crash if something unexpected occurs is reduced. In this perspective, it is relevant to ask whether roadside advertising signs influence driver attention to such an extent that it affects road safety. With the purpose of investigating, if and how, roadside advertising signs a...

Transportation Research Procedia, 2016