Incidents between Straight-ahead Cyclists and Right-turning Motor Vehicles at Signalised Junctions

doi:10.1016/j.aap.2016.07.035

Accident Analysis & Prevention

Volume 105, August 2017, Pages 44-51

https://doi.org/10.1016/j.aap.2016.07.035 Get rights and content

Highlights

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Staggered stop lines do not seem to reduce the number of right-turn accidents.
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Staggered stop lines may reduce the number of right-turn accidents involving lorries.
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Most right-turn conflicts occur in the middle and the end of the green phase.
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Fast cyclists have a high relative risk of being involved in right-turn conflicts.
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The visibility of cyclists affects their relative risk of being involved in conflicts

Abstract

Accidents between right-turning motor vehicles and straight-ahead cyclists are one of the most common accident types leading to cyclist injuries at signalised junctions in Denmark. A before-after safety evaluation of applying staggered stop lines in 189 arms at 123 signalised junctions is presented. The evaluation accounts for long-term accident trends and changes in motor vehicle traffic volumes. Applying staggered stop lines gives no decline in accidents between right-turning motor vehicles and straight-ahead cyclists. However, there is a statistical tendency to a decline of these right-turn accidents involving heavy vehicles. There are several questions about factors leading to right-turn accidents that cannot be answered by recorded accident data. A study of conflicting behaviour focuses on factors leading to conflicts. Video observations have been carried out in 10 arms at signalised junctions. A total of 45 situations with conflicting behaviour between right-turning motor vehicles and straight-ahead cyclists have been investigated and compared to a reference group of simultaneous arrivals. The relative risk is lowest when both parties stop on red before entering the junction. Upon simultaneous arrival of both parties at a green light, the relative risk is highest. Cyclists tend to have a higher relative risk of being involved in conflicts if they; a) ride through on yellow, b) have a time distance of at least 2 seconds to other cyclists, c) wear a black jacket, and/or d) arrive at the junction at a speed of at least 25 km/h. Much less can be said about the motor vehicles or their drivers on the basis of these video observations, but motor vehicles stopping in the cycle crossing in order to yield to pedestrians or cyclists have a higher relative risk of being involved in conflicts.

Introduction

Accidents involving right-turning and straight-ahead road users driving or riding in the same direction (accident code 312, see Fig. 1) accounted for 12% of injury accidents at signalised junctions in Denmark in 2001-2010 (Danish Road Directorate, 2011). This was the third most common accident situation at signalised junctions. In almost all of these right-turn accidents, the straight-ahead road user was a bicycle or a slow moped, while the right-turning vehicle was a passenger car in more than 60% of the accidents. The rest were primarily vans, lorries and busses. Most of the right-turn accidents occur at junctions on roads with cycle tracks or cycle lanes. Obviously, right-turn accidents are a great safety problem in Denmark, but may also be a prominent problem in other countries with many cyclists and bicycle facilities.

This paper presents results of two studies of accidents and conflicts between right-turning motor vehicles and straight-ahead cyclists/mopeds. The first study is a before-after safety evaluation of staggered stop lines at signalised junctions. The second study is a study of conflicting behaviour between right-turning motor vehicles and straight-ahead cyclists and mopeds also at signalised junctions. The first study prompted the second study.

Staggered stop lines (see Fig. 2) is a widely used application to prevent accidents between right-turning motor vehicles and straight-ahead cyclists/mopeds (right-turn accidents) in Denmark at signalised junctions. Another initiative is pre-green for cyclists. Pre-green is sometimes used in combination with staggered stop lines, especially when the staggering is less than 5 metres. Bike boxes also known as “advanced stop lines” are often used in other countries, but rarely at signalised junctions in Denmark. Abroad, bike boxes also facilitate cyclists’ left turn. This is not an option in Denmark, because cyclists are obliged by law to continue to the opposite corner of the junction before making the last part of the left turn no matter if there is a bicycle facility or not (sometimes this two-stage left turn is called “Copenhagen Left”). Common to these applications is that safety effects are achieved at the beginning of the green phase, when both parties (cyclist and motor vehicle) stop on red before entering the junction.

Based alone on accident data from Denmark, it is not possible to assess exactly when during the traffic signal phase accidents occur. To assess this, additional information related to accidents such as informative witness testimonies would be required. An accident study (Danish Road Directorate, 1987) shows that both parties stopped on red before entering the junction in 4 out of 39 observed right-turn accidents at signalised junctions with bicycle tracks. The study is based on a limited sample and is quite old. However, it was conducted before many safety measures preventing right-turn accidents were applied. Therefore, the study may suggest that the potential safety impact is no more than 10% for staggered stop lines and other safety measures targeting accidents at the beginning of the green phase.

The size of the right-turning motor vehicle often has an impact on the severity of the accident. Lorries were involved in 11 of 13 fatal right-turn accidents with cyclist in 2010-2012 in Denmark including 9 at signalised junctions (Danish Road Directorate, 2014). Studies from the Netherlands and Denmark indicate that the heavy vehicle had stopped on red prior to the right-turn accident in far more than 10% of the accidents (HVU, 2005, HVU, 2006, Schoon et al., 2008).

Right-turn accidents were grouped according to their time of occurrence in the green phase in a small study of the safety impact of staggered stop lines (Danish Road Directorate, 1994). At the beginning of the green phase, the reduction in right-turn accidents due to staggered stop lines was 90%, while the number of right-turn accidents in the remainder part of the green phase increased by 43% (totalling a non-significant decline of 35%). The study was based on a sample encompassing only 28 accidents and a short observational period. Furthermore, the study did not state whether both parties involved in the accident stopped on red before the accidents. In addition, it is unclear how junctions were selected for redesign and possibly a significant regression-to-the-mean effect due to selection bias was present. Other studies also indicate a decline in the number of right-turn accidents or conflicts (non-significant), but redesigns in these studies are characterized by being more comprehensive than just applying staggered stop lines (Jensen, 2002, Jensen and Nielsen, 1999, Linderholm, 1992, Newman, 2002).

Section snippets

Safety effect of staggered stop lines

The before-after safety evaluation is based on 123 signalised junctions with staggered stop lines in 189 of the arms applied in the years 1997-2009. The 123 junctions are located in five municipalities of which 106 junctions are located in the City of Copenhagen. The remainder 17 junctions are located in other large cities and suburbs of Copenhagen. No other modifications have been carried out at the junctions in connection with the application of staggered stop lines. This paper presents

Right-turn conflicts in signalised junctions

The safety evaluation of staggered stop lines gave rise to new questions related to the time of occurrence of right-turn accidents and the scenario preceding the accidents. A number of conditions cannot be investigated on the basis of accident data and therefore video observations have been used. Since accidents are relatively rare, observations of situations with conflicting behaviour between right-turning motor vehicles and straight-ahead cyclists/mopeds have been used. In connection with

Conclusions

The number of right-turn accidents in the before-after safety evaluation and the number of right-turn conflicts in the study of conflicts are not very high, only 110 and 45 respectively. The two studies may therefore not provide conclusions with good precision, but only indications and answers to more general questions.

The before-after safety evaluation indicates that staggered stop lines do not reduce the number of right-turn accidents, but they may reduce the number of right-turn accidents

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Bløde trafikanter udenfor signalregulering i vejkryds ?uheldsanalyse og adfærdsundersøgelse [Vulnerable road users with no obligation to follow signals at signalised junctions ?accident evaluation and evaluation of road user behaviour]

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Incidents between Straight-ahead Cyclists and Right-turning Motor Vehicles at Signalised Junctions

Highlights

Abstract

Introduction

Section snippets

Safety effect of staggered stop lines

Right-turn conflicts in signalised junctions

Conclusions

Højresvingskonflikter i signalregulerede kryds. Undersøgelse af konfliktende adfærd [Right-turn conflicts in signalised junctions. Investigation of conflicting behavior]

Sikkerhedseffekter af tilbagetrukne stopstreger [Safety effects of staggered stop lines]

Uheld mellem ligeudkørende cyklister og højresvingende bilister [Accidents between straight-ahead cyclists and right-turning car drivers]

Cyklisters sikkerhed i byer. Trafiksikkerhed og miljø. Rapport 10 [Cyclists’ safety in urban areas]

Temaanalyse. Ulykker i signalregulerede kryds 2001-2010 [Accidents in signalised junctions 2001-2010]

Årsrapport. Dødsulykker 2012. Rapport 466 [Fatal accidents 2012]

Højresvingsulykker med lastbiler og cyklister [Right-turn accidents between lorries and cyclists]

Ulykker mellem højresvingende lastbiler og ligeudkørende cyklister [Accidents between right-turning lorries and straight-ahead cyclists]

Mere sikker på cykel i Randers ?Før-og-efter uheldsevaluering. Notat nr. 5 [Safer on bicycles in Randers ?Before-after accident evaluation]

Udeladte signaler i Viborg ?Trafikantadfærd, trafikafvikling, kapacitet og konfliktende adfærd [No far side signals in Viborg ?Road user behaviour, trafic flow, capacity, and conflicting behaviour]

Bløde trafikanter udenfor signalregulering i vejkryds ?uheldsanalyse og adfærdsundersøgelse [Vulnerable road users with no obligation to follow signals at signalised junctions ?accident evaluation and evaluation of road user behaviour]