Rainvision: the impact of road markings on driver behaviour —— wet night visibility
Previous European research, i.e. COST 331 and the IMPROVER projects had demonstrated that road markings greatly increase driver comfort during dry night time conditions. Nevertheless, they highlighted the need for additional research under wet and wet and rainy conditions.
Building upon this research, the RAINVISION project has investigated over the last three years how road markings can influence driver behaviour under all nightime weather conditions (dry, wet and wet and rainy) and how different age groups and gender groups adapt their behaviour based on the visibility and retro-reflectivity of road markings. The project has carried out three different trials; i.e. a simulation trial in France, a track test trial in Austria and on-road trial in the United Kingdom in cooperation with local authorities. For the simulation and track test trials, more than 100 test subjects were recruited respectively according to three age groups (20–40, 41–60 and 61+ years) and took several trials during different conditions. For the on-road trials, 10 highrisk sites were selected in cooperation with Durham county and Type II marking materials were applied in these sections. The project subsequently monitored speed over a whole climatic cycle and undertook an accidentology analysis. The results of the study in general indicate that the presence of enhanced road markings did significantly increase driver comfort, especially for older drivers. While there was an increase in driver speed, it was not seen as safety hazard as it was compensated by greater preview times. In fact in the UK trials, the results show that the presence of enhanced road markings actually led to a decrease in speeds.
1.Previous research (e.g. COST 331,1991) and studies (IMPROVER, 2006) have confirmed that the night visibility of road markings is an essential contributor to driver comfort and road safety.
Nevertheless, road markings are often neglected, in many cases have even completely disappeared from roads. At the same time, as Europe’s population is ageing, the percentage of older drivers on Europe’s road is expected to increase significantly. Given that older drivers are more likely to have more accidents caused by to visual constraints than younger drivers, it is important to gain a better understand how core infrastructure elements such as road markings need to be adapted to serve the visual needs of a increasly ageing population. In this context, and capitalising on previous projects, RAINVISION studied the influence of road markings on driver behaviour, by mainly analysing how different age groups (young vs. middle vs. old) and different gender groups (male vs. female) adapt their driving behaviour on the basis of the visibility and retroflectivity of road markings under three weather conditions, (i.e. dry, wet, wet and rainy) during night time driving. To arrive at its conclusions, the project undertook three sets of trials, i.e. simulation driving in France, a track test in Austria and an on-road trial in the United Kingdom. This paper outlines the results of these three trials, offers some conclusions, highlights the limitations of the study and provides pointers for future research.
2.Simulation studies
2.1. Description oftrialsThe simulation trials were carried out on the premises of Aximum (who was the partner responsible for this trial)and COLAS (which is the parent company of Aximum). Both trials took place in the vicinity of greater Paris.A total of 123 subjects were recruited and tested as drivers on the driving simulator through several sessions(Table 1). The requirements for the recruitment were that people should be aged at least 20 years old, should havehold a class B driving license for a minimum of two years and should usually drive a vehicle on a daily basisSubiects were split into three age categories as shown below:
To avoid biased results, subjects had to undergo a series of visual tests: binocular acuity for long distance vision; stereoscopic vision; colour and contrast perception; mesopic vision and glare (vision recovery time). Subsequently, participants were asked to drive on a simulated rural single carriage way environment under two driving scenarios, i.e. one with standard markings and a second with enhanced markings. To determine the impact of the road markings on driver behaviour, the study assessed the number of run-off incidents during the trials, i.e. occasions where the vehicle would either deviate from the boundaries of the road either by crossing into the opposite lane or cross the edge line.
2.2. Results
A subsequent analysis of the results found that the number of errors committed by subjects when driving under the standard road marking scenario was 70% percent higher compared to the enhanced road marking scenario. When looking at the effect by age group, the results showed that the improvement in the visibility of road markings made a big difference in terms of driver comfort forthe groups 21–40 and 61+ years, but did not appear to have an impact for the intermediary age group 41–60 years.
3.Overal conclusionsrecommendations,lmitations and future research
The RAlNVISION project sought to advance the state of the art in road markings research by analysing theimpact of road markings on driver behaviour during three night time conditions and taking into consideration thevisual needs of an increasingly ageing population.
Of the three trials, the most comprehensive was the track test which allowed for in-depth analysis of severafactors relevant to the study, i.e. speed, lateral acceleration, participants’ perception of the different road markingsetc. This trial clearly demonstrated that applying retro-rellective pavement marking material has a positive efect onthe subjective feeling of safety of drivers, especially in adverse weather/driving conditions which were simulated inthis experiment. Under night-time und rainy driving conditions, the marking material ll (wet retro-reflectivematerial) ensured clear trajectories of the driving path, thus providing anticipatory stimuli of road environment andtaking substantial workload offthe driver.
These results were largely confirmed by the simulation trials which found that errors committed by drivers whenroad marking were less visible, inereased by 70%. However, the simulation software did not allow for a number olimportant parameters to be captured (e.g. speed, acceleration) which would have allowed for a more holisticassessment ofthe impact of better markings.Concerning the on-road trials, and as mentioned above, the results contradicted the findings of the two previoustrials given that average speed actually decreased after the installation of better markings and the number ofaccidents increased, even though an analysis of police records could not link this increase to better markings. Themain shortcoming of the on-road trials is that it was not possible within the budget allocated to the project toactually monitor the drivers driving patterns in detail - as is done in major Field Operational Tests (FOTs) orNaturalistic Driving (ND) studies-, which in tum would have given the project a more in-depth understanding of theimpact ofroad markings on driver comfort.
One of the core recommendations of the projects, which stems from the previous research results as well as anextensive literature review of existing practices on European roads, is to establish a intervention and maintenancestandard for road markings of 150 med/lux/m* (R3) during dry conditions and 35 med/lux/m" (RW2) for wet andrainy conditions, that should apply to all TEN-T and major A-roads. In addition, it recommends a minimum width of150 mm for these markings based on finding from Carlson et al.Such an intervention and maintenance standard is expected to provide an increasingly ageing driver populationsuflicient preview times to compensate for their reduced visual abilities. At the same, this recommendation has beenendorsed by EuroRAP as one that would also guarantee reliable operation of Lane
Departue Waming (LDWS)/LaneKeeping Assistance (LKA) Systems which are gradually being introduced in new vehicles.In terms of fiuture research, there is a need to perform additional research, mainly in the form of field studies(FOTand/or ND), to be able to arrive at a definitive intervention and maintenance standard for LDWS/LKA systems inorder to take advantage of the important safety gain that can be expected from the introduction of such systems.Current proposals have been based on extensive desk research, yet real-life information is needed to understand howsuch systems work under diferent weather conditions and how road markings can ensure their reliable performance
Rainvision: the impact of road markings on driver behaviour —— wet night visibility
Previous European research, i.e. COST 331 and the IMPROVER projects had demonstrated that road markings greatly increase driver comfort during dry night time conditions. Nevertheless, they highlighted the need for additional research under wet and wet and rainy conditions.
Building upon this research, the RAINVISION project has investigated over the last three years how road markings can influence driver behaviour under all nightime weather conditions (dry, wet and wet and rainy) and how different age groups and gender groups adapt their behaviour based on the visibility and retro-reflectivity of road markings. The project has carried out three different trials; i.e. a simulation trial in France, a track test trial in Austria and on-road trial in the United Kingdom in cooperation with local authorities. For the simulation and track test trials, more than 100 test subjects were recruited respectively according to three age groups (20–40, 41–60 and 61+ years) and took several trials during different conditions. For the on-road trials, 10 highrisk sites were selected in cooperation with Durham county and Type II marking materials were applied in these sections. The project subsequently monitored speed over a whole climatic cycle and undertook an accidentology analysis. The results of the study in general indicate that the presence of enhanced road markings did significantly increase driver comfort, especially for older drivers. While there was an increase in driver speed, it was not seen as safety hazard as it was compensated by greater preview times. In fact in the UK trials, the results show that the presence of enhanced road markings actually led to a decrease in speeds.
1.Previous research (e.g. COST 331,1991) and studies (IMPROVER, 2006) have confirmed that the night visibility of road markings is an essential contributor to driver comfort and road safety.
Nevertheless, road markings are often neglected, in many cases have even completely disappeared from roads. At the same time, as Europe’s population is ageing, the percentage of older drivers on Europe’s road is expected to increase significantly. Given that older drivers are more likely to have more accidents caused by to visual constraints than younger drivers, it is important to gain a better understand how core infrastructure elements such as road markings need to be adapted to serve the visual needs of a increasly ageing population. In this context, and capitalising on previous projects, RAINVISION studied the influence of road markings on driver behaviour, by mainly analysing how different age groups (young vs. middle vs. old) and different gender groups (male vs. female) adapt their driving behaviour on the basis of the visibility and retroflectivity of road markings under three weather conditions, (i.e. dry, wet, wet and rainy) during night time driving. To arrive at its conclusions, the project undertook three sets of trials, i.e. simulation driving in France, a track test in Austria and an on-road trial in the United Kingdom. This paper outlines the results of these three trials, offers some conclusions, highlights the limitations of the study and provides pointers for future research.
2.Simulation studies
2.1. Description oftrialsThe simulation trials were carried out on the premises of Aximum (who was the partner responsible for this trial)and COLAS (which is the parent company of Aximum). Both trials took place in the vicinity of greater Paris.A total of 123 subjects were recruited and tested as drivers on the driving simulator through several sessions(Table 1). The requirements for the recruitment were that people should be aged at least 20 years old, should havehold a class B driving license for a minimum of two years and should usually drive a vehicle on a daily basisSubiects were split into three age categories as shown below:
To avoid biased results, subjects had to undergo a series of visual tests: binocular acuity for long distance vision; stereoscopic vision; colour and contrast perception; mesopic vision and glare (vision recovery time). Subsequently, participants were asked to drive on a simulated rural single carriage way environment under two driving scenarios, i.e. one with standard markings and a second with enhanced markings. To determine the impact of the road markings on driver behaviour, the study assessed the number of run-off incidents during the trials, i.e. occasions where the vehicle would either deviate from the boundaries of the road either by crossing into the opposite lane or cross the edge line.
2.2. Results
A subsequent analysis of the results found that the number of errors committed by subjects when driving under the standard road marking scenario was 70% percent higher compared to the enhanced road marking scenario. When looking at the effect by age group, the results showed that the improvement in the visibility of road markings made a big difference in terms of driver comfort forthe groups 21–40 and 61+ years, but did not appear to have an impact for the intermediary age group 41–60 years.
3.Overal conclusionsrecommendations,lmitations and future research
The RAlNVISION project sought to advance the state of the art in road markings research by analysing theimpact of road markings on driver behaviour during three night time conditions and taking into consideration thevisual needs of an increasingly ageing population.
Of the three trials, the most comprehensive was the track test which allowed for in-depth analysis of severafactors relevant to the study, i.e. speed, lateral acceleration, participants’ perception of the different road markingsetc. This trial clearly demonstrated that applying retro-rellective pavement marking material has a positive efect onthe subjective feeling of safety of drivers, especially in adverse weather/driving conditions which were simulated inthis experiment. Under night-time und rainy driving conditions, the marking material ll (wet retro-reflectivematerial) ensured clear trajectories of the driving path, thus providing anticipatory stimuli of road environment andtaking substantial workload offthe driver.
These results were largely confirmed by the simulation trials which found that errors committed by drivers whenroad marking were less visible, inereased by 70%. However, the simulation software did not allow for a number olimportant parameters to be captured (e.g. speed, acceleration) which would have allowed for a more holisticassessment ofthe impact of better markings.Concerning the on-road trials, and as mentioned above, the results contradicted the findings of the two previoustrials given that average speed actually decreased after the installation of better markings and the number ofaccidents increased, even though an analysis of police records could not link this increase to better markings. Themain shortcoming of the on-road trials is that it was not possible within the budget allocated to the project toactually monitor the drivers driving patterns in detail - as is done in major Field Operational Tests (FOTs) orNaturalistic Driving (ND) studies-, which in tum would have given the project a more in-depth understanding of theimpact ofroad markings on driver comfort.
One of the core recommendations of the projects, which stems from the previous research results as well as anextensive literature review of existing practices on European roads, is to establish a intervention and maintenancestandard for road markings of 150 med/lux/m* (R3) during dry conditions and 35 med/lux/m" (RW2) for wet andrainy conditions, that should apply to all TEN-T and major A-roads. In addition, it recommends a minimum width of150 mm for these markings based on finding from Carlson et al.Such an intervention and maintenance standard is expected to provide an increasingly ageing driver populationsuflicient preview times to compensate for their reduced visual abilities. At the same, this recommendation has beenendorsed by EuroRAP as one that would also guarantee reliable operation of Lane
Departue Waming (LDWS)/LaneKeeping Assistance (LKA) Systems which are gradually being introduced in new vehicles.In terms of fiuture research, there is a need to perform additional research, mainly in the form of field studies(FOTand/or ND), to be able to arrive at a definitive intervention and maintenance standard for LDWS/LKA systems inorder to take advantage of the important safety gain that can be expected from the introduction of such systems.Current proposals have been based on extensive desk research, yet real-life information is needed to understand howsuch systems work under diferent weather conditions and how road markings can ensure their reliable performance
