Effecten van alcohol op rijgedrag: een gecontroleerde replicatie van de ervaringsproeg in het project "Alcoholvrij op Weg"

This report is about an experiment in which young drivers drove various rides in the instrumented vehicle of the Centre for Environmental and Traffic Psychology, with and without alcohol in a controlled experimental design. The experiment was carried out to validate the life-experience setup in the project “Alcohol-free on the road” in the south-east of the Dutch province Drenthe, and therefore had a comparable setup. “Alcohol-free on the road” is a an experience for young drivers in which they are confronted under strict surveilance and on a closed circuit with the effects of alcohol on driving behaviour. In this study the demonstration-setup is validated by a more structured and methodologically sound replication with more measures. Thus, the experience is embedded in the scientific body of knowledge about alcohol effects. The setup was as follows: on a closed circuit subjects drove two rides of five laps each, in which they had to drive through cone-gates, react to a traffic light, drive straight and manage curves. Each ride ended with a backparking manoeuvre into a cone-marked parking space. During the rides a driving instructor was present to judge the behaviour of the subjects on various aspects. In the instrumented vehicle various driving parameters were recorded. Supplementary a reaction task was performed with a duration of 20 minutes. Before and afterwards self-raing scales were answered. The addition of alcohol (wodka) to the beverages (orange juce) was kept as secret as possible for both subjects and judges. The results showed that driving behaviour was influenced by the use of alcohol, but not for all subjects in the same way. Some subjects drove more sloppy and more roughly, wereas others started to drive more careful, as to compensate the alcoholeffect which they apparently noticed. The judgements of the driving instructors and the driving parameters showed on various measures a significant difference between sober and alcohol, and in general there was a trend in the expected direction. Also in the self-rating measures and in the reaction task measures there were significant results. These results show that this setup effects are obtained that are comparable to known effects in the literature, and therefore that the life-experience setup of the original project “Alcohol-free on the road” is based upon scientific knowledge of the effects of alcohol on driving behaviour

Evaluation of legibility of not properly reflecting signs

in conditions of dew or temperatures below 0 degrees C the reflection of reflecting material on signs can be suboptimal. Problems with respect to legibility under such conditions were studied, as well as subjective ratings of the signed information. Images of the signs were presented using an LCD projector. Independent variables in the experiment were age, amount of information, stimulus quality, and presentation time. Dependent variables were errors in reproduction of the names of the cities, towns or villages on the signs, and subjective ratings. It turned out that all factors both separately and additively affected the amount of errors. Positive subjective ratings coincided mainly with level of reflection, and to a lesser degree with the amount of information, presentation time and familiarity of information. Relevance to industry: Different types of reflecting material have been developed to reflect light from signs optimally. Disadvantage of some of the materials is the effect dew and temperatures below 0 degrees C can have on reflection and legibility. The study has practical consequences in terms of novelty and amount of information to be presented on such a sign. (c) 2005 Elsevier B.V. All rights reserved

The consequences of an increase in heavy goods vehicles for passenger car drivers' mental workload and behaviour:A simulator study

The effects of an increase in Heavy Goods Vehicles (HGVs) on merging behaviour and on mental workload of motorists during filtering in and out of traffic were studied. Participants drove in a driving simulator in a total of 12 conditions; twice in each of two weather conditions and in three traffic conditions. The weather conditions were clear weather and foggy weather. The traffic conditions were without HGVs (i.e. only private cars), the current mix of HGVs and private cars, and a condition with a 70% increase of HGVs leading to an HGV column in the slow lane. The focus of the study was on assessing effects on behaviour and mental workload during filtering into traffic, and during exiting from the motorway. During the experiment driving performance was registered, behaviour was observed, self reports were collected, and the participant's heart rate was recorded. The results showed that directly after filtering into traffic the variation in driving speed increased and the minimum time headway decreased with an increase in the proportion of HGVs. Joining motorway traffic was considered to involve greater effort and risk in the condition with a column of HGVs. The effects of the conditions on heart rate are less clear, although the moment when the participants joined the traffic is clearly visible. The effects of weather conditions were limited, drivers adapting their driving behaviour in adverse weather by reducing speed. To exit the motorway is not a difficult manoeuvre. For that reason the lane change from the left hand to the fight hand lane that preceded the exit was analysed. Although increased mental effort was reported and the lane change was visible in the heart rate record, no critical changes as a result of increase in proportion of HGVs were found for this manoeuvre. However, in the condition with a column of HGVs, the exit that had to be taken was most frequently missed as HGVs obstructed the view of the exit signs. It is concluded that an increase in HGVs will make merging into traffic more mentally demanding and will decrease safety margins

Effects of listening to music, and of using a handheld and handsfree telephone on cycling behaviour

The effects of listening to music on cycling behaviour were evaluated. Twenty-five participants completed a track on a bicycle while listening to music with two standard earbuds, with one earbud, and with two in-earbuds. Conditions with high tempo music and loud volume were also included in the experiment, as were two mobile phone conditions, one in which participants operated the phone hand held and one handsfree condition. Cycle speed was not affected by listening to music, but was reduced in the telephone conditions. In general the response to auditory signals worsened when participants listened to music, in particular when listening with in-earbuds loud auditory stop signals were missed in 68% of the cases. However, when listening with only one standard earbud performance was not affected. In the conditions when participants listened to high volume and to high tempo music, the auditory stop signal was also heard in significantly fewer cases. Completing a task on the mobile phone, using both handheld and handsfree sets, resulted in increased response time to an auditory stop signal and also reduced overall auditory perception. Furthermore, handsfree operation only had minor advantages opposed to hand held operation, with only response time to an auditory stop signal resulting in faster performance. This is likely to be related to the fact that both hands could be used for braking. It is concluded that listening to music worsens auditory perception, in particular if in-earbuds are used. Furthermore, both handheld and handsfree operation of mobile phones has a negative effect on perception, potentially forming a threat to cyclist traffic safety. (C) 2011 Elsevier Ltd. All rights reserved

Improving the visibility of bicycle infrastructure

The visual characteristics of road infrastructure play a major role in a substantial number of single-bicycle crashes. The focus of this research was on finding the most common situations that result in a poorly visible bicycle infrastructure, and investigating how to improve these conditions for vulnerable cyclist populations, specifically the visually impaired and the older cyclist. Three studies were performed, a questionnaire study amongst visually impaired cyclists, focus group discussions with older cyclists, and an experiment on a closed track where participants’ vision, in particular their contrast sensitivity, was impaired. The results from the questionnaire study and the focus group discussions revealed that bollards, kerbs, and cycle path markings/shoulders are the most critical visual elements in the road infrastructure. In addition, cycling performance and cyclists’ feelings of safety worsened in conditions where the visibility of obstacles and the road’s course were the poorest. Visibility can be enhanced by placing red-white bollards, painting kerbs white, by enhancing clearness of the road’s shoulder, or by applying high contrast road markings on the side of the cycle path/road

That’s close enough:A threshold effect of time headway on the experience of risk, task diffculty, effort, and comfort

Subjective impressions of task difficulty, risk, effort, and comfort are key variables of several theories of driver behaviour. A point of difference between many of these theories is not only the importance of these variables, but also whether they are continuously present and monitored or only experienced by individuals at certain critical points in the driving task. Both a threshold relationship and evidence of constant monitoring of risk and task difficulty have been found for speed choice. In light of these conflicting findings this study seeks to examine a different part of the driving task, the choice of time headway. Participants (N = 40, aged 19 to 30) drove in a simulator behind a vehicle travelling at 50 km/h at set time headways ranging from 0.5 seconds to 4.0 seconds. After each drive ratings of task difficulty, risk, comfort, and effort were collected. In addition participants were asked to drive at the time headway they preferred. In order to assess familiarity participants also drove on both the left and right hand side of the road and the role of driving experience was also examined. The results show support for a threshold awareness of task difficulty, risk, effort, and comfort in relation to time headway. Participant's ratings of these variables tended to be low or nil at large time headways, but then around the 2.0 second mark began to noticeably increase. Feelings of task difficulty, risk, and effort were also found to be highly correlated with each other. No effect of driving experience or side of the road was found. (C) 2010 Elsevier Ltd. All rights reserved

Mobile phone use while cycling:Incidence and effects on behaviour and safety

The effects of mobile phone use on cycling behaviour were studied. In study 1, the prevalence of mobile phone use while cycling was assessed. In Groningen 2.2% of cyclists were observed talking on their phone and 0.6% were text messaging or entering a phone number. In study 2, accident-involved cyclists responded to a questionnaire. Only 0.5% stated that they were using their phone at the time of the accident. In study 3, participants used a phone while cycling. The content of the conversation was manipulated and participants also had to enter a text message. Data were compared with just cycling and cycling while listening to music. Telephoning coincided with reduced speed, reduced peripheral vision performance and increased risk and mental effort ratings. Text messaging had the largest negative impact on cycling performance. Higher mental workload and lower speed may account for the relatively low number of people calling involved in accidents. Statement of Relevance: Although perhaps mainly restricted to flat countries with a large proportion of cyclists, mobile phone use while cycling has increased and may be a threat to traffic safety, similar to phone use while driving a car. In this study, the extent of the problem was assessed by observing the proportion of cyclists using mobile phones, sending questionnaires to accident-involved cyclists and an experimental study was conducted on the effects of mobile phone use while cycling