Pirkko Rämä

EFFECTS OF WEATHER-CONTROLLED VARIABLE SPEED LIMITS AND WARNING SIGNS ON DRIVER BEHAVIOR

This study was designed to investigate the effects of weather-controlled speed limits and signs for slippery road conditions on driver behavior on the Finnish E18 test site. Local weather and road conditions were monitored from two unmanned road weather stations. The speed limits were lowered automatically during adverse road conditions, and in some cases signs for slippery road conditions were displayed as well. Speed and headway data were obtained from loop detectors. The results showed that in winter the change of the posted speed limit from 100 km/h to 80 km/h decreased the mean speed of cars traveling in free-flow traffic by 3.4 km/h, in addition to the average mean speed reduction of 6.3 km/h caused by adverse weather and road surface conditions. When poor road conditions were difficult to detect (e.g., there was no rain or snowfall or the rain was insignificant), the effect was 1.9 km/h higher (i.e., the reduction was 5.3 km/h). When road conditions were such that signs for slippery road conditions were also displayed, the variable speed limit system reduced the mean speed by 1.8 km/h, whereas the reduction caused by the weather was 9.3 km/h. In addition to the effects on mean speed, lowering of the speed limit decreased the speed variance. There was no remarkable effect on headways. The signs decreased speeds also on the road section next to the equipped section. The main implication of the study is that the system improved traffic safety by decreasing mean speeds and speed deviation.

Effects of variable message signs for slippery road conditions on driving speed and headways

Abstract This field study investigated the effects of two variable message signs (VMS) on driver behaviour. Specifically, the signs were a warning sign for slippery road conditions and a minimum headway sign. The study was performed as a before-and-after experiment at three test sites in Finland with an after period covering two winter seasons. The results showed that the slippery road condition sign reduced the mean speed on slippery roads by 1–2 km/h in addition to the decrease caused by the adverse road conditions. The minimum headway sign decreased the proportion of headways shorter than 1.5 s for cars in car-following situations, in addition to a speed reduction of 1 km/h. The effects were somewhat smaller during the second winter than the first.

Effects of variable message signs for slippery road conditions on reported driver behaviour

A field study by Rama and Kulmala (Rama, P., Kulmala, R. (2000). Effects of variable message signs for slippery road conditions on driving speed and headways. Transportation Research, Part F, 3, 85–94.) showed that a variable message sign warning about slippery road conditions reduced the mean speed by 1–2 km/h. The study also showed that a variable message sign recommending a minimum headway between vehicles decreased the proportion of short headways. However, the signs may have other effects on driver behaviour besides those measurable in terms of speed and headway, and this study was designed to investigate such potential effects. In total, 114 drivers who had encountered the slippery road condition sign and 111 drivers who had encountered the sign showing recommended minimum headway in adverse road surface conditions were interviewed. The results suggested that these variable message signs do indeed have other effects, such as the refocusing of attention to seek cues on potential hazards, testing the slipperiness of the road, and more careful passing behaviour. On the other hand, the results suggested that driving speed and headway are essential variables with which many other variables correlate.

Driver Acceptance of Weather-Controlled Road Signs and Displays

This study was designed to investigate driver acceptance of the weather-controlled road signs and displays on Finland’s southern coast where road condition changes are particularly frequent and rapid. There were 36 variable speed limit signs and five variable message displays to warn about hazardous conditions on the 14-km-long experimental road section. Local weather and road surface conditions were monitored automatically from road weather stations; the information gathered was used for determining appropriate speed limit, as well as for controlling variable slippery road signs and temperature displays. Five hundred ninety drivers were interviewed 3, 4, 11, and 13 months after the introduction of this new road section. The results showed that drivers recalled the variable signs very well. Furthermore, 81 percent of the drivers said that the posted speed limit was appropriate, and 95 percent of the drivers stated that the variable speed limits were useful. However, only a relatively small proportion of drivers estimated that the slippery road sign or temperature display influenced their behavior. The main implication of this study is that the concept of the weather-controlled road signs and displays is a promising one. However, objective data will be collected in order to estimate the effects of the weather-controlled road signs and displays on driver behavior and to evaluate the profitability of the system.

Visual demand of bilingual message signs displaying alternating text messages

This field study was designed to compare the visual demand of variable message signs (VMSs). Specifically, three VMS types were evaluated: a sign displaying a message alternately in Finnish and Swedish (2.0 s in each language), a sign displaying the same messages simultaneously, and a sign displaying air and road surface temperatures in Finnish. The data were collected by recording the eye movements of 38 drivers during highway driving. The main results suggested that the sign displaying alternating bilingual messages was no more demanding than the VMS displaying the same messages simultaneously. However, this conclusion is limited to those specific signs and conditions, and more research is needed for related applications in various conditions. The results further suggested that VMSs involving effective technologies might be rather demanding in comparison to the fixed signs.

Can cyclist safety be improved with intelligent transport systems

In recent years, Intelligent Transport Systems (ITS) have assisted in the decrease of road traffic fatalities, particularly amongst passenger car occupants. Vulnerable Road Users (VRUs) such as pedestrians, cyclists, moped riders and motorcyclists, however, have not been that much in focus when developing ITS. Therefore, there is a clear need for ITS which specifically address VRUs as an integrated element of the traffic system. This paper presents the results of a quantitative safety impact assessment of five systems that were estimated to have high potential to improve the safety of cyclists, namely: Blind Spot Detection (BSD), Bicycle to Vehicle communication (B2V), Intersection safety (INS), Pedestrian and Cyclist Detection System+Emergency Braking (PCDS+EBR) and VRU Beacon System (VBS). An ex-ante assessment method proposed by Kulmala (2010) targeted to assess the effects of ITS for cars was applied and further developed in this study to assess the safety impacts of ITS specifically designed for VRUs. The main results of the assessment showed that all investigated systems affect cyclist safety in a positive way by preventing fatalities and injuries. The estimates considering 2012 accident data and full penetration showed that the highest effects could be obtained by the implementation of PCDS+EBR and B2V, whereas VBS had the lowest effect. The estimated yearly reduction in cyclist fatalities in the EU-28 varied between 77 and 286 per system. A forecast for 2030, taking into accounts the estimated accident trends and penetration rates, showed the highest effects for PCDS+EBR and BSD.

Three Driver and Operator Behaviour Models in the Context of Automated Driving – Identification of Issues from Human Actor Perspective

The study aimed to systematically define human issues related to automated driving. Three theoretical approaches were applied into two automation scenarios, low and high, in urban and motorway driving. The analysis encompasses five use cases in both environments, and several contextual circumstances. The list of approximately 13 human issues was provided. All theoretical approaches showed to be useful in defining the issues, and the views complemented each other. The core task analysis, not previously showed to be promising model for analyzing automated driving, and should be further developed. The other approaches applied were the traditional driver behavior theories called as motivational theories and the model for human actor operator as information processor.

396 Acceptance and impacts of a real time reindeer warning service

Background About 4000 reindeer die each year in traffic, causing significant costs. This study investigated the acceptability of a real-time reindeer warning service and its potential impacts on driver behaviour, foresight and traffic safety. Methods Professional heavy goods vehicle drivers participating in the field test on two main roads in Northern Finland received real time warnings based on sightings of reindeer on or near the road. The information was provided by the same group of drivers and a group of reindeer herders. The warning system was a simple smart phone application and was designed to be easy to use. When a driver saw reindeer near the road, he touched a circle on the screen of a smart phone installed in their vehicle, sending the warning to all nearby drivers using the application. The warnings were in effect within an area of radius 500 m from the initial warning for the following 2–4 hours. Results The impacts of the service were evaluated by driver questionnaires and interviews. The drivers were interviewed twice, after about 6 and 12 months use of the service. 23 drivers participated in the interviews. In addition, also driving companies, reindeer herders and other stakeholders and experts were interviewed. The majority of drivers assessed the service useful. They especially liked the possibility to foresee unexpected situations. Drivers valued service simplicity. It was estimated that, if installed in every vehicle, the service could lead to a decrease in reindeer accidents by 9.7–17.8%, corresponding to a reduction of 395–725 accidents annually. Regarding all injury accidents in the area, the service was estimated to cause a reduction of 0.76–1.52% corresponding to 2–4 injury accidents annually. Conclusions The service worked well and was well received by its users. The results of the trial were promising.