The effects of in-car speed limiters: field studies (original) (raw)
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FIELD TRIALS WITH IN-CAR SPEED LIMITER
SUMMARY Effects of an in-car speed limiter were investigated in three European countries, the Netherlands, Spain and Sweden representing different regions and driving cultures. The study was carried out in urban and surrounding areas. Most of the European speed limit categories, ranging from 30 km/h to 120 km/h were included. The effects of the limiter were greatest in free driving conditions outside platoons. Ho w- ever, the effects of the limiter were also seen in congested traffic, even though milder than in free dri v- ing. The effects were greatest in suppressing momentary high speeds, and consequently the variation of speeds was clearly reduced by the limiter. Some negative behavioural effects were also found. These were usually slightly higher number of short time-headways and the increased frustration and stress caused by the limiter. The acceptance of the limiter increased somewhat after trying it out. However, clearly less than half of the drivers would take the limiter vo...
Improving speed behaviour: the potential of in-car speed assistance and speed limit credibility
IET Intelligent Transport Systems, 2008
Speeding is still a common practice on many roads and it contributes to a significant number of crashes. Two new approaches to solve speeding issues are focused on: intelligent speed assistance systems (ISA) and speed limit credibility. Research has indicated that ISA is promising with respect to improving speed behaviour but has not been widely implemented yet. Another promising approach to reduce speeding involves adjusting the environment to improve the speed limit credibility. The aim here is to investigate the potential of both approaches and particularly the potential of the combination of these measures. A driving simulator study was conducted to investigate the individual and combined effects of the use of an ISA system and the speed limit credibility on drivers' average speed and the amount of time spent speeding. The results indicated that both the informative ISA system used here and the speed limit credibility significantly improved speed behaviour. Drivers not using ISA appeared to be more susceptible to the speed limit credibility than those using ISA. It is concluded that both the measures can be effective to improve speed behaviour. The results obtained suggest that the properties of this particular informing and warning type of ISA could have resulted in the speed limit credibility neither affecting the amount of time speeding nor the average speed. The widespread implementation of in-car speed assistance systems, also called intelligent speed assistance (ISA), is
Impacts of Speed Limits and Information Systems on Speed Choice from a Safety Perspective
Driving a vehicle is considered a demanding task in a complex dynamic environment. For instance, driving a vehicle on urban roads, where motorized vehicles meet vulnerable road users (VRUs) creates a multifaceted environment with difficult trade-offs and interactions. Additionally, in-vehicle technology developments are being introduced to ease drivers with the driving task. However, these developments are changing "traditional" driving increasing drivers' response in terms of information processing, thus making the driving task more demanding in some respects. Therefore, the aim of the present research is to further investigate drivers' speed choice under varying traffic management regulations and in-vehicle warning systems. Paper I is based on a follow-up study conducted in order to investigate the impact on drivers' speed choice of changing the posted speed limit (PSL) in urban areas. Speed choice is crucial due to conflicts between motorized traffic and VRUs. Extensive field studies were conducted changing the PSL of 50 km/h to 40 km/h or 60 km/h. Additionally, road characteristics were taken into account, thus analyzing the impact of different traffic management regulations and geometric characteristics. The results showed a speed threshold to introduce PSLs reductions. The largest impacts of PSL changes were observed on higher road network classes and speed choice was heavily influenced by several road characteristics. Paper II investigates the free-flow speed distribution in urban areas. A probabilistic approach is presented to distinguish free-flow vehicles from constrained vehicles on urban roads. A headway range was defined where the probability for a given vehicle to be constrained was estimated. A logit model was used to estimate the regime the driver was in. The results showed a crucial headway range between 4 and 7 seconds where the probability to be constrained dropped from approximately 90 to 10 percent. Paper III describes the impact of in-vehicle technologies on speed behaviour. The COOPERS I2V Cooperative System was evaluated at the aggregate level at various levels of traffic demand and penetration of the system. A factorial experimental study was conducted with two factors and three levels. Traffic performance indicators such as speed, density, delay and travel times were considered for evaluation purposes. The results showed that driving with the system was characterized by smoother speed decelerations. Meanwhile, traffic congestion reduced the impact of the system and higher penetration levels improved the traffic operation.
Safety Science, 2016
Speeding is an important risk factor in road safety and police activities with regard to traffic (safety) are therefore to a large extent focused on tackling this problem. Within this study, researchers from Hasselt University worked together with 3 regional police units to test the effect of two frequently used speed interventions namely a speed control (i.e. stationary police control in an unmarked police car equipped with a mobile radar) with and without an advanced (digital) warning sign alongside the road. The effect of these 2 types of interventions is tested on two road segments of regional roads (with a maximum speed of 70 and 90 km/h), whereby interventions were switched between both roads during the second field experiment. To measure the effect of both methods, the average speed, 85th percentile of speed and odds of drivers exceeding the speed limit were analyzed, mainly by using general linear regression models. Results show for each tested intervention, significant speed reductions during the time that enforcement was in place. Generalizing these results, allows us to conclude that the effect during the speed control with advanced warning sign is larger compared to the speed control only (respectively À4.5 km/h and À2.5 km/h in the V85 speed) and also the continuing effect until one week after the intervention is higher. In the future, we recommend repeating the experiment on more locations, to enhance the reliability and generalizability of the results. To do so, further cooperation between knowledge institutions and field practitioners is advisable.
Impact of Active Speed Limiters on Traffic Flow and Safety: Simulation-Based Evaluation
2. Preset or dynamic limiter-set speeds. Preset systems use a fixed set speed. Dynamic systems, or intelligent speed adapters (ISAs), use real-time information to adapt the set speed to posted speed limits in various road facilities and to road and weather conditions. Although ISAs provide better control of speed, they also require communication between the vehicle and roadside beacons or the use of the Global Positioning System in order to obtain the dynamic speed limit information. These systems therefore require more expensive road infrastructure and installations in the vehicle.
EVALUATING THE BENEFITS OF ACTIVE SPEED LIMITERS AND COMPARISON TO OTHER SAFETY MEASURES
This paper evaluates the benefits of equipping European light goods vehicles (LGV) with active speed limiters and compares these benefits with those of other safety measures. In evaluating the impact of speed limiters we use a microscopic traffic simulation model which captures not only the impact of speed limiters on equipped vehicles but also the interaction between equipped and non-equipped vehicles and the resulting impact on non-equipped vehicles. The simulation results indicate that speed limiters can reduce traffic speeds by as much as 10%. Consequently, a significant reduction in the accident rate might be achieved. The safety effects and associated costs of active speed limiters are evaluated and compared to five other safety measures using a cost benefit analysis (CBA).These measures include the installation of electronic stability protection (ESP), digital tachographs, event data recorders (EDR), seat-belt reminders and seat-belt lock systems and the implementation of a professional driver training program. The CBA analysis yielded B/C ratios greater than 1 for a speed limiter set at 100 km/h, for a professional driver training programme and for devices to increase seatbelt wearing, indicating that these safety systems are economically justified for LGVs.
An investigation of characteristics associated with driving speed
1999
Previous research has shown that speed has a clear role in accident causation and injury severity. A model of speed choice, derived from the literature, is presented and explored using data collected from roadside surveys. A relationship was found between drivers' attitudes towards speeding, such as feeling comfortable at high speeds and perceived risk of detection, and their observed speed. Drivers' tolerance of illegal behaviours was also related to speed choice, where those who were tolerant of illegal behaviours drove faster than other drivers. The characteristics associated with speeding, as defined in this report, can be used to model characters in public education campaigns, such as the Transport Accident Commission advertisements, or to target specific groups of the population as the recipients of education and enforcement campaigns. This report closely follows the methodology used by Fildes, Rumbold & Leening (1991).
Improving homogeneity by dynamic speed limit systems
Accident Analysis & Prevention, 2010
Homogeneity of driving speeds is an important variable in determining road safety; more homogeneous driving speeds increase road safety. This study investigates the effect of introducing dynamic speed limit systems on homogeneity of driving speeds. A total of 46 subjects twice drove a route along 12 road sections in a driving simulator. The speed limit system (static-dynamic), the sophistication of the dynamic speed limit system (basic roadside, advanced roadside, and advanced in-car) and the situational condition (dangerous-non-dangerous) were varied. The homogeneity of driving speed, the rated credibility of the posted speed limit and the acceptance of the different dynamic speed limit systems were assessed.
IET Intelligent Transport Systems, 2011
Speeding is generally considered to be a major cause of road traffic accidents. In-car speed assistance systems aim at reducing speeding. Several trials with different types of in-car speed assistance systems, in particular intelligent speed assistance (ISA), have shown that ISA can be an effective way to reduce speeding. A basic condition for achieving significant improvements in safety involves the adaptation of ISA among vehicle drivers on a large scale. This study focuses on the issue of acceptability of ISA. It is based on a large-scale survey of 6370 individuals in Belgium (Flanders region) and 1158 persons in the Netherlands. The respondents indicated that they believed that their own driving behaviour is of great influence on accidents and traffic safety, and that contextual issues like infrastructure or other drivers are less important. Almost 95% of the respondents are in favour of ISA: seven out of ten drivers state that they want to have some informative or warning system. Three out of ten drivers even wanted to go further; they indicated a preference for a restricting type of ISA. However, drivers would only choose for more restricting systems if the penetration rates of such systems in the vehicle market were high enough.
Transportation Research Record: Journal of the Transportation Research Board, 2013
Control of traffic by a variable speed limit (VSL) has been researched for a long time, but there is a lack of consensus on its safety and operational benefits and on the impact of driver compliance. This study provides quantitative evaluations of these benefits and shows the importance of driver compliance with VSLs. VISSIM and the technique of simulated vehicle conflicts (Surrogate Safety Assessment Model) were used in the study. To validate the safety analysis, an attempt was made to correlate the simulated vehicle conflicts with historic crashes. Three scenarios of traffic conditions were considered: heavily congested, lightly congested, and uncongested. Each scenario was further examined under four driver compliance levels: low, medium, high, and very high. The results con-firmed that the VSL had safety and operational benefits for motorway traffic. The system had the highest safety benefits during highly congested traffic conditions, followed by lightly congested conditions, a...