Speed behaviour as a choice between observing and exceeding the speed limit

Despite speed behaviour being defined as a choice between several possible speeds, studies using theory of reasoned action or theory of planned behaviour to predict and understand speed behaviour have focused on exceeding and not on observing the speed limit. This study examines whether the evaluation of exceeding but also of observing the speed limit contributes to improving predictions of self-reported speed behaviour and determining intentions to produce each of these two behavioural options. For a specific driving situation (straight road with 90 km/h speed limit), 238 young male drivers reported the speed at which they would drive at and where asked to assess the theory of planned behaviour key constructs with respect to observing and exceeding the speed limit by at least 20 km/h. Results showed that the amount of explained variance of self-reported speed behaviour, as well as intentions to observe and to exceed the speed limit by at least 20 km/h, increased significantly when the evaluations of the two options were introduced in the same stepwise regression analysis. Theoretical and practical implications of the results are discussed.     

The effect of speed limit credibility on drivers' speed choice

Credibility of speed limits is a key factor affecting drivers’ compliance with speed limits. Two experiments were conducted to investigate how credibility of speed limits affects judgments of appropriate speed. The first experiment aimed to establish speeds deemed appropriate by investigating Malaysians drivers’ judgments of the appropriate speed to drive based on photographs of roads with the speed limit sign erased. Drivers chose speeds which correlated with but were higher than the actual speed limits of the roads. Analysis of road characteristics suggested they based their decisions mainly on features of the road itself rather than of the roadside. The second experiment tested the impact of credibility of speed limit information on the speed drivers judged appropriate. Drivers judged the appropriate speed to drive for the same photographs as in Experiment 1 with speed limit information provided. Four conditions were included: two conditions where the speed limit posted was 10% higher or 10% lower than the appropriate speed established in Experiment 1 (credible speed limits), and two conditions where the posted speed limit was 50% higher or 50% lower than the appropriate speed (non-credible speed limits). Posted speed limits did affect drivers’ judgments about the appropriate speed to drive. Credibility also influenced judgments whereby drivers selected appropriate speeds consistent with the speed limits for the 10% lower condition, but not for speed limits that deviated highly from the appropriate speed judged in Experiment 1.     

How choice ecology influences search in decisions from experience

Research into human decision-making has often sidestepped the question of search despite its importance across a wide range of domains such as search for food, mates, allies, visual targets or information. Recently, research on decisions from experience has made progress in finding out how individual characteristics shape search for information. Surprisingly little is known, however, about how the properties of the choice ecology shape people's search. To fill this void, we analyzed how two key ecological properties influence search effort: domain of choice (gains vs. losses) and experienced variance (variance vs. no variance). Many people search longer when facing the prospect of losses relative to gains. Moreover, most people search more in options in which they experience variance relative to options they experience as invariant. We conclude that two factors that have been identified as important determinants of choice also influence search of information.     

Stability in drivers' speed choice

Repeated speed measurements were obtained to examine drivers' consistency in speed choice. Drivers were observed at two locations along a route or for two days at the same location. Single carriageway roads were used with posted speed limits of 70 and 90 km/h. Correlation coefficients between repeated speed measures ranged from .49 to .81 for free-flowing vehicles. Higher consistency between measures was found where segments of the road were homogenous. Consistency in relation to speed limit varied as a function of roads and direction of travel. From 4% to 41% of the drivers observed legal speeds at both sites and between 43% and 100% travelled over the speed limits at both sites. The results are discussed in terms of using self-reported speed in driver surveys and modelling of driver behaviour.     

The tendency of drivers to pass other vehicles

The purpose of this study was to assess the speed differential threshold—if there is one—at which drivers decide to pass a lead vehicle. Drivers in a simulator encountered vehicles in front that were programmed to travel at speeds that were similar, slightly below, or even slightly above the drivers’ own speed. The study involved a total of 152 such passing opportunities. In almost all of the encounters with slower vehicles (traveling at speeds slower than 3 km/h of the driver) they passed them, and in two thirds of the encounters when the lead vehicles were moving at their speed they passed them too. Most surprising was that in 50% of the encounters drivers passed the lead vehicle when it was traveling faster than their average speed. In these situations drivers actually increased their own speed substantially to accomplish the passing maneuver, despite the fact that not passing the lead vehicle would not have caused any delays. The tendency to pass appears to be related to the drivers’ own speed variability: the more variable the driver’s speed the more likely he or she was to pass the vehicle ahead even when its speed was greater than their average speed. The results are interpreted in terms of (a) driver aggression, and (b) association of car following with added effort, attention overload, or risk. The latter explanation implies that the tendency to pass vehicles may be reduced with the introduction of in-vehicle technologies such as adaptive cruise control.     

Guiding drivers towards safer driving speed: Exploiting visual dominance in speed adaptation

Inappropriate speed is a main cause of accidents. Drivers are often unaware of potential risks due to inadequate speed. To prevent dangerous situations, we need to understand perceptual factors influencing human speed perception. Due to the prominent role of vision in driving, we examined the effect of visuo-spatial stimuli on speed based on the optic flow. While developing an adaptive infrastructure measure to reduce speed, we conducted two consecutive studies, a driving simulator study and a field test to investigate findings further. In both studies, we placed lights on two sides of a highway exit and either illuminated them statically or activated them in a way that they appeared to be moving towards the driver. We expected drivers to slow down more when seeing static light stimuli compared to a baseline without lights. We also expected drivers to decrease speed more in conditions with oncoming lights compared to a baseline, and to static lights, due to distorted speed perception. The first study in a static driving simulator revealed no difference between conditions. In the field test, both static lights and lights moving towards the driver led to a speed reduction compared to a baseline but did not differ from one another. Lights in general led to lower driving speed, potentially due to their warning character, but we found no difference between the light conditions, suggesting that the effect might not be based on the optic flow. Future research should investigate the relationship between driven and perceived speed more closely.     

The role of preference in speed choice

Individual differences with regard to speed preference may be a source of speed heterogeneity and conflicts in traffic, such as tailgating and dangerous overtaking. The main aim of the current study was to explore drivers’ speed preferences when driving for different reasons (saving money on fuel, driving safely, driving for fun or driving as usual) and the relationship of these preferences to observed speeds and self-reported speed. 193 drivers were interviewed at five different locations, and were asked about their speeds on roads they had just travelled. Drivers’ speeds on these roads were also sampled with a speed gun. The results showed large differences between speeds chosen for different driving purposes; the lowest speeds were chosen when the goal was economy and the highest when driving for fun. In addition, there were individual differences in speed preferences such that some drivers indicated that their usual speed was above what they believed was a safe speed while others indicated that they usually drove even slower than what they thought was safe. These differences may account for much of the speed heterogeneity observed in on-road behaviour. The results also showed that drivers’ speed choices are highly influenced by their usual speeds, even more so than their beliefs regarding what constitutes a safe speed, which may help explain non-compliance with speed limits. No relationship was found between speed choice and risk perception.     

Decision speed induces context effects in choice

The context in which a decision occurs can influence the decision-making process in many ways. In the laboratory, this is often evident in the effects of recent decisions. For instance, many experiments combine easy and difficult decisions, such as when word frequency is manipulated in lexical decision. The "blocking effect" describes how such decisions differ depending on whether the conditions are presented in pure blocks (comprised purely of easy or hard stimuli) or mixed blocks (also known as a "mixing cost"). We present a novel extension to these context effects, demonstrating in two experiments that they can be induced using conditions with identical difficulty, but different timing properties. This suggests that explanations of context effects based on task difficulty or error monitoring alone might be insufficient, and suggest a role for decision time. In prior work, we suggested such a hypothesis under the assumption that observers minimize their decision time, subject to an accuracy constraint. Consistent with this explanation, we find that decisions in slower conditions were based on less evidence when they were experienced in mixed compared to pure blocks.     

Speed of reasoning and its relation to reasoning ability

The study investigates empirical properties of reasoning speed which is conceived as the fluency of solving reasoning problems. Responses and response times in reasoning tasks are modeled jointly to clarify the covariance structure of reasoning speed and reasoning ability. To determine underlying abilities, the predictive validities of two cognitive covariates, namely perceptual and executive attention, are investigated. A sample of N = 230 test takers completed a reasoning test, Advanced Progressive Matrices (APM), and attention tests indicating perceptual and executive attention. For modeling responses the two-parameter normal ogive model, and for modeling response times the two-parameter lognormal model was applied. Results suggest that reasoning speed is a unidimensional construct representing significant individual differences, and that reasoning speed and ability are negatively correlated but clearly distinguishable constructs. Perceptual and executive attention showed differential effects on reasoning speed and reasoning ability, i.e., reasoning speed is explained by executive attention only, while reasoning ability is explained by both covariates. Implications for the assessment of reasoning are discussed.     

Evidence against a speed limit in multiple-object tracking

Everyday tasks often require us to keep track of multiple objects in dynamic scenes. Past studies show that tracking becomes more difficult as objects move faster. In the present study, we show that this trade-off may not be due to increased speed itself but may, instead, be due to the increased crowding that usually accompanies increases in speed. Here, we isolate changes in speed from variations in crowding, by projecting a tracking display either onto a small area at the center of a hemispheric projection dome or onto the entire dome. Use of the larger display increased retinal image size and object speed by a factor of 4 but did not increase interobject crowding. Results showed that tracking accuracy was equally good in the large-display condition, even when the objects traveled far into the visual periphery. Accuracy was also not reduced when we tested object speeds that limited performance in the small-display condition. These results, along with a reinterpretation of past studies, suggest that we might be able to track multiple moving objects as fast as we can a single moving object, once the effect of object crowding is eliminated.     

How to nudge drivers to reduce speed: The case of the left-digit effect

To decrease the negative consequences of a road crash, even a small reduction in driving speeds can make a significant difference. We examined the possible application of the left-digit effect as a nudge to reduce road speed. In the marketing field, this effect is based on reporting price tags that are characterized by a low leftmost number and a high rightmost number (e.g., a price tag of €14.99 rather than €15.00). We applied the same strategy to improve road safety. Participants were college students (43.75% female, mean age = 24.06 years in Study 1; 50% female, mean age = 23.53 years in Study 2) who were asked to drive in a simulator on a route that had both usual unmodified road signs (e.g., 50 km/h) and the same road signs increased or decreased by one unit (e.g., 49, 51 km/h). We compared the average median speeds in road segments with unmodified road signs with those in road segments with the corresponding modified signs. The average median speeds in the presence of a sign modified by the reduction of 1 km/h were significantly lower compared with the median average speeds recorded with unmodified signs. We showed that the application of psychological insights can reduce driving speeds and therefore increase road safety.     

Asymmetric preferences for road safety: Evidence from a stated choice experiment among car drivers

Recent research has proposed fitting responses from discrete choice experiments to asymmetric value functions consistent with prospect theory, taking into account respondents’ reference points in their valuation of choice attributes. Previous studies have mainly concentrated on travel time and cost attributes, while evidence regarding road safety attributes is very limited.This paper investigates the implicit utility of a road safety attribute, defined as the number of casualties per year in alternative car trip choices, when safety improves or deteriorates. Using appropriate statistical tests we are able to reject symmetric preferences for losses and gains in the level of safety and estimate a sigmoid value function that exhibits loss aversion and diminishing sensitivity. This adds an interesting psychological dimension to the preference of road safety. Possible implications of this finding for policy making are discussed.     

Judgments of mean speed and predictions of route choice

How are driving speeds integrated when speeds vary along a route? In a first study, we examined heuristic processes used in judgments of mean speed when the mean speeds on parts of the trip varied. The judgments deviated systematically from objective mean speeds because the distances driven at different speeds were given more weight than travel time spent on the different distances. The second study showed that when there was a 10–15 min pause during a travel the effect on the mean speed decrease was underestimated for driving speeds of 90 km/h and higher. In the third study, the objective mean speeds and the subjective biased mean speed judgments were used to predict choices between routes with different speed limits. The results showed that subjective judgments predicted decisions to maximize mean speed significantly better than objective mean speeds. Finally, some applied and basic research implications of the results were discussed.     

Development of planning and its relation to other cognitive processes

The purpose of this study was to (a) delineate the course of development of children's planning skills during school years, (b) examine whether different levels of planning exist, and (c) explore the role of other cognitive processes as cognitive correlates of planning. The participants were 250 students, 50 from each of the five targeted grades (3, 5, 7, 9, and 11). They each completed a battery of planning, attention, and simultaneous and successive processing tasks. MANOVA indicated that the main effect of grade was significant, whereas gender had no significant effect on planning. Pairwise comparisons of performance means between grades indicated that developmental trajectories were not uniform across planning tasks. Correlation and regression analyses showed that the relationship between planning tasks and attention, and simultaneous and successive processing scores varied as a function of the planning task and the grade level. Furthermore, two planning factors were found and cluster analyses of variables indicated that one of the tasks, Crack-the-Code, may represent a different kind of planning than the other planning tasks used.     

Catching ease influences perceived speed: Evidence for action-specific effects from action-based measures

According to the action-specific account of perception, people perceive the environment in terms of their ability to act. Here, we directly tested this claim by using an action-based measure of perceived speed: Participants attempted to catch a virtual fish by releasing a virtual net. The net varied in size, making the task easier or harder. We measured perceived speed by using explicit judgment-based measures and an action-based measure (time to release the net). Participants released the net later when playing with the big as compared with the small net, indicating that the fish looked to be moving more slowly when participants played with the big net. Explicit judgments of fish speed were similarly influenced by net size. These results provide converging evidence from both explicit and action-based measures that a perceiver’s ability to act influences a common underlying process, most likely perceived speed, rather than postperceptual processes such as response formation.