Towards a general theory of driver behaviour

Taylor [Taylor, D.H., 1964. Drivers' galvanic skin response and the risk of accident. Ergonomics 7, 439-451] argued that drivers attempt to maintain a constant level of anxiety when driving which Wilde [Wilde, G.J.S., 1982. The theory of risk homeostasis: implications for safety and health. Risk Anal. 2, 209-225] interpreted to be coupled to subjective estimates of the probability of collision. This theoretical paper argues that what drivers attempt to maintain is a level of task difficulty. Naatanen and Summala [Naatanen, R., Summala, H., 1976. Road User Behaviour and Traffic Accidents. North Holland/Elsevier, Amsterdam, New York] similarly rejected the concept of statistical risk as a determinant of driver behaviour, but in so doing fell back on the learning process to generate a largely automatised selection of appropriate safety margins. However it is argued here that driver behaviour cannot be acquired and executed principally in such S-R terms. The concept of task difficulty is elaborated within the framework of the task-capability interface (TCI) model, which describes the dynamic interaction between the determinants of task demand and driver capability. It is this interaction which produces different levels of task difficulty. Implications of the model are discussed regarding variation in performance, resource allocation, hierarchical decision-making and the interdependence of demand and capability. Task difficulty homeostasis is proposed as a key sub-goal in driving and speed choice is argued to be the primary solution to the problem of keeping task difficulty within selected boundaries. The relationship between task difficulty and mental workload and calibration is clarified. Evidence is cited in support of the TCI model, which clearly distinguishes task difficulty from estimates of statistical risk. However, contrary to expectation, ratings of perceived risk depart from ratings of statistical risk but track difficulty ratings almost perfectly. It now appears that feelings of risk may inform driver decision making, as Taylor originally suggested, but not in terms of risk of collision, but rather in terms of task difficulty. Finally risk homeostasis is presented as a special case of task difficulty homeostasis.     

That's close enough—A threshold effect of time headway on the experience of risk, task difficulty, 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.     

Speed maintenance under cognitive load - Implications for theories of driver behaviour

No theory of driver behaviour has yet managed to achieve widespread acceptance and use in the field of Traffic Psychology, partly due to the difficulty in testing many of the theories. However, one class of theories, the motivational theories, can be usefully split into two groups and the differences between them can then be examined. One group posits the constant monitoring and targeting of a certain subjective variable, often risk, as the controlling factor in driving. The other group however states that subjective variables such as risk are only relevant once a certain threshold has been passed.In this study we aimed to examine this difference by manipulating both speed of travel and the amount of cognitive load participants were under. Participants were asked to initially drive at their preferred speed for 1 min in a driving simulator. Participant's speed was then automatically increased or decreased by 10, 20 30 km/h or left unchanged. Participants were then required to maintain the new speed for 1 min. After this 1 min the speed was again automatically changed and had to be maintained for one more minute, but this time participants also carried out a secondary mental arithmetic task. Finally participants were asked to again drive for another 1 min at their preferred speed. This procedure was repeated seven times, once for each speed manipulation; −30, −20, −10, +0, +10, +20 and +30 km/h. After each 1 min interval verbal ratings of task difficulty, effort, feeling of risk and the typicality of the speed were collected.The results show a threshold effect in ratings of task difficulty, effort and feeling of risk, with no significant difference given between the ratings during the baseline period and the experimentally decreased speed periods until after participant's preferred speed of travel had been exceeded. Furthermore, even when under cognitive load the threshold relationship was still apparent, if diminished. Finally it appears that when under cognitive load drivers have difficulty maintaining a travelling speed which is lower than the speed at which they would prefer to drive. However, driving at a speed in excess of their preferred speed appears to be easier to maintain, at least in the short term.     

Effects of measurement assumptions on estimations of risk of collision

This paper provides a replication and extension of previous research describing the relationship between risk of fatal collision and driver blood alcohol content. Risk of collision indices are derived through a comparison of the blood alcohol levels of nighttime Canadian drivers and nighttime driver fatalities. In the context of these data sets an assessment is made of the effects of different treatments of missing data upon estimations of risk of collision. Assumptions regarding the distribution of alcohol among non-respondents in roadside surveys, as well as among driver fatalities who are not tested for alcohol, are shown to have substantial implications for the magnitude of the risk factors derived. Nevertheless, although the magnitude of the relationship between driver blood alcohol and risk of fatal collision varies as a function of the assumptions utilized, the directionality of the relationship corresponds consistently to the results reported in previous investigations.     

Safety impacts due to the incompatibility of SUVs, minivans, and pickup trucks in two-vehicle collisions

This research sets out to estimate the effects of vehicle incompatibility on the risk of death or major injury to drivers involved in two-vehicle collisions.Based on data for 2,999,395 drivers, logistic regression was used to model the risk of driver death or major injury (defined has being hospitalized). Our analyses show that pickup trucks, minivans and sport utility vehicles (SUVs) are more aggressive than cars for the driver of the other vehicle and more protective for their own drivers. The effect of the pickups is more pronounced in terms of aggressivity. The point estimates are comparable to those in the Toy and Hammitt study [Toy, E.L., Hammitt, J.K., 2003. Safety impacts of SUVs, minivans, and pickup trucks in two-vehicle crashes. Risk Analysis 23, 641–650], but, in contrast to that study, we are now able to establish that a greater number of these effects are statistically significant with a larger sample size.Like vehicle mass and type, other characteristics of drivers and the circumstances of the collision influence the driver’s condition after impact. Male drivers, older drivers, drivers who are not wearing safety belts, collisions occurring in a higher speed zone and head-on collisions significantly increase the risk of death. Except for the driver’s sex, all of these categories are also associated with an increased risk of death or of being hospitalized after being involved in a two-vehicle collision. For this risk, a significant increase is associated with female drivers.     

Explicit and implicit self-enhancement biases in drivers and their relationship to driving violations and crash-risk optimism

Previous research has found that drivers tend to consider themselves superior to their peers on both driving ability and driving caution, as well as judging themselves as at less risk of a crash (crash-risk optimism). These studies have relied on explicit measures by getting drivers to respond to written items. The current study measured 158 New Zealand drivers’ explicit and implicit attitudes towards their own driving attributes in comparison with others. Implicit attitudes were measured using a computer-based reaction time task, the Implicit Association Test (IAT). Both explicit and implicit self-enhancement biases were found in driver ability and driver caution. Implicit biases were considerably stronger than explicit biases and men demonstrated stronger self-enhancement biases in driving ability than women. Explicit and implicit ratings of driving ability and explicit ratings of driver caution predicted crash-risk optimism. Explicit and implicit ratings of driving caution predicted a measure of driving violations. The implications for safety interventions and research on drivers’ mental processes are discussed particularly in regard to the ability of implicit measures to bypass social desirability effects.     

Exploring the effects of driving experience on hazard awareness and risk perception via real-time hazard identification,hazard classification,and rating tasks

This study investigated the effects of driving experience on hazard awareness and risk perception skills. These topics have previously been investigated separately, yet a novel approach is suggested where hazard awareness and risk perception are examined concurrently. Young, newly qualified drivers, experienced drivers, and a group of commercial drivers, namely, taxi drivers performed three consecutive tasks: (1) observed 10 short movies of real-world driving situations and were asked to press a button each time they identified a hazardous situation; (2) observed one of three possible sub-sets of 8 movies (out of the 10 they have seen earlier) for the second time, and were asked to categorize them into an arbitrary number of clusters according to the similarity in their hazardous situation; and (3) observed the same sub-set for a third time and following each movie were asked to rate its level of hazardousness. The first task is considered a real-time identification task while the other two are performed using hindsight. During it participants’ eye movements were recorded. Results showed that taxi drivers were more sensitive to hidden hazards than the other driver groups and that young-novices were the least sensitive. Young-novice drivers also relied heavily on materialized hazards in their categorization structure. In addition, it emerged that risk perception was derived from two major components: the likelihood of a crash and the severity of its outcome. Yet, the outcome was rarely considered under time pressure (i.e., in real-time hazard identification tasks). Using hindsight, when drivers were provided with the opportunity to rate the movies’ hazardousness more freely (rating task) they considered both components. Otherwise, in the categorization task, they usually chose the severity of the crash outcome as their dominant criterion. Theoretical and practical implications are discussed.     

Cross-cultural differences in driver risk-perception

This study investigated differences in risk-perception among U.S., Spanish, West German, and Brazilian drivers. Subjects estimated the risk involved in slide-projected traffic scenes. The scenes, photographed in the United States and Spain, were rated for the amount of risk by using a seven-point scale. The subject groups in each country included younger, middle-aged, and older nonprofessional drivers, as well as middle-aged professional (bus, taxi, or truck) drivers. In the data analyses, the independent variables were subjects' country, age, professional driving experience, and sex, and 23 dichotomously coded characteristics of the traffic scenes. The following are the main findings: (1) Spanish drivers reported the highest risk, while U.S. drivers reported the lowest risk; (2) younger drivers tended to report lower risk than middle-aged and older drivers; (3) nineteen of the 23 analysed characteristics of traffic scenes contributed significantly to risk ratings, even after simultaneously controlling for the effects of all other scene characteristics; (4) ten scene characteristics had a differential effect on the risk ratings in the four tested countries; (5) two scene characteristics had a differential effect on the risk ratings in the four tested subject groups; (6) none of the variables affected differentially the risk ratings of professional vs. nonprofessional drivers and males vs. females. These findings provide information concerning the desirable country- and age-specific emphasis in driver education, driver licensing, and public information campaigns.     

The influence of passengers on the risk of the driver causing a car collision in Spain. Analysis of collisions from 1990 to 1999

Objective: To determine how the number of passengers, their age and their sex influence the risk of different types of Spanish drivers causing a collision between two or more cars.Methods: We selected, from the Spanish database of traffic crashes resulting in personal injuries or death, those collisions between two or more cars that occurred between 1990 and 1999 in which only one of the involved drivers committed a driving infraction. These drivers were considered the cases; non-infractor drivers were considered their matched controls. We collected information on the number, age and sex of the passengers in each vehicle, along with some potential confounding variables of the drivers and the vehicles involved. Crude and adjusted odds ratios were calculated for the main categories of driver and passenger.Results: A protective effect for the presence of passengers was detected (adjusted odds ratio: 0.69; 95% CI: 0.67-0.70). The protective effect was higher for drivers aged more than 45 years and lower for the youngest drivers (<24 years old). The strongest association was observed for female passengers who accompanied male drivers. The protective effect was lower for passengers older than 64 years.Conclusion: Our results suggest that drivers are less likely to cause a car collision between two or more cars that results in personal injuries or death when they are accompanied by passengers, regardless of driver or passenger characteristics.     

Voluntary risk taking and skill deficits in young driver accidents in the UK

In absolute terms, young drivers have three to four times as many accidents per year as older drivers; and even allowing for their relative numbers in the population, their accident involvement is about 2.5 times higher than older drivers. A sample of 3437 accident reports was considered, including 1296 in detail, from midland police forces in the UK, involving drivers aged 17-25, and covering the years 1994-1996 inclusive. Four types of accident were identified as being of particular concern due to their high frequency: 'cross-flow'-turns; rear-end shunts; loss of control on bends; and accidents in darkness. (The term 'cross-flow' is used in relation to turns to denote an intersection accident where a driver is turning across the path of oncoming traffic, i.e., left turns in the US and continental Europe, but right turns in the UK and other countries where driving on the left side of the road is the norm.) An examination of driver risk taking behaviours as revealed in police interviews gave an insight into some of the motivational factors underlying young driver behaviour. Young driver accidents of all types are found to be frequently the result of 'risk taking' factors as opposed to 'skill deficit' factors. It had previously been thought that one of the main problems that young drivers have is in the area of specific skills needed in the driving task. However, it appears that a large percentage of their accidents are purely the result of two or three failures resulting from voluntary risk taking behaviour, rather than skill deficits per se. It is shown that specific groups of young drivers can even be considered as above average in driving skills, but simultaneously have a higher accident involvement due to their voluntary decisions to take risks.     

Age and sex differences in the risk of causing vehicle collisions in Spain, 1990 to 1999

This retrospective, paired case-control study was designed to estimate crude and adjusted effects of age and sex on the risk of causing collisions between vehicles with four or more wheels in Spain during the period from 1990 to 1999. We selected all 220284 collisions registered from 1990 to 1999 in the Spanish Dirección General de Tráfico (DGT) traffic crash database in which only one driver committed any infraction. Information was collected about age, sex and several confounding factors for both the responsible and paired-by-collision nonresponsible drivers. Crude and adjusted odds ratios (aORs) were calculated for each age and sex category. For men, the lowest risk was seen for drivers aged 25-49 years. Below the age of 35 years the crude odds ratio (cOR) was highest in the 18-24-year-old group (1.61; CI: 1.57-1.65). The risk increased significantly and exponentially after the age of 50 years, to a maximum odds ratio of 3.71 (3.43-4.00) for drivers aged >74 years. In women, the lowest risk values were found for the 25-44-year-old age group. In older women the risk increased significantly with age to a maximum odds ratio of 3.02 (2.31-3.97) in the oldest age group. aOR estimates tended to be lower than crude estimates for drivers younger than 40 years of age, but the opposite was seen for drivers 40 years old and older. Regarding sex differences, among younger drivers crude and aORs for men were higher than for women. Our results suggest that the risk of causing a collision between vehicles with four or more wheels is directly dependent on the driver's age.     

Associations between age,gender, psychosocial and health characteristics in the Candrive II study cohort

The relations among driving-related psychosocial measures (e.g., driving comfort, attitudes toward driving) and measures of self-reported health were examined in the context of driver characteristics (i.e., age and gender) within the Canadian Driving Research Initiative for Vehicular Safety in the Elderly (Candrive II) baseline data, available for the cohort of 928 drivers, 70 years of age and older. Older members of the cohort had lower comfort scores and poorer perceptions of their driving abilities. Men reported significantly higher levels of driving comfort than women. When analyses including health were controlled for age and gender, significant relations with health status were evident for most of the psychosocial measures. These findings extend previous research and suggest that attitudes, beliefs, and perceptions about driving may be influenced by health status and act as mediators in the self-regulation process.     

An examination of the environmental,driver and vehicle factors associated with the serious and fatal crashes of older rural drivers

Motor vehicle crashes involving rural drivers aged 75 years and over are more than twice as likely to result in a serious or fatal injury as those involving their urban counterparts. The current study examined some of the reasons for this using a database of police-reported crashes (2004–2008) to identify the environmental (lighting, road and weather conditions, road layout, road surface, speed limit), driver (driver error, crash type), and vehicle (vehicle age) factors that are associated with the crashes of older rural drivers. It also determined whether these same factors are associated with an increased likelihood of serious or fatal injury in younger drivers for whom frailty does not contribute to the resulting injury severity. A number of environmental (i.e., undivided, unsealed, curved and inclined roads, and areas with a speed limit of 100 km/h or greater) and driver (i.e., collision with a fixed object and rolling over) factors were more frequent in the crashes of older rural drivers and additionally associated with increased injury severity in younger drivers. Moreover, when these environmental factors were entered into a logistic regression model to predict whether older drivers who were involved in crashes did or did not sustain a serious or fatal injury, it was found that each factor independently increased the likelihood of a serious or fatal injury. Changes, such as the provision of divided and sealed roads, greater protection from fixed roadside objects, and reduced speed limits, appear to be indicated in order to improve the safety of the rural driving environment for drivers of all ages. Additionally, older rural drivers should be encouraged to reduce their exposure to these risky circumstances.     

Are rural older drivers subject to low-mileage bias?

Comparing exposure-based collision statistics between older drivers based on age alone erroneously assumes a linear relationship between exposure and collision frequency. Research has suggested that low-mileage drivers, of any age, tend to have higher exposure-based collision rates because the majority of their travel is typically on congested city streets with higher potential for collisions, referred to as “low-mileage bias”. It is unclear whether it is appropriate to extend this perspective to rural older drivers, where it could be expected they would likely have very different travel habits than an urban older driver with equivalent annual mileage. Consequently, reliance on “low-mileage-bias” as an explanation for high collision rates among seniors would benefit from the distinction of the differences in the type of driving exposure between urban and rural drivers.This paper used the detailed driving exposure information obtained from a Global Positioning System (GPS) supported travel diary study to explore whether “low-mileage bias” exists for rural older drivers. Revealed behaviour from GPS travel diaries of a convenience sample of 60 rural drivers aged 54–92 years showed the proportion of travel on urban streets increased with self-reported mileage and decreased with age. This finding is contrary to previous results where no distinction was made between urban and rural drivers. These results, combined with previous research showing the oldest rural drivers (81 years and older) have higher collision rates than their urban counterparts, suggests “low-mileage bias” may not exist in the rural context. It is possible the collision risk for the oldest rural drivers is understated, but further research is required. Self-reported mileage groups are a useful way to organize and analyze exposure and collision information, but age group analysis should not be excluded.     

The effects of on-street parking and road environment visual complexity on travel speed and reaction time

On-street parking is associated with elevated crash risk. It is not known how drivers’ mental workload and behaviour in the presence of on-street parking contributes to, or fails to reduce, this increased crash risk. On-street parking tends to co-exist with visually complex streetscapes that may affect workload and crash risk in their own right. The present paper reports results from a driving simulator study examining the effects of on-street parking and road environment visual complexity on driver behaviour and surrogate measures of crash risk. Twenty-nine participants drove a simulated urban commercial and arterial route. Compared to sections with no parking bays or empty parking bays, in the presence of occupied parking bays drivers lowered their speed and shifted their lateral position towards roadway centre to compensate for the higher mental workload they reported experiencing. However, this compensation was not sufficient to reduce drivers’ reaction time on a safety-relevant peripheral detection task or to an unexpected pedestrian hazard. Compared to the urban road environments, the less visually complex arterial road environment was associated with speeds that were closer to the posted limit, lower speed variability and lower workload ratings. These results support theoretical positions that proffer workload as a mediating variable of speed choice. However, drivers in this study did not modify their speed sufficiently to maintain safe hazard response times in complex environments with on-street parking. This inadequate speed compensation is likely to affect real world crash risk.     

A rear-end collision risk assessment model based on drivers’ collision avoidance process under influences of cell phone use and gender—A driving simulator based study

Driver’s collision avoidance performance has a direct link to the collision risk and crash severity. Previous studies demonstrated that the distracted driving, such as using a cell phone while driving, disrupted the driver’s performance on road. This study aimed to investigate the manner and extent to which cell phone use and driver’s gender affected driving performance and collision risk in a rear-end collision avoidance process. Forty-two licensed drivers completed the driving simulation experiment in three phone use conditions: no phone use, hands-free, and hand-held, in which the drivers drove in a car-following situation with potential rear-end collision risks caused by the leading vehicle’s sudden deceleration. Based on the experiment data, a rear-end collision risk assessment model was developed to assess the influence of cell phone use and driver’s gender. The cell phone use and driver’s gender were found to be significant factors that affected the braking performances in the rear-end collision avoidance process, including the brake reaction time, the deceleration adjusting time and the maximum deceleration rate. The minimum headway distance between the leading vehicle and the simulator during the rear-end collision avoidance process was the final output variable, which could be used to measure the rear-end collision risk and judge whether a collision occurred. The results showed that although cell phone use drivers took some compensatory behaviors in the collision avoidance process to reduce the mental workload, the collision risk in cell phone use conditions was still higher than that without the phone use. More importantly, the results proved that the hands-free condition did not eliminate the safety problem associated with distracted driving because it impaired the driving performance in the same way as much as the use of hand-held phones. In addition, the gender effect indicated that although female drivers had longer reaction time than male drivers in critical situation, they were more quickly in braking with larger maximum deceleration rate, and they tended to keep a larger safety margin with the leading vehicle compared to male drivers. The findings shed some light on the further development of advanced collision avoidance technologies and the targeted intervention strategies about cell phone use while driving.     

The prevalence of, and factors associated with, serious crashes involving a distracting activity

The study's objectives were to determine the prevalence and types of distracting activities involved in serious crashes, and to explore the factors associated with such crashes. We interviewed 1367 drivers who attended hospital in Perth, Western Australia between April 2002 and July 2004 following a crash. A structured questionnaire was administered to each driver and supplementary data were collected from ambulance and medical records. Over 30% of drivers (433, 31.7%) cited at least one distracting activity at the time of crashing and driver distraction was reported to have contributed to 13.6% of all crashes. The major distracting activities were conversing with passengers (155, 11.3%), lack of concentration (148, 10.8%) and outside factors (121, 8.9%). Using logistic regression, a distracting activity at the time of a crash was significantly more likely among drivers with shorter driving experience (0-9 years, 38.3% versus >or=30 years, 21.0%, p<0.001). Distracting activities at the time of serious crashes are common and can cause crashes, and the types of activities reported are varied. Increased driver awareness of the adverse consequences of distracted driving with a focus on novice drivers, enforcement of existing laws (e.g. those requiring a driver to maintain proper control of a vehicle), and progress on engineering initiatives (such as collision warning systems) are needed to reduce injury.     

Driving performance during concurrent cell-phone use: are drivers aware of their performance decrements?

Prior research has documented the manner in which a variety of driving performance measures are impacted by concurrent cell-phone use as well as the influence of age and gender of the driver. This current study examined the extent to which different driver groups are aware of their associated performance decrements. Subjects' confidence in dealing with distractors while driving and their ratings of task performance and demand were compared with their actual driving performance in the presence of a cell-phone task. While high confidence ratings appeared to be predictive of better driving performance for male drivers (as confidence increased, the size of the distraction effects decreased), this relationship did not hold for females; in fact, for older females, as confidence increased, performance decreased. Additionally, when drivers were matched in terms of confidence level, brake responses of older females were slowed to a much greater extent (0.38 s) than were brake responses of any other group (0.10s for younger males and females and 0.07 s for older males). Finally, females also rated the driving task as less demanding than males, even though their performance was more greatly affected by distraction. These results suggest that many drivers may not be aware of their decreased performance while using cell-phones and that it may be particularly important to target educational campaigns on driver distraction towards female drivers for whom there tended to be a greater discrepancy between driver perceptions and actual performance.     

Young drivers' optimism bias for accident risk and driving skill: Accountability and insight experience manipulations

This study aimed to determine whether two brief, low cost interventions would reduce young drivers’ optimism bias for their driving skills and accident risk perceptions. This tendency for such drivers to perceive themselves as more skilful and less prone to driving accidents than their peers may lead to less engagement in precautionary driving behaviours and a greater engagement in more dangerous driving behaviour. 243 young drivers (aged 17–25 years) were randomly allocated to one of three groups: accountability, insight or control. All participants provided both overall and specific situation ratings of their driving skills and accident risk relative to a typical young driver. Prior to completing the questionnaire, those in the accountability condition were first advised that their driving skills and accident risk would be later assessed via a driving simulator. Those in the insight condition first underwent a difficult computer-based hazard perception task designed to provide participants with insight into their potential limitations when responding to hazards in difficult and unpredictable driving situations. Participants in the control condition completed only the questionnaire. Results showed that the accountability manipulation was effective in reducing optimism bias in terms of participants’ comparative ratings of their accident risk in specific situations, though only for less experienced drivers. In contrast, among more experienced males, participants in the insight condition showed greater optimism bias for overall accident risk than their counterparts in the accountability or control groups. There were no effects of the manipulations on drivers’ skills ratings. The differential effects of the two types of manipulations on optimism bias relating to one's accident risk in different subgroups of the young driver sample highlight the importance of targeting interventions for different levels of experience. Accountability interventions may be beneficial for less experienced young drivers but the results suggest exercising caution with the use of insight type interventions, particularly hazard perception style tasks, for more experienced young drivers typically still in the provisional stage of graduated licensing systems.     

Late detection of hazards in traffic: A matter of response bias?

In this study, results from two different hazard perception tests are presented: the first one is a classic hazard-perception test in which participants must respond – while watching real traffic video scenes – by pressing the space bar in a keyboard when they think there is a collision risk between the camera car and the vehicle ahead. In the second task we use fragments of the same scenes but in this case they are adapted to a signal detection task – a ‘yes’/‘no’ task. Here, participants – most of them, University students – must respond, when the fragment of the video scene ends, whether they think the collision risk had started yet or not. While in the first task we have a latency measure (the time necessary for the driver to respond to a hazard), in the second task we obtain two separate measures of sensitivity and criterion. Sensitivity is the driver’s ability to discriminate in a proper way the presence vs. absence of the signal (hazard) while the criterion is the response bias a driver sets to consider that there is a hazard or not. His/her criterion could be more conservative – the participant demands many cues to respond that the signal is present, neutral or even liberal – the participant will respond that the signal is present with very few cues. The aim of the study is to find out if our latency measure is associated with a different sensitivity and/or criterion. The results of the present study show that drivers who had greater latencies and drivers who had very low latencies yield a very similar sensitivity mean value. Nevertheless, there was a significant difference between these two groups of drivers in criterion: those drivers who had greater latencies in the first task were also more conservative in the second task. That is, the latter responded less frequently that there was danger in the sequences. We interpret that greater latencies in our first hazard perception test could be due to a stricter or more conservative criterion, rather than a low sensitivity to perceptual information for collision risk. Drivers with a more conservative criterion need more evidences of danger, thus taking longer to respond.