Effects of Engaging in Passenger Conversations on Distraction While Driving

Hailey Hrvatin (Second and Third Year Category)

Expanding the Research on Safe Injection Sites and Harm Reduction Services


Distracted driving is a major issue which results in many crashes leading to fatalities and devastating injuries in drivers and passengers. Conversations with passengers have the potential to distract drivers from the primary task of ensuring safe vehicle operation which could therefore negatively impact the performance of the driver. This research study aims to determine whether participating in conversation with passengers is more distracting than having passengers present without talking to them, even if they are talking amongst themselves. Drivers with a valid Class-5 British Columbia licence will make up the participants of this study and must have 10 or more years of driving experience to be included. Participants will partake in three separate driving simulation sessions under each of the conditions of talking to passengers (talking condition), hearing passengers talking amongst themselves but not joining the conversation (listening condition), and having silent passengers in the car (control condition). The simulation performance will be scored based on hazard avoidance and smoothness of steering. This study will allow researchers to determine whether there is a causal relationship between different levels of driver-passenger interaction and increase awareness of what types of interactions have the most potential for negatively impacting driving performance.

          Each year in Canada, unsafe driving results in thousands of motor vehicle accidents. In 2019, there were 1,762 deaths that occurred in Canada due to motor vehicle accidents (Transportation Canada, 2019). In addition to these fatal motor vehicle accidents, there were 8,917 serious hospitalized injury cases reported in 2019 that occurred as a result of driving accidents (Transportation Canada, 2019). Given the magnitude of the fatalities and injuries caused by motor vehicle accidents, it is not surprising that multitudes of applied research projects focus on ways to improve driver safety and reduce crash frequencies. Distracted driving is a leading causal and contributing factor in fatal and injury-causing vehicular accidents; of the fatal car crashes reported in Canada during 2019, 21.7% were determined to have had driver distraction as a factor in the accident (Transportation Canada, 2021).

          Despite every Canadian province having some form of legislation around distracted driving (Distracted Driving Laws in Canada, 2021), driver distractions continue to be difficult to control and understand. One of the reasons for secondary tasks causing distraction while driving is because such tasks take up a portion of the brain’s working memory capacity, splitting it between tasks and decreasing processing capacity for the primary task of driving and responding to road-related stimuli (Walker, Eng, & Trick, 2021). Laws and research in distracted driving have largely focused on the impact of cellular devices as distractions for motor vehicle operators. Multiple studies have indicated that cell phone usage while driving has negative impacts one drivers’ ability to operate the vehicle in a safe and attentive manner. One study in found that processing and replying to verbal messages over the phone significantly decreased drivers’ perception of safe road spacing and saw great indecisiveness in distracted drivers (Cooper & Zheng, 2002). Other research has indicated that tasks involving physically touching a cellular device while driving, such as texting or phone calls that are not hands free, have a greater negative impact on driving performance than hands-free calling ( Shaaban, Gaweesh, & Ahmed, 2020), and that technological distractions impact multiple aspects of driving such as speed variability and lane-change safety, (Crisler et al., 2008). Studies have also suggested that combining sleep-deprivation with distractions can increase the magnitude of the impact of the distractions (Matthews, Kontou, Naweed, Sargent, & Roach, 2018), and that engaging in distracting actions can have effects that persist for over 10 seconds while driving (Bock, Stojan, Wechsler, Mack, & Voelcker-Rehage, 2021).

          Although cell phones and technology have been the initial and most prominent focuses in distracted driving research, presence of and interaction with passengers is also being explored as a potential distracting factor for motor vehicle operators. Given that research has shown conversation to limit the functional field of view (Atchley & Dressel, 2004), as well as splitting working memory capacity (Walker et al., 2021), it is logical to assess that in car conversations could have similar impacts to those occurring over the phone. Gugerty, Rakauskas, and Brooks conducted a study comparing remote hands-free conversations and conversations with passenger in the vehicle. Their findings suggested that engaging in conversations with passengers was a distraction and negatively impacted driving performance; however hands-free phone conversations were still found to be a significantly greater distraction (2004). Their findings have been consistently replicated in similar studies such as Drews, Pasupathi, and Stayer in 2008, and Amado and Ulupına in 2005.

          Within the topic of passenger impact on driver distraction and performance, there have not been any studies comparing the impacts of different ways of interacting with passengers in the vehicle. A study by Zhang, Mehotra, and Roberts indicated that the mere presence of a passenger is not negative and can actually improve driving performance depending on the types of interactions occurring (2019). Charlton and Starkey found in their research that the specific actions that a passenger engages can have an impact on drivers’ ability to focus and drive safely, but that this impact could be positive or negative depending on if the behaviour of the passenger was one of assistance or distraction, with conversation being on of the potential distractors (2020). This study, while useful in informing the types of passenger behaviours that are potentially helpful or harmful to a driver’s performance, it was not a true experiment, therefore it could not establish a relationship between the way a driver interacts with their passengers and their ability to focus and drive safely. This research study will aim to determine whether engaging in conversation with in-car passengers is distracting factor that impacts driving performance, as compared to having passenger presence without noise, or having passengers talking to one another without the driver joining the conversation. The researchers hypothesize that engaging in conversation will be more distracting and therefore have greater negative impact on driving performance than having passengers talking in the background or staying silent. The null hypothesis would be if there is no relationship between the level of conversational interaction with passengers and driving performance. Engaging in conversation will be defined as speaking to and responding to questions asked by the passengers. Passengers are defined as individuals who are present in the vehicle but are not currently responsible for its operation. Passengers talking in the background will mean that there is a conversation happening in the car, but the driver will not be involved in speaking or responding. Driving performance will be the measure of how well one recognizes and avoids hazards and maintains lane positioning during a driving simulation test.


          This research study will use 60-90 volunteer participants. Participants would be recruited through an online advertisement and intake screening questionnaire. The intake questionnaire would ask the following questions: “Are you a resident of British Columbia?”, “Are you between the ages of 25-60?”, “Do you possess a valid, unrestricted Class 5 British Columbia Driver’s License?”, and “How many years of driving experience do you have?” Only participants aged 25-60 who live in British Columbia and have a full Class 5 license with 10 or more years of driving experience will be included in the study. Those possessing a commercial, trucking, or other higher level driving license will not be included in the study, since their level of licensing infers that they have engaged in more distraction-avoidance training than the average driver. Inclusion of such participants could disrupt the external validity to the average casual driver.

          Volunteers who meet the participation criteria after the initial online screening will then be invited to complete an intake session with the researchers, at which point they will be informed of potential risks and the processes they will undergo and be given the opportunity to provide written consent. During this intake session, participants will also be asked to complete a standardized medical screening questionnaire and simulator sickness screening survey (Reed-Jones, 2011) to assess for potentially increased risks of participation. Individuals with heightened risk due to medical conditions or history of simulator or motion sickness would be excluded from participation (Walker et al., 2021).

Ethical Considerations

          All participation for this study will be voluntary, and participants will be reminded at every stage of the experiment of their right with withdraw without any repercussions. Participants will be offered a gift card to compensate for the gas costs of being involved in this study (totalling $50.00 Canadian). Participants will be informed that they will receive this compensation even if they choose to withdraw from the study, to remove compensatory pressures to remain in the study. Informed consent will first be obtained at the time of the intake screening meeting and will be confirmed upon the participant’s arrival at each of their three simulation sessions. Participants will also be asked to consent to their data being included after the final debrief at the conclusion of the study. Participants’ privacy will be maintained through a coding-system with a protected key that only the lead researcher has access to. Any publications of data will not involve any personal information of participants, only the aggregate data. All participant data will be stored in an offline, password-protected database.

          Exclusion of participants who have potential health-related risks will reduce the potential for harm in this study and ensure that risks for individuals who are included will be low. To reduce psychological and emotional risk-factors, the scripted conversation that the confederates engage in will avoid controversial or potentially triggering topics. Participants will be asked about their driving history, number of accidents involved in, how often they drive, how many passengers they usually have with them while, etc., but will not be excluded from participating due to driving record or driving frequency, since this could lead to unethical systematic exclusion from the research and the potential benefits. Direct benefit for participants is possible since their own results in the study could increase personal awareness of what conversational conditions are safest for them while operating a vehicle. Societal benefit is an increased understanding of what risks are involved with in-car interactions, and ability to educate passengers and drivers on the safest ways of interacting to avoid distraction.

          Deception of the true purpose and of what factors are being measured in the study will be used to prevent confounds; but the risks and procedures involved will be fully disclosed. Following the final treatment session, participants will be debriefed and informed of the true purpose and measures of the study. Participants will be given the opportunity to ask questions about the study and withdraw their data if they wish at this point.


          This study will follow an experimental within-subjects design to assess three levels of the independent variable. This study design was selected because of the large potential for individual differences in driving ability, driving experience, and level of distractibility between different participants. All participants will be required to complete all three levels of the independent variable to have their scores included in the study. The independent variable in this study will be the conversational engagement condition that the participant is engaging with. There will be three different conditions that participants will be asked to undergo: The control condition of having silent passengers in the car, the engaging in conversation condition, and the background conversation condition. From this point on, these conditions will be referred to respectively as “Control” for the silent passengers condition, “Talking” for the engaging in conversation condition, and “Listening” for the background conversation condition. The dependent variable will be the participants’ performance on a simulated driving session, scored based on hazard avoidance and steering skill.

          The order that participants complete these three different conditions will be determined through restricted random assignment to each of the possible orders of completion. Possible orders will be completely counterbalanced, meaning that there are a total of six potential orders that participants could undergo in the format of ABC, ACB, BAC, BCA, CAB, and CBA. The total number of participants will be divided equally between these six potential orders, assignment to completion orders will be carried out through a random from of the orders from a container that holds slips of papers with the number of slots in each treatment order written on individual slips. This complete counterbalancing and restricted randomization process will decrease order-effects as potential confounds by distributing any order effects across the conditions.


          This study will utilize a driving simulation tool with programed routes. The simulator will be designed to closely resemble the interior of an actual car and will have a realistic display. The hazards involved will include pedestrians, cyclists, other vehicles, and environmental factors. The same number of hazards, 15 per drive, will be programed into each route, but in a randomized order. The driving routes will combine a mix of city/urban conditions and residential/suburban conditions.

          The pre-screening questionnaire for health-related risks will be based on the one by Reed-Jones (2011), and the post-study questionnaire will be developed by the researchers. Both of these surveys will be filled out on paper for privacy reasons.


          Participants who have consented to continue with the study and have not been excluded after the health screening process would then be asked to sign up for three one-hour time slots that are at the same time and on the same day for three consecutive weeks. Each session for a participant will take place at the same time to reduce the impact of time-related effects on results. For example, if Participant A completes their first session of one of the conditions at 10:00 AM on Monday, their sessions for completing the other two remaining conditions will also be at 10:00 AM on the next two consecutive Mondays. The order that the participants undergo the conditions will have already been determined through complete counterbalancing and restricted randomization, as outlined above. Participants will not be told the true purpose of the study to avoid potential biases due to expected outcomes but will be debriefed regarding the true purpose directly after their final session to restore trust.

          At each experimental session, the same order of activities will occur, with only the experimental condition that occurs in the being different. This measure will be taken to control for extraneous variables. Participants will arrive, be briefly greeted, and re-confirm consent after reading a brief recap of what will be involved in the session. Following this, the participant will be led to another room, where they will be asked to complete a 20-minute, in-car driving simulation session. This session will occur in the same simulator model and same room each time, to decrease the concern of environmental confounds. The room will have no background noise or music, and minimal items in the room to reduce potential distractions outside of the controlled variables.

          In each condition, there will be two confederates in the vehicle, one sitting in the passenger seat, and one sitting directly behind the driver’s seat. The participant will not know that these passengers are confederates, nor will they know that the conversations follow a script. The conversation script that confederates follow will differ between the conversational and the background conversation conditions, since the participant would likely become aware if the same script was reused. However, both scripts will be similar in nature, avoiding controversial topics or potential triggers, and being fitting for small talk that would occur when first meeting someone. The same background conversation script will be used for all participants. The same initial script will be used for all participants for the conversational condition, but where the conversation leads will depend on how the participant responds and engages with the topic. The confederates in the car will be different people during each of the conditions that a participant undergoes, to avoid an increase in familiarity and comfort with the individuals in the car becoming a confounding variable. In addition to this, all participants will have the same confederates for the same conditions, so if confederate A and B are in the car with participant 1 during the control condition, confederates A and B will be in the car for the control condition for all other participants, to control for differences between repeats of the same condition.

          Participants will be instructed to drive as they would in a real vehicle, to deliver their passengers safely, and to obey the laws of the road. This instruction process could be a potential extraneous variable as it is a reminder of road safety before driving, which does not generally occur in everyday driving situations, however it was important to include so that participants have an idea of what they will be doing and what their goal is. In the control condition, the participants will be instructed not to interact with the passengers. For the listening condition, the participant will be informed that the passengers may converse amongst themselves, but not to engage in conversation with them. In the talking condition, the participant will be told to chat with and respond to the passengers as much as they feel comfortable doing. Before beginning the drive, the participant will have the opportunity to ask the researcher questions about the operation of the simulated vehicle. To avoid bias arising due to expected outcomes, participants will be told that the study is testing for driving performance in people with different levels of experience, and that the passengers are also participating in the study.

          The driver’s performance will be assessed by the amount of time it takes to react to hazards, how well hazards are avoided, and the smoothness of steering and turning motions. These separate factors will be quantified and combined into an overall driving performance score. Each condition will have the same number of hazards during the simulated drive, and the same number of turns, but the order in which these factors are presented will be randomized to avoid participants becoming familiar with the route. One limitation of this study is the fact that there are no measures in place that directly equate driving performance with distraction-related factors; however, the high level of control over numerous other potential factors that would impact driving performance makes this concern manageable.

          Following the 20 minute in-car session, the participant will be taken into another room and asked to fill out a brief questionnaire reflecting on their own perception of their driving performance. Questions will ask about how well the participant thought their driving went, whether it felt safer or less safe than their typical driving on the road, and whether there were any factors that they felt impacted their ability to drive effectively. This questionnaire will not be used as a primary measure of the study, but it will help to give the researchers a clearer picture of the accuracy of participant driving performance scores and the awareness of the participants on their own abilities to drive safely.


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