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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <title>A longitudinal analysis of the effectiveness of California’s ban on cellphone use while driving</title>
      <link>https://trid.trb.org/View/1605864</link>
      <description><![CDATA[Cellphone use while driving is an increasingly serious threat for traffic safety and is prohibited in many jurisdictions. In California, the use of handheld cellphones while driving has been prohibited since July 1, 2008. Using interrupted time series analysis, this study explores the effectiveness of the ban by specifically analyzing the crashes caused by cellphone usage in California from 2002 to 2014. These crashes were thought to be able to reflect the role of the ban more accurately than total crashes. The ban was found effective in reducing the cellphone usage-caused crashes in terms of both crash frequency and crash proportion. The study also confirms that crashes caused by cellphone use produce more severe outcomes than other crashes. These findings show that the ban on handheld cellphone use while driving plays an important role for improving traffic safety in California. In addition, it is found that the ban motivates drivers to switch from handheld cellphones to hands-free cellphones, but in terms of crash severity, hands-free cellphone usage and handheld cellphone usage do not show significant differences. These findings support a complete ban on cellphone use while driving--not just a prohibition of handheld cellphone use. The study results are expected to provide new insights for future policy-making related to cellphone use while driving.]]></description>
      <pubDate>Tue, 21 May 2019 11:06:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/1605864</guid>
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      <title>Modelling the Effect of Mobile Phone Use on Driving Behaviour Considering Different Use Modes</title>
      <link>https://trid.trb.org/View/1596868</link>
      <description><![CDATA[Mobile phone use while driving is a major cause of driver distraction, affecting driving performance and increasing accident risk. Governments have responded to this with the implementation of legislation prohibiting the use of mobile phones, under specific conditions, mainly adopting the hands-free use. Still, mobile phone is a cause of several types of distraction rather than just manual. This study explores the effect of mobile phone use while driving via a simulator experiment. Participants drive under various types of mobile phone use mode- namely, handheld, hands-free (wired earphone), and speaker to capture this effect. Results highlight the effect of mobile phone use, regardless of the use mode, on driving behavior through specific indicators: maximum driving speed, reaction time, and lateral position. In particular, considering the aforementioned parameters the handheld mode demonstrates safer driving behavior compared to the speaker mode. The results of this study stress the need for a reconsideration of the present legislation.]]></description>
      <pubDate>Tue, 23 Apr 2019 15:20:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/1596868</guid>
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      <title>An eye-tracking study on the road examining the effects of handsfree phoning on visual attention</title>
      <link>https://trid.trb.org/View/1574704</link>
      <description><![CDATA[One well documented source of distraction in traffic is phoning. The negative effect of phoning is not only attributed to the effects of operating the device, but it is also caused by the division of attention between driving and the conversation. Therefore, one could argue that handsfree phoning is not per se safer than handheld phoning. Indeed, a number of studies has indicated that handsfree phoning and handheld phoning produce the same performance deficits. In the present study, the authors examine the effects of handsfree phoning on eye-movement patterns while driving in traffic. Thirty participants made two consecutive trips of about 14 km on a three-lane highway. During one of these two trips, they received a phone call on a handsfree device in the vehicle. The analysis of the eye-tracking variables indicate that road signs, other vehicles, and the speedometer are fixated less. At the same time, the visual scan pattern suggests a wider spatial distribution of eye fixations during a handsfree phone call. Taken together, these findings seem to suggest that during handsfree phoning, the gaze behavior is determined to a lesser degree by the driving task; drivers seem to fixate less on traffic related information. However, future research is needed to provide further evidence to confirm this conclusion and to investigate if (or under which conditions) these differences will actually result in less safer driving when phoning handsfree.]]></description>
      <pubDate>Fri, 25 Jan 2019 10:34:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1574704</guid>
    </item>
    <item>
      <title>Effects of hands-free cellular phone conversational cognitive tasks on driving stability based on driving simulation experiment</title>
      <link>https://trid.trb.org/View/1519819</link>
      <description><![CDATA[Driver distraction due to cellular phone usage is a major contributing factor to road crashes. This study compares the effects of conversational cognitive tasks using hands-free cellular phone on driving performance under three distraction conditions: (1) no distraction (no cellular conversation), (2) normal conversation (non-emotional cellular conversation), and (3) seven-level mathematical calculations. A car-following scenario was implemented using a driving simulator. Thirty young drivers with an average age of 24.1 years maintained a constant speed and distance between the subject vehicle and a leading vehicle on the driving simulator, and then respond to the leading vehicle’s emergency stop. The driving performances were assessed by collecting and statistically analyzing several variables of maneuver stability: the drivers’ brake reaction times, driving speed fluctuation, car-following distance undulation, and car-following time-headway undulation. The results revealed that normal conversation on a hands-free cellular phone impaired driving performance. The degree of impairment caused by normal calculation was equivalent to the distraction caused by Level 3 mathematical calculations according to the seven-level calculation baseline. The calculation difficulty of Level 3 is one double-digit figure plus a single-digit figure, and non-carry addition mental arithmetic is required, e.g., 44 + 4. The results indicated that an increase in the level of complexity of the calculation task was associated with an increase in brake reaction time. The seven-level calculation-task baseline could be applied to measure additional distraction effects on driving performance for further comparison.]]></description>
      <pubDate>Thu, 19 Jul 2018 14:45:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/1519819</guid>
    </item>
    <item>
      <title>Distracted Driving Behaviors and Beliefs among Older Adults</title>
      <link>https://trid.trb.org/View/1495150</link>
      <description><![CDATA[Distracted driving, and especially cell phone use, is a prevalent contributor to crashes. Older drivers have an increased risk of committing safety errors while driving, especially with distraction. The objective of this study was to characterize phone-related distractions in older drivers (age > 65) and identify intervention strategies likely to reduce cell distraction. A 64-question survey was offered online and on paper. A distracted driving scale (DDS) was created by summing responses on 11 distracted driving questions related to phone use (possible score range 0 to 44). Linear regression was performed to identify variables associated with a higher DDS score. A total of 363 older drivers completed the survey; the mean age was 73 and 56% were female. 60% of older adults reported using their cell phone while driving at least some of the time. Participants perceived their own ability as capable or very capable when driving and using: handheld phone (40%); hands-free phone (78%); other tasks (38%) while driving. 32% of older adults who drive minors reported driving while distracted. 30% of those who work felt obligated to take work-related calls. Variables associated with distracted driving include younger age, driving more miles, perceived hands-free skill, smart phone ownership, and being employed or self-employed. State laws and potential loss of insurance coverage with distracted driving were cited as effective penalties. Older adults are engaging in distracted driving, including with minors in the car. Education, state laws, and altering insurance coverage may mitigate this behavior.]]></description>
      <pubDate>Mon, 26 Mar 2018 14:31:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/1495150</guid>
    </item>
    <item>
      <title>Steering the Conversation: A Linguistic Exploration of Natural Language Interactions with a Digital Assistant during Simulated Driving</title>
      <link>https://trid.trb.org/View/1466942</link>
      <description><![CDATA[Given the proliferation of ‘intelligent’ and ‘socially-aware’ digital assistants embodying everyday mobile technology – and the undeniable logic that utilising voice-activated controls and interfaces in cars reduces the visual and manual distraction of interacting with in-vehicle devices – it appears inevitable that next generation vehicles will be embodied by digital assistants and utilise spoken language as a method of interaction. From a design perspective, defining the language and interaction style that a digital driving assistant should adopt is contingent on the role that they play within the social fabric and context in which they are situated. The authors therefore conducted a qualitative, Wizard-of-Oz study to explore how drivers might interact linguistically with a natural language digital driving assistant. Twenty-five participants drove for 10 min in a medium-fidelity driving simulator while interacting with a state-of-the-art, high-functioning, conversational digital driving assistant. All exchanges were transcribed and analysed using recognised linguistic techniques, such as discourse and conversation analysis, normally reserved for interpersonal investigation. Language usage patterns demonstrate that interactions with the digital assistant were fundamentally social in nature, with participants affording the assistant equal social status and high-level cognitive processing capability. For example, participants were polite, actively controlled turn-taking during the conversation, and used back-channelling, fillers and hesitation, as they might in human communication. Furthermore, participants expected the digital assistant to understand and process complex requests mitigated with hedging words and expressions, and peppered with vague language and deictic references requiring shared contextual information and mutual understanding. Findings are presented in six themes which emerged during the analysis – formulating responses; turn-taking; back-channelling, fillers and hesitation; vague language; mitigating requests and politeness and praise. The results can be used to inform the design of future in-vehicle natural language systems, in particular to help manage the tension between designing for an engaging dialogue (important for technology acceptance) and designing for an effective dialogue (important to minimise distraction in a driving context).]]></description>
      <pubDate>Fri, 26 May 2017 11:32:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/1466942</guid>
    </item>
    <item>
      <title>Handheld and Hands-Free Cell Phone Use Amongst Drivers with Hands-Free Technology</title>
      <link>https://trid.trb.org/View/1394088</link>
      <description><![CDATA[To address safety concerns of handheld phone use while driving, several hands-free cell phone technologies have been developed for use while driving. The current study investigated drivers’ use of these hands-free cell phones. The naturalistic driving data were collected in 2011 from 204 participants who reported using a cell phone while driving at least once per day. Drivers drove their own vehicles, which had been instrumented for data collection, and participated on average for 31 days. Drivers also provided cell phone records, which were overlaid with the naturalistic data and used to determine when cell phone use occurred while driving. The data were first analyzed in the NHTSA study titled “The Impact of Hand-held and Hands-free Cell Phone Use on Driving Performance and Safety-Critical Event Risk.” In the current study, it was found that drivers with hands-free cell phones were observed to use a hand-held phone more frequently than hands-free phones in call initiation subtasks. Call initiation subtasks on a handheld phone often involve several visual-manual components that require a driver to look away from the forward roadway, and therefore, it is concerning that drivers are choosing a handheld phone over a hands-free phone for this task. Use of a hands-free cell phone did change in certain environmental conditions, but no demographic conditions were found to be associated with changes in hands-free cell phone use.]]></description>
      <pubDate>Mon, 07 Mar 2016 10:19:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/1394088</guid>
    </item>
    <item>
      <title>Drivers' Visual Behavior When Using Handheld and Hands-Free Cell Phones</title>
      <link>https://trid.trb.org/View/1370404</link>
      <description><![CDATA[This study investigated driver distraction and how the use of handheld (HH), portable hands-free (PHF), and integrated hands-free (IHF) cell phones affected the visual behavior of motor vehicle drivers.  A naturalistic driving study recorded 204 participating drivers using video cameras and vehicle sensors for an average of 31 days. A total of 1564 cell phone calls made and 844 text messages sent while driving were sampled and underwent a video review. Baselines were established by recording epochs prior to the cell phone interactions. Total eyes-off-road time (TEORT) was examined to assess the visual demands of cell phone subtasks while driving. Percent TEORT was reported and compared against the baseline.  Visual-manual subtasks performed on HH, PHF, and IHF cell phones were found to significantly increase drivers' mean percent TEORT. In contrast, conversing on an HH cell phone was found to significantly decrease drivers' mean percent TEORT, indicating that drivers looked at the forward roadway more often. No significant differences in percent TEORT were found for drivers conversing using PHF or IHF cell phones. The mean TEORT durations for visual-manual subtasks performed on an HH cell phone were significantly longer than the mean TEORT durations on either IHF or PHF cell phones. This research helps to further reinforce the distinction made between handheld and hands-free cell phone use in transportation distraction policy.]]></description>
      <pubDate>Fri, 23 Oct 2015 09:37:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1370404</guid>
    </item>
    <item>
      <title>Frequency and impact of hands-free telephoning while driving – Results from naturalistic driving data</title>
      <link>https://trid.trb.org/View/1344855</link>
      <description><![CDATA[The frequency and impact of hands-free telephoning while driving was analyzed based on naturalistic driving data from 106 drivers. The results from naturalistic driving data were compared with the results from experimental approaches. The implication of the overall results and the differences across drivers are discussed. Continuous information on the usage of the hands-free phone equipment was available which made it possible to include the entire database (~1 000 000 km) in a completely automatized analysis. Results show that drivers talked on a hands-free phone about 11% of driving time. There were large differences across drivers in the frequency and usage of a hands-free phone. While telephoning, an adaptation of driving behavior could be found. Drivers slowed down and increased their distance to the lead vehicle. Furthermore, during telephoning, an overall reduction of potentially critical driving situations was found. Overall, the results indicate that compensation for telephoning was carried out with a long-term change of driving behavior, rather than with a short term adaption to the situation.]]></description>
      <pubDate>Mon, 23 Mar 2015 08:59:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1344855</guid>
    </item>
    <item>
      <title>Texting while driving: Is speech-based text entry less risky than handheld text entry?</title>
      <link>https://trid.trb.org/View/1324760</link>
      <description><![CDATA[Research indicates that using a cell phone to talk or text while maneuvering a vehicle impairs driving performance. However, few published studies directly compare the distracting effects of texting using a hands-free (i.e., speech-based interface) versus handheld cell phone, which is an important issue for legislation, automotive interface design and driving safety training. This study compared the effect of speech-based versus handheld text entries on simulated driving performance by asking participants to perform a car following task while controlling the duration of a secondary text-entry task. Results showed that both speech-based and handheld text entries impaired driving performance relative to the drive-only condition by causing more variation in speed and lane position. Handheld text entry also increased the brake response time and increased variation in headway distance. Text entry using a speech-based cell phone was less detrimental to driving performance than handheld text entry. Nevertheless, the speech-based text entry task still significantly impaired driving compared to the drive-only condition. These results suggest that speech-based text entry disrupts driving, but reduces the level of performance interference compared to text entry with a handheld device. In addition, the difference in the distraction effect caused by speech-based and handheld text entry is not simply due to the difference in task duration.]]></description>
      <pubDate>Wed, 29 Oct 2014 11:38:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1324760</guid>
    </item>
    <item>
      <title>Evaluating the Effectiveness of the Law Banning Handheld Cellphone Use While Driving</title>
      <link>https://trid.trb.org/View/1322903</link>
      <description><![CDATA[Cellphone use while driving is one of the major concerns in traffic safety, and numerous research studies have found that cellphone use while driving can increase traffic collision risk. With growing popularity of cellphone use, many states in the United States enacted the law banning handheld cellphone use while driving in recent years. However, there is a debate on effectiveness of the law. In this study, we analyze the six-year collision data between 2006 and 2010 in the state of California to examine the timing of a significant change in the trend of cellphone related collisions. The authors adopt the turning point analysis technique without imposing a prior belief on whether or when such a change has occurred. Both the frequentist and Bayesian approaches are applied to four different groups, including the all cellphone collision group and three subgroups characterized by cellphone usage. The result shows that the turning point coincides with the timing of enforcement of the handheld law in California, except for the subgroup containing hands-free related collisions only. The authors applied the same method to two confounding factors including driving under influence and CD/radio use, and find that the turning points do not agree with the cellphone related collisions. Although a more comprehensive set of confounding factors needs to be considered to establish a causal relationship between the handheld law and cellphone related collisions, coincidence between the handheld law and the turning point suggests that the law should be considered as one of the primary factors in cellphone related collisions reduction.]]></description>
      <pubDate>Mon, 13 Oct 2014 08:58:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1322903</guid>
    </item>
    <item>
      <title>Distracted Driving and Perceptions of Hands-Free Technologies: Findings from the 2013 Traffic Safety Culture Index</title>
      <link>https://trid.trb.org/View/1279710</link>
      <description><![CDATA[An analysis of the 2012 Traffic Safety Culture Index distraction data found that while 66% of licensed drivers believed motorist use of hand-held cell phones was somewhat or completely unacceptable, more than half (56.2%) believed using hands-free devices was somewhat or completely acceptable. This is consistent with the fact that nearly three quarters said they believed hands-free devices were somewhat or much safer than their hand-held counterparts. This general public perception has been matched by a proliferation of increasingly sophisticated speech-based infotainment and communications systems in new vehicles - many of which are marketed as safe by virtue of being hands-free - as well as a lack of legislative or regulatory action against driver use of hands-free technologies. However, a June 2013 study by the AAA Foundation and the University of Utah affirming earlier studies, challenged the public perception, and concluded that “hands-free” does not mean “risk-free,” due to the effects of cognitive distraction. Contrary to prevailing assumptions, conversing on a hands-free phone produced the same amount of mental workload as did using a hand-held device, and driver interaction with an entirely hands-free in-vehicle email system produced the highest level of cognitive distraction. In light of this, the AAA Foundation expanded its slate of questions for the 2013 safety culture survey that pertained to distracted driving, hands-free communications, and voice-activated and other in-vehicle technologies. The objective was to gain a deeper understanding of public perceptions of cognitive distraction and the hands-free debate, and  investigate whether there have been any changes over the past year in these areas.]]></description>
      <pubDate>Mon, 23 Dec 2013 07:53:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/1279710</guid>
    </item>
    <item>
      <title>Driver Distraction and Hands-Free Texting While Driving</title>
      <link>https://trid.trb.org/View/1248973</link>
      <description><![CDATA[Distracted driving has become a source of growing concern among governments, road safety researchers and the public in the past decade. This is due, in part, to concern that distracted driving contributes to increased crash risk, and, in part because of the link that has been established between at least some types of distractions and increased crash risk.  In particular, research clearly demonstrates that texting while driving is an unsafe behavior because texting is a significant source of distraction. This behavior is especially problematic for teen drivers who are more often attracted to and more readily adopt new communication technologies. The increased relative risk of teen and young drivers being involved in a distraction-related collision can be attributed to behavior and attitudes among this age group. The crash risk associated with hands-free texting while driving is not as well understood because in-car voice-to-text technology is relatively new, and few studies investigating this specific issue have been completed to date. What is known, however, supports the contention that hands-free texting while driving poses significant distraction, and consequently, unacceptable crash risk. To put this traffic safety issue and public health concern into perspective, this paper draws upon existing research in order to share insight into key facets of distracted driving and the implications for texting while driving behavior among young drivers.]]></description>
      <pubDate>Fri, 17 May 2013 12:33:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/1248973</guid>
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    <item>
      <title>The Impact of Hand-Held and Hands-Free Cell Phone Use on Driving Performance and Safety-Critical Event Risk</title>
      <link>https://trid.trb.org/View/1249880</link>
      <description><![CDATA[This study investigated the effects of distraction from the use of three types of cell phones: (1) hand-held (HH), (2) portable handsfree (PHF), and (3) integrated hands-free (IHF). Through a naturalistic driving study (NDS), 204 drivers were continuously recorded for an average of 31 days. Only drivers who reported talking on a cell phone while driving at least once per day were recruited. A key feature was that drivers provided their cell phone records for analysis, making this the first NDS to date to combine call and text records with continuous naturalistic driving data. Results show that drivers talked on a cell phone 10.6 percent of the time the vehicle was in operation (28% of all calls and 10% of all text messages occurred while the vehicle was being operated). Talking on a cell phone, of any type, while driving was not associated with an increased safety-critical event (SCE) risk. SCEs comprised crashes, near-crashes, and crash-relevant conflicts. Visual-manual (VM) subtasks performed on an HH cell phone, however, were associated with an increased SCE risk. HH cell phone use in general was thus found to be associated with an increased SCE risk. In contrast, PHF and IHF cell phone use, absent of any VM HH cell phone subtasks, were not found to be associated with an increased SCE risk. However, VM HH cell phone subtasks were frequently observed during hands-free cell phone use. Driver performance when using a cell phone was also investigated through a within-subject comparison. VM HH cell phone subtasks were found to significantly increase the percentage of time drivers took their eyes off the forward roadway, while talking on an HH cell phone significantly decreased the percentage of time drivers took their eyes off the forward roadway. The effects of cell phone use on vehicle control were less pronounced.]]></description>
      <pubDate>Thu, 09 May 2013 14:15:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1249880</guid>
    </item>
    <item>
      <title>An Evaluation of the Effectiveness of Voice-To-Text Programs at Reducing Incidences of Distracted Driving</title>
      <link>https://trid.trb.org/View/1247909</link>
      <description><![CDATA[Text messaging is no longer limited to manual-entry. There are several mobile applications that aim to assist the driver in sending and receiving text messages by incorporating a voice-to-text component. To date, there has been no published research that evaluates the impact of voice-to-text mobile applications on driver behavior and safety. To address this issue, 43 participants drove an instrumented vehicle on a closed course for a baseline as well as three texting conditions: manual-entry, using Siri, and using Vlingo. Results indicate that driver reaction times were nearly two times slower than the baseline condition, no matter which texting method was used. Eye gazes to the forward roadway also significantly decreased compared to baseline, no matter which texting method was used. Additionally, it took drivers longer to complete the same texting task using the voice-to-text applications than it did when texting manually, though Siri produced the fewest errors. Self-assessment feedback revealed that participants felt less safe using any of the three texting methods compared to the baseline, but felt safer using either voice-to-text application than when manually texting. These results have immediate implications for improving our understanding of the dangers of texting while driving and the potential safety improvements of using voice-to-text options.]]></description>
      <pubDate>Fri, 19 Apr 2013 13:19:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/1247909</guid>
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