Holding phone conversations while driving is dangerous not only because it occupies the hands, but also because it requires attention. Where driver and passenger can adapt their conversational behavior to the demands of the situation, and e.g. interrupt themselves when more attention is needed, an interlocutor on the phone cannot adjust as easily. We present a dialogue assistant which acts as 'bystander' in phone conversations between a driver and an interlocutor, interrupting them and temporarily cutting the line during potentially dangerous situations. The assistant also informs both conversation partners when the line has been cut, as well as when it has been reestablished. We show that this intervention improves drivers' performance in a standard driving task.
Talking on the phone while driving introduces risks which may result in accidents
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Other efforts have focused on the potential usefulness of interrupting conversations
when the circumstances on the road require it. In a Wizard-of-Oz experiment, [
In the light cast by these studies, we explore the effects of employing an actual system to achieve this adaptive dynamics in human/human phone conversations: a “bystander” agent that interrupts the conversation in potentially dangerous situations. Subsequently, we test the impact of this system on performance in a driving task. We developed an Interrupting Dialogue Assistant (IDA) which mediates between two participants in a telephone conversation when required by the driving situation. Interruption is triggered by a signal from a component that evaluates the driving situation and judges that the undivided attention of the driver is needed. This immediately cuts the audio line between driver and caller (D and C, respectively). The system then informs D and C about this, as described below. Until it receives a signal indicating that the situation is clear again, the system periodically re-informs C about the line status, and also suppresses any attempts to speak. Finally, it notifies D and C when the line is open again.
The states of the system are shown in Figure 1 in a diagram, with events that
trigger transitions, as well as the actions performed by the system at each one of these
transitions.
Informing the Caller The system informs the caller of the state of the interaction
(line open / closed) through a set of utterances which are synthesized with MaryTTS3
[
– Resuming the conversation: On receiving the appropriate signal, the system announces that the line is open again.
Das Gespräch muss einige Sekunden unterbrochen The conversation has to be interrupted for a few werden. seconds.
Ihr Gesprächspartner ist gerade wieder beschäftigt. Your conversational partner is busy again. Diese Unterhaltung muss nochmal kurz pausiert wer- This conversation needs to be paused briefly den. again.
Bitte eine Sekunde mehr Geduld. Please be patient for one more second. Ihr Gesprächspartner kann Sie noch nicht hören. Your conversational partner can’t hear you yet. Die Leitung ist bald wieder offen. The line will soon be reconnected.
prompt) Moment bitte. One moment, please. Noch nicht. Not yet. Bitte warten. Please wait.
Sie können weiter sprechen. You can go on speaking.
Jetzt kann der Fahrer wieder hören The driver can now hear you again.
Die Unterhaltung geht jetzt weiter The conversation now continues.
Informing the Driver The system also provides information to the driver, although
it does so in a different way. Interruption of the audio line is communicated through a
bell sound instead of verbally, as we considered that additional speech would be more
distracting than a sound [
Driving Task To test driving performance, we use a variant of the standard Lane
Change Task (LCT) [
driving speed was 40 km/h and the maximum possible speed was 70 km/h. The driving equipment consisted of a 40-inch 16:9 screen and a Thrustmaster PC Racing Wheels Ferrari GT Experience steering wheel and pedal.
Speaking Task To ensure that a lively, continuous conversation would take place between our experiment participants (driver and caller), we instructed them to engage in a role play activity. They were provided with discussion topics beforehand, and instructed to express opposing opinions about them, i.e. to contradict each other. Discussion topics were selected to be related to the experience and interests of the subject population (university students) and to be engaging but not extremely sensitive. The caller was given responsibility for the flow of the discussion and instructed to keep it as entertaining as possible and to switch between topics when necessary. 2.3
To effectively evaluate our hypothesis that an assistant such as the one described above would result in better driving, we designed three experimental conditions: NO-TALK Driving only (control condition; including lane changes), no conversation UNINTERRUPTED Simultaneous driving (including lane changes) and conversation. INTERRUPTED Simultaneous driving and conversation, but the latter gets interrupted as soon as a lane change is announced and resumed when this maneuver is completed. The conditions were presented in blocks, as shown in Figure 3. The first block was always NO-TALK, whereas the order of the second and third conditions varied: For half of the participants, the second block corresponded to the UNINTERRUPTED condition and the third one, to the INTERRUPTED condition whereas, for the other half, these two blocks were inverted. Each of the three blocks lasted approximately 10 minutes and was made up of 11 trials: three practice trials and eight experiment trials. Only experiment trials are considered in the results.
The approximate duration of a whole experiment was 40 minutes. Before each
phase, participants were given instructions. After completion of all three phases, they
filled out a questionnaire. Finally, they swapped roles (the caller became the driver and
viceversa) and the whole process was repeated.
Sixteen subjects participated in the study, which results in eight pairs participating twice
each (due to role-swapping). Driver and caller were placed in two separate rooms, and
audio was sent between them through networked computers via Robotic Service Bus
[RSB] [
The interrupter was developed using the control component of OpenDial [
The total number of trials recorded was 528: eleven in each of the three conditions, for each of the 16 participants. We excluded training trials from the analysis of driving performance, which left us with 384. In addition, it was necessary to exclude some episodes where the driver never reached the target lane, since this made it impossible to calculate lane-changing time. This resulted in 365 trials useable for analysis. Furthermore, given that two of the road lanes are adjacent to the middle whereas the other two (the external lanes) are not, some further episodes had to be excluded in order to ensure an equal number of changes to adjacent and non-adjacent lanes in all conditions. This left us with 342 trials: 114 for each condition, out of which 64 were changes to adjacent lanes and 50, to non-adjacent ones.
There were eleven interruptions for each driver-caller pair: Three correspond to the training phase and eight, to the experiment trials. Out of a total of 176 interruptions for the 16 participants, the driver was speaking at the moment of the interruption in 75 instances and the caller, in 88; both were speaking simultaneously in three cases, and both were silent in 10 cases. From the moment when callers started hearing the interruption prompt, it took them an average of 1.01 seconds to stop talking (SD 1.07). In addition, the caller spoke during the interrupted phase and was told by the system to wait in 26 instances. When callers were interrupted, they left the ongoing word incomplete in 22.7% of the cases, finished the word but left an incomplete syntactic clause in 34.1%, and produced a full clause in 43.2%. The mean duration of the interrupted periods (from the interruption prompt to the resumption prompt) was 11.321 seconds (SD 0.637); this was, of course, subject to how fast the driver was able to complete the maneuver. 3.2
For every trial, we calculated lane changing time, which we defined as the time from the moment the lane changing signal appears until the driver reaches the target lane. Lane changing times were almost half a second shorter for the INTERRUPTED condition (4.059 s., SD 1.349) than for the NON-INTERRUPTED condition (4.552 s., SD 1.646), i.e. drivers were able to complete the change faster when the interrupter was employed. This difference is significant (t-test, t(15) = 3.37, p< 0.01). On the other hand, no statistically significant difference was found between lane changing times in the INTERRUPTED and in the NO-TALK (4.381 s., SD 1.423) conditions, which shows performance when the interrupter was employed was as fast as during the driving-only task, in which no speech was involved. These results can be interpreted as suggesting that our interrupting assistant enabled drivers to complete lane changes sooner by granting them the possibility to concentrate only on the driving, which would constitute an advantage in real life, since swiftness is normally associated with minimization of risks in overtaking maneuvers. On the other hand, it is also possible that the presence of an auditory stimulus (the bell) simultaneous with the visual lane changing signal (the arrow) might have contributed to a faster reaction in the interrupted condition than in the non-interrupted one, in which the moment to change lanes is only announced visually. 3.3
At the end of each phase of the experiment, participants filled out a questionnaire, rating how pleasant they had found the interruptions, on a scale with 1 meaning extremely unpleasant and 5 meaning extremely pleasant. They rated both the experience of being interrupted as caller and that of being interrupted as driver. The results are shown in Figure 4. Whereas ratings for drivers were varied (M = 2.94, SD = 0.97), the majority of subjects rated the interruptions for the caller as a 2 (M = 2.13, SD = 0.7), and hence were more unanimously displeased with them.
In an open post-experiment question, some participants suggested that other interruption modes (such as a sound signal only), interruption manners (with more forewarning), or interruption utterances might be more acceptable. This remains to be evaluated.
12 10 s te 8 o v fo 6 r e b m4 u N 2 It is also important to note that interruptions leave callers temporarily without any tasks to perform, whereas drivers still have their main task to concentrate on: This could also be a reason why callers get more frustrated by interruptions. Finally, pleasantness scores for drivers were correlated neither with number of successful trials nor with the frequency with which the driver had been interrupted (as opposed to the caller). 4
The results presented show that verbal interjections coming from a system do efficiently interrupt an ongoing conversation. They also show that, in a driving situation, doing so improves performance during difficult driving tasks. Further research needs to be done in order to better understand its influence on performance and to find ways in which it can be enhanced. It is essential to cast more light on users’ emotional responses to these interruptions (as callers as well as drivers) and to find ways to minimize frustration and stress.
The feedback obtained through the questionnaires raises issues regarding both the content and the mode of interruptions. Among the suggestions, it is possible to identify two trends: Some participants recommended being more explicit as to the reasons behind the need for the interruption, whereas others suggested ideas which might appear (at least initially) precisely the opposite, such as shortening the utterances or using a sound signal instead of speech. Exploration of these different strategies and their effects on users will be a next step. Furthermore, it might be possible to combine these seemingly opposed suggestions, for example by producing shorter utterances which still convey more precise information about the situation of the driver (driver overtaking, please wait) or sounds which stand for specific driving events.
Secondly, it is necessary to explore ways in which speakers can be helped, when
resuming the conversation, to remember what was being said before they were
interrupted. This kind of assistance might also be beneficial for driving performance, as
some drivers in our experiment reported that they had to make a considerable effort
during interrupted lane changes to keep the state of the conversation in their minds. It
might here prove beneficial to monitor the speaker’s production and, depending on the
severity of the danger situation, decide whether to interrupt as soon as the alert signal
becomes available or to wait for a specific moment in the dialogue, such as a
transitionrelevance place [
Finally, some participants reported a desire for increased control over the system, for
example by giving drivers the possibility to activate the interruptions themselves. This
is related to [
This work was supported by the Cluster of Excellence Cognitive Interaction Technology ‘CITEC’ (EXC 277) at Bielefeld University, which is funded by the German Research Foundation (DFG). We gratefully acknowledge Sina Zarrieß’s help with results and her always insightful remarks, Oliver Eickmeier’s assistance with scenario generation and Robert Eickhaus’ help with recording the interactions. Finally, thanks to Julian Hough, Ting Han and Spyros Kousidis for valuable discussions and tips.