In the signal planning process, the ERTMS speed profiles based on track nature needs to be complemented with additional constraints. The base profile resolving the allowed track speed, often includes several speed changes which can be difficult for the train driver to follow. One approach to deal with this problem is to filter the base profile, reducing the number of changes and giving the driver more time for attention.This paper presents the effects of a speed profile filtering principle, based on possible time usage during a speed increase, on train energy consumption, train driver braking behavior, running time, and driver workload. In an Electrical Multiple Unit train driver simulator, 40 drivers tested three different speed profiles of a 19 km railway line. It can be concluded that differences in running time are small, that these small time-gains implies a high energy con-sumption cost, and that drivers tend to drive close to the indication braking curve in the beginning of the braking phase. Further, the drivers rated the driver task workload low for all filter conditions. Accordingly, a certain filter level is required to get capacity and energy effects.

Purpose

To examine eye tracking data and compare visual behavior in individuals with normal hearing (NH) and with moderate hearing loss (HL) during two types of driving conditions: normal driving and driving while performing a secondary task.

Methods

24 participants with HL and 24 with NH were exposed to normal driving and to driving with a secondary task (observation and recall of 4 visually displayed letters). Eye movement behavior was assessed during normal driving by the following performance indicators: number of glances away from the road; mean duration of glances away from the road; maximum duration of glances away from the road; and percentage of time looking at the road. During driving with the secondary task, eye movement data were assessed in terms of number of glances to the secondary task display, mean duration of glances to the secondary task display, and maximum duration of glances to the secondary task display. The secondary task performance was assessed as well, counting the number of correct letters, the number of skipped letters, and the number of correct letters ignoring order.

Results

While driving with the secondary task, drivers with HL looked twice as often in the rear-view mirror than during normal driving and twice as often as drivers with NH regardless of condition. During secondary task, the HL group looked away from the road more frequently but for shorter durations than the NH group. Drivers with HL had fewer correct letters and more skipped letters than drivers with NH.

Conclusions

Differences in visual behavior between drivers with NH and with HL are bound to the driving condition. Driving with a secondary task, drivers with HL spend as much time looking away from the road as drivers with NH, however with more frequent and shorter glances away. Secondary task performance is lower for the HL group, suggesting this group is less willing to perform this task. The results also indicate that drivers with HL use fewer but more focused glances away than drivers with NH, they also perform a visual scan of the surrounding traffic environment before looking away towards the secondary task display.

The aim of this PhD thesis was to investigate traffic safety and mobility for individuals with hearing loss (HL). Three studies were conducted: 1. a questionnaire survey aimed to evaluate differences in choice of transportation that might be related to HL, 2. a driving simulator study that looked into compensatory strategies and evaluated the efficiency of a tactile signal to alert the driver, and 3. a field study to evaluate these effects in real traffic and to evaluate a navigation system with a supportive tactile signal. The effects of HL discovered in this thesis add to the knowledge and understanding of the influence of HL on traffic safety and mobility. Differences found consistently point to a generally more cautious behavior. Compensatory and coping strategies associated with HL are bound to driving complexity and appear when complexity increases. These strategies include driving at lower speeds, using a more comprehensive visual search behavior and being less engaged in distracting activities. Evaluation of a tactile signal showed that by adding a tactile modality, some driver assistance systems can also be made accessible to drivers with HL. At the same time, the systems might be more effective for all users, since the driver can be more focused on the road. Based on the results in this thesis, drivers with HL cannot be considered an increased traffic safety risk, and there should be no need for adjustments of the requirements of hearing for a license to drive a car.

Purpose

To compare the effect of cognitive workload in individuals with and without hearing loss, respectively, in driving situations with varying degree of complexity.

Methods

24 participants with moderate hearing loss (HL) and 24 with normal hearing (NH) experienced three different driving conditions: Baseline driving; Critical events with a need to act fast; and a Parked car event with the possibility to adapt the workload to the situation. Additionally, a Secondary task (observation and recalling of 4 visually displayed letters) was present during the drive, with two levels of difficulty in terms of load on the phonological loop. A tactile signal, presented by means of a vibration in the seat, was used to announce the Secondary task and thereby simultaneously evaluated in terms of effectiveness when calling for driver attention. Objective driver behavior measures (M and SD of driving speed, M and SD of lateral position, time to line crossing) were accompanied by subjective ratings during and after the test drive.

Results

HL had no effect on driving behavior at Baseline driving, where no events occurred. Both during Secondary task and at the Parked car event HL was associated with decreased mean driving speed compared to baseline driving. The effect of HL on the Secondary task performance, both at Baseline driving and at the lower Difficulty Level at Critical events, was more skipped letters and fewer correctly recalled letters. At Critical events, task difficulty affected participants with HL more. Participants were generally positive to use vibrations in the seat as a means for announcing the Secondary task.

Conclusions

Differences in terms of driving behavior and task performance related to HL appear when the driving complexity exceeds Baseline driving either in the driving task, Secondary task or a combination of both. This leads to a more cautious driving behavior with a decreased mean driving speed and less focus on the Secondary task, which could be a way of compensating for the increasing driving complexity. Seat vibration was found to be a feasible way to alert drivers with or without HL.

An on-road study was conducted to evaluate a complementary tactile navigation signal on driving behaviour and eye movements for drivers with hearing loss (HL) compared to drivers with normal hearing (NH). 32 participants (16 HL and16 NH) performed two preprogrammed navigation tasks. In one, participants received only visual information, while the other also included a vibration in the seat to guide them in the correct direction. SMI glasses were used for eye tracking,recording the point of gaze within the scene. Analysis was performed on predefined regions. A questionnaire examined participant's experience of the navigation systems. Hearing loss was associated with lower speed, higher satisfaction with the tactile signal and more glances in the rear view mirror. Additionally, tactile support led to less time spent viewing the navigation display.

Purpose

To examine how road users with different degree of hearing loss experience safety and mobility in transport situations, compared to road users with normal hearing.

Methods

A questionnaire study was conducted with participants recruited from the local branch of The Swedish hard of hearing society. A normal hearing control group, matched on age, gender and geographical location, was selected from a commercial database. The response rate was 35 % (n = 194) in the group with Hearing Loss (HL) and 42 % (n = 125) in the group with Normal Hearing (NH). The individuals with hearing loss were grouped into four groups according to the degree of their hearing loss (mild, moderate, severe and profound).

Results

Hearing loss affected some specific aspects regarding transport situations, while others remained unaffected. Individuals with hearing loss were not as likely to have a driving license, but for those who have, hearing loss had no effect on mileage per year. Loss of hearing had an effect on criteria for choosing mode of transportation, but in the aggregate, no difference between the groups could be shown in the distribution of how much each mode of transportation was used. With a few exceptions, hearing loss did not affect the ratings of importance of hearing for different transportation modes. Hearing loss affected most questions regarding hearing and driver abilities, while avoidance of specific traffic situations was not associated with hearing loss. Hearing loss had only minor effects on the factors causing inattention when driving, and on the interest in a warning system for driver inattention. The interest in a warning system for driver inattention was high regardless of hearing category.

Conclusions

Hearing loss influences the prevalence of driving license and criteria for choosing mode of transportation, however has no effect on the distribution of how much each mode of transportation was used. In general, in this study, respondents with higher degree of hearing loss were less concerned about the effect of hearing loss, indicating that they might be using coping strategies. The interest in warning system for inattention and the attitude towards strengthening of auditory information in traffic situations is high regardless of hearing category. This suggests further research on coping strategies and on design of support systems accessible for drivers with hearing loss.

Objective: To examine how road users with different degree of hearing loss experience safety and mobility in transport situations compared to road users without hearing loss.

Methods: The participants were recruited from the local branch of HRF. A hearing control group, matched on age, gender and geographical location, was selected from a commercial database. The individuals with hearing hearing-loss were grouped into four groups according the degree of their hearing-loss.

Results: Hearing loss affects some specific aspects regarding transport situations, while others remain unaffected. Individuals with hearing loss are not as likely to have a driving license, but for those who have, hearing loss has no effect on mileage per year. Loss of hearing has an effect on criteria for choosing transportation, but the use of each transportation mode is unaffected. Degree of hearing loss affects most questions regarding hearing in relation to driver abilities, while avoidance of specific traffic situations or environments is only associated with hearing loss in specific situations. Hearing loss has only minor effect on the factors causing inattention when driving and on the interest in a warning system for driver inattention. The general interest in a warning system for driver inattention is high.

Conclusions: Hearing loss influences the prevalence of driving license and criteria for choosing transportation, however has no effect on the frequency of any transportation mode. In general, in this study, respondents with profound hearing loss are less concerned, indicating that they might be coping. The interest in warning system for inattention and the attitude towards strengthening of auditory information in traffic situations is high regardless of hearing category. This suggests further research on coping strategies and on design of support systems accessible for drivers with hearing loss.

A simulator study of a critical frontal collision situation was conducted in order to examine usefulness of different warning modalities from a principal other vehicle (POV). In total, 48 participants drove 30 km while performing a secondary task, announced by a vibration in the seat, and experiencing light and/or sound warnings from oncoming traffic.

For comparison field measurements of light and horn sound levels were collected. The measurements were used for the implementations in the simulators graphics- and sound system respectively.

The study aims at providing basic understanding of driver responses to headlight and sound warning coming from another vehicle. A possible application is the implementation of systems for automatic activation of these warnings. Systems for automatic activation of brakes and steering are currently entering the market. These systems use proximity sensors to monitor the state of surrounding road users. Depending on the specific situation the effort/possibility to avoid or mitigate an accident may differ significantly between the principle road users of a pending collision, e.g. one road user (1) may easily avoid a collision while another (2) may not be able to do so. The only possibility for the second road user (2) to avoid a collision in such a situation is to issue a warning to the first (1), so that he/she may take evasive actions. Connecting the horn and the headlight to already existing sensor system, for automatic warning activation, is a cost effective means to provide such a warning. These types of warnings, could of course, also be triggered manually by the driver. The aim of this project is to evaluate the effectiveness of such a warning and also to validate if the warning between the road users is experienced as intended and whether the warning is an effective countermeasure for avoiding accidents.

There is limited research on how to design warning signals to avoid collision. In a simulator study auditory collision warnings with increasing intensity have been shown more effective than other types of auditory warnings (Gray, 2011). According to research regarding warning signals in general, auditory warnings should, if possible impart the nature of the events to the user. (Edworthy, 1995a). Research have also shown that people can match the frequency with which they respond to alarms to the false alarm rate, that increasing the perceived urgency of an alarm decreases reaction time and that increasing the number of modalities in which a warning is presented decreases reaction time. (Edworthy, 1995b)

Another objective of this study was to develop simulation technology for a realistic sensation of headlight glare and horn sound of an oncoming vehicle. The effect of using these signaling systems in a critical situation was then studied in the VTI simulator III (Nordmark, Jansson, Palmkvist, & Sehammar, 2004). The aim of the present study was to find a suitable warning signal, triggered by a first vehicle, which makes the driver of a second vehicle react fast enough to avoid a collision. It is important that the driver understands the message of the signal to be able to distinguish between “normal” horn and blink signals which are not time critical and this time critical warning. An additional cognitive task was used to distract the drivers to create a critical event.

The driving scenario was a rural road (70 kph speed limit) where the driver of a vehicle was distracted by means of a visual distraction task (reading and recalling letters from a screen placed at a relative large down angle (40-45 degrees), and then “pushed” across the median towards an oncoming vehicle, by introducing a steering angle in the simulated vehicle without submitting that information to the motion platform. The oncoming vehicle detects that the situation is critical and attempts to use headlight glare and horn sound to warn the driver of the vehicle that is drifting into oncoming traffic.

A within person design with four experimental warning conditions were used to evaluate the modality of the warning signals. Non critical noise and light signals from POV represented for example a greeting or a wish to make the driver aware of the headlight. The purpose of the non-critical signals was to evaluate if the driver understands the difference between the critical and non-critical signal. Measurements used to monitor driver behavior were lateral distance between the vehicles when passing, and driver reaction time (in term of steering wheel and brake pedal response). This was accompanied with subjective ratings during and after the test drive, both to evaluate the realism of the simulated event and the usefulness of the warning provided by the meeting vehicle.

The participants drove the Subject Vehicle (SV) with the instruction to drive as he or she usually does. In total, the participant experienced the critical event 5 times during this trip. Three different warning signals were presented, one at each event. The warning coming from the encountering vehicle was given through an automatic system triggering the horn and/or the lights of the POV. There was also a baseline event when no warning was given. The warning signals was presented in balanced order to avoid effects of which signal is presented first etc. The signal presented at the first event was also presented at the fifth event. This was to be able to investigate the learning effect. The non-critical noise and light signals were presented in the gaps between two warning signals.

The analysis is in process and will be completed in time for the full length paper submission. Preliminary results from the questionnaire show that participants have noticed the following warnings during the drive; sound (n=44), light (n=39), sound and light (n=32). Most participants think that the warnings were useful (n=31). Sound and vibration in the simulator is thought to be realistic. Participants are very positive to the announcement of the secondary task through a vibration in the seat. Most participants are positive to all three warning types; light (n=36), sound (n=31), light and sound (n=41).

Hörselintryckens betydelse för trafikanten är ett tämligen outforskat område. Studier som genomförts har främst handlat om exklusionskriterier för körkort och man har då kommit fram till att hörselskadade inte utgör en större risk än hörande bilförare. Således utgör inte hörselskada eller dövhet ett hinder för körkort. Det saknas dock forskning kring vilka risker individer utsätts för då hörselintrycken i trafiken helt eller delvis faller bort. Enligt SCB finns det 1.3 miljoner invånare i Sverige som har svårigheter att höra i en eller flera olika situationer. Den vanligaste typen av hörselnedsättning är åldersrelaterad. Ökad livslängd samt vanan att själv kunna transportera sig lätt, gör att vi får allt fler äldre bilförare och därmed även allt fler bilförare med nedsatt hörsel. En annan relevant aspekt handlar om den ökande andelen stödsystem i bilarna, vilka ofta använder sig av auditiva signaler (t.ex. varningar, GPS navigering). För maximal nytta av sådana system är det viktigt att de är tillgängliga för samtliga trafikantgrupper. Man bör därför undersöka möjligheten att använda sig av andra eller ytterligare signalmodaliteter, t.ex. ljus eller vibrationer. En ytterligare aspekt är att fordon blir allt tystare, vilket innebär att även trafikanter utan hörselnedsättning får mindre auditiv information eller feedback. Då kan det vara svårt att som oskyddad trafikant höra en bil som utgör en risk. Även oskyddade trafikanter med hörlurar kan gå miste om dylik information.

På VTI har ett doktorandprojekt inletts tillsammans med forskarskolan HEAD (HEaring And Deafness) vid LiU i syfte att utreda hörselintryckens betydelse för trafiksäkerheten. Projektet inleds med en kartläggning av transportvanor hos olika grupper av individer med hörselnedsättning i Sverige med hjälp av en webenkät som skickats ut under maj 2011. Vid analysen kommer en kategorisering i grupper att göras på basis av deras hörsel (Audiogram). Projektet genomförs i samverkan med Hörselskadades Riksförbund (HRF) som ställt sig positiva till den här forskningen och de har varit behjälpliga med att rekrytera deltagare. Enkäten kommer även att skickas till en kontrollgrupp av hörande individer. Undersökning har genom gått etisk prövning. Resultaten av studien kommer att presenteras på Transportforum 2012.

Research regarding importance of auditory information in traffic situations is limited and not very up to date. Studies performed in several countries around 1980 state that hearing disorders or deafness should not be an exclusion criterion for driver’s license, since individuals with hearing loss are not considered as an increased risk to traffic safety. Research made tend to answer the question if road users with hearing loss pose a higher risk than road users with normal hearing. Possible risks which road users with a hearing disorder are exposed to have not yet been investigated.

According to brief discussions with individuals with hearing loss, concerns include; signing while driving, trying to speech read passenger while driving, hearing emergency sirens, knowing the direction from which a sound is coming, hearing seatbelt warning or other warnings your car may give.

Hearing loss is often age related. With longer life length and increasing transport habits of older people, the proportion of older road users (and road users with hearing loss) increase. Furthermore, support systems in cars tend to use auditory signals for warnings, which make them less accessible for users with hearing disorders. Other modalities for warning signals (light or vibration) could be a solution.

Auditory information is an issue also for road users with normal hearing; cars tend to be more silent and could therefore be hard to notice for vulnerable road users, bicycle riders with music players more or less isolate themselves from surrounding impressions. This presentation invites to a discussion regarding traffic situations where auditory information is important and how support could be given if necessary.