Motor vehicle-related fatalities in South Africa increased from 11,157

in 1990 to 14,627 in 2009 (Road Traffic Management Corporation, 2009).

Driver error is said to account for 92.9% of motor vehicle crashes

(Treat et al., 1977).

These performance breakdowns are largely as a result of driver

distraction (Lee, 2006).

The growth of in-vehicle information systems (IVIS) is of concern, as

interacting with them while driving is a form of distraction (Alm & Nilsson, 1995).

THE EFFECT OF DISTRACTION MODALITY ON DRIVER PERFORMANCE

Tyron LOUW Department of Human Kinetics and Ergonomics

Corresponding address: Human Kinetics and Ergonomics Department Rhodes University P O Box 94 Grahamstown 6140 South Africa Email: tyronlouw@gmail.com Tel: 071 863 6730

INTRODUCTION

RESULTS

DISCUSSION & CONCLUSION

METHODOLOGY

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ECCENTRICITY (Degrees of Arc)

FUTURE RESEARCH DIRECTIONS

REFERENCES

Alm H and Nilsson L (1995). The effects of a mobile telephone task on driver behaviour in a car following situation. Accident Analysis and Prevention, 27(5), 707-715.

Lee JD (2007). Automation design. In G Salvendy (Ed.), Handbook of Human Factors and Ergonomics. Hoboken, NJ: Wiley.

Road Traffic Management Corporation (2009). Road Traffic Report 2009. Pretoria: Road Traffic Management Corporation.

Treat JR, Tumbas NS, McDonald ST, Shinar D, Hume RD, Mayer R E, et al. (1977). Tri-level study of the causes of traffic: Indiana University.

Figure 4: Overall mean tracking deviation between eccentricities, expressed as a percentage of baseline performance with an overlaid polynomial approximation (* denotes statistically significant difference, p<0.05).

There is a need to design IVISs such that their effect on driver

distraction is minimal.

Therefore, we need identify whether and to what extent the way in

which these are interacted with influences driving performance.

This requires quantification of the specific mental resources used by

each modality while driving.

From a mental resource perspective, there is limited and conflicting

research which simultaneously examines the effect of each modality on driver performance.

To quantify the effects of distraction modality on driver performance,

by analysing tracking performance in a driving simulator while attending to a secondary task.

This, in turn, allowed for an indirect measure of resource allocation

of the different modalities, and thus the identification of a preferable information modality for IVIS design.

CONCEPT

Dual task approach in low fidelity driving simulator TASK 1: ROAD TRACKING

The tracking task required participants to use the steering wheel of

the car to maintain the static yellow arrow on to the moving white line in the middle of a simulated road.

TASK 2: DISTRACTION

Participants were required to complete a comprehension task,

these were performed in three perceptual modalities, at two difficulties, over two consecutive trials each, which were then compared to pre and post control trials.

In order to compare the effects of modality the secondary tasks

contained information of the same nature.

Participants were required to answer comprehension questions

following each trial to ensure that they were maximally distracted. Task Priority:

Participants were instructed to devote resources necessary for

successful secondary task completion and the degree of intrusion of this task on performance of the road tracking task was examined, which are presented in Figure 3.

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Baseline Auditory Central Peripheral Low High Low High Low High

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Figure 3: Mean tracking deviation expressed as a percentage of the baseline drive for each condition (* denotes statistically significant difference, p<0.05).

Effect of Modality: F(2,22)=71.45, p<0.01

Tracking performance differed significantly across and between all

modalities. The modality which elicited the smallest decrement in tracking performance was the auditory modality, followed by the central visual modality, followed by the peripheral visual modality.

Difficulty did not have an effect on these results , which means that

the relationship between the modalities hold true for the range of difficulties as defined by this study.

Effect of Difficulty: F(1, 44)= 38.95, p<0.01

There was an overall significant decrement in tracking performance

between the low and high difficulty conditions. This trend was consistent intra-modally, except for the central visual modality where there was no difference.

Effect of Repetition: F(1, 22)= 4.53, p<0.01

There was a significant learning effect experienced overall for all

conditions. However, considered individually, there was not.

RESEARCH QUESTIONS

STATISTICAL ANALYSIS

1. Is driving performance during secondary task execution influenced by the modality in which the information is presented?

2. Is there any difference in driving performance with a change in

secondary task difficulty? 3. Is driving performance during secondary task execution influenced by the eccentricity at which the information is presented?

Relative to Pure Driving:

Attending to a secondary task, regardless of modality or difficulty,

significantly degrades tracking performance by a minimum of ~19%.

Effect of Eccentricity: F(2,44)=36.34, p<0.01

Tracking performance degraded significantly as the information

display for the secondary task increased in eccentricity.

6 conditions, 2 repetitions each.

Auditory low: Aurally with no noise overlaid.

Auditory high: Aurally with signal-to-noise difference of 10dB.

Central Visual low: 0° with no manipulation of text presentation.

Central Visual high: 0° with text character spacing decreased to 4pt.

Peripheral Visual low: Information presented at 10° eccentricities.

Peripheral Visual high: Information presented at 20° eccentricities.

24 Subjects (12 Males & 12 Females, 22±1 years old).

With regard to these findings, the peripheral visual field should be

avoided, due to the high demand of resources this channel requires, as seen in Figure 4.

The high difficulty secondary tasks should also be avoided where

possible, yet if necessary, the difficulty should be kept to a minimum.

It is essential that these findings are considered in the design of

IVIS, as the prevalence of IVISs will continue to rise.

If the IVISs which utilize similar conditions to those studied herein

continue to be designed and employed in motor vehicles, this will place strain on the central processing of both tasks which will increase crash risk due to driver distraction.

Driving performance attributed to a secondary task differed

significantly. Therefore, performing a secondary task whilst driving places additional strain on the perceptual and cognitive resources, in excess of that imposed by the driving task itself.

There are significant modal differences in driving performances,

with the auditory modality proving to affect driving performance to a lesser as compared to both visual modalities.

However, auditory tasks are force-paced, as opposed to visual

tasks which are self pace.

Recommendations therefore include the modality in which IVIS are

attended to by the driver and the extent to which the IVIS demands attention.

Horizon334 cm

Projection

screen

Tracking Point

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Figure 2: Geometric positions of driver and simulation display.

AIM OF STUDY

Figure 1: Driver’s view of driving simulator in the central visual low condition.

Statistical evaluation:

3-factorial ANOVA (Modality, Difficulty, Repetition).

Tukey’s Post-hoc analysis.

Dependant variable:

Performance index derived from tracking performance, with

reference to pure driving = 100%.

CONDITIONS & SUBJECTS

Effect of age on resource allocation in different modalities.

Future analysis could focus on the responses of the modalities

used in this study when the information attended to in the secondary task is relevant to the driving task.

Given the increasing prevalence of HUDs, future research could

focus on the resource functions within the central visual field, the 0° to 10° range.

Future studies could examine whether and in which modalities

distractions may be used in a positive way to combat the effect of fatigue and monotony while driving.