Human Factors as Causes for Road Traffic Accidents

205 Pages·2013·4.88 MB·English

Human Factors as Causes for Road Traffic Accidents in the Sultanate
of Oman under Consideration of Road Construction Designs

Inauguraldissertation zur Erlangung des Doktorgrades (Dr. phil.) der philosophischen Fakultät II
(Psychologie, Pädagogik und Sportwissenschaft) der Universität Regensburg

Vorgelegt von
Kai Plankermann
Burglengenfeld
2013
Erster Gutachter: Prof. Dr. phil. Dr. h.c. Alf Zimmer
Engineering Psychology Unit, University of Regensburg

Zweiter Gutachter: Prof. Dr. rer. nat. Mark W. Greenlee
Institute of experimental Psychology, University of Regensburg
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Acknowledgement

I would like to express my deepest gratitude to my advisor Professor Alf Zimmer for accepting me as
his PhD student and for providing me with his continuous support. I would also like to thank Dr.
Abdullah Al-Maniri who supported me throughout the data collection in Oman. Also, I owe my
gratitude to Aisha Al-Belushia who conducted the interviews at Ibra Hospital. Finally, I would like to
thank the following persons for contributing to this thesis in one way or another and apologize to
those I forgot to mention.
The Engineers Altayeb Al-Harthi, Muhammad Al-Hosny (both Muscat Municipality) and Saleh Al-
Shukaili (Directorate General for Road and Land Transportation) for providing the road data; the Drs.
Muhamad Zaheerudeen (Khoula Hospital), Salem Al-Abri (Nizwa Hospital) and Ali Al-Dawi (Ibra
Hospital) for facilitating the data collection at the hospitals; the Engineers Jochen Zimmermann (IJK
Associates), Jens Aalund, Klaus Andersen (both COWI) and Jürgen Piel (STRABAG) for fruitful
discussions about road safety in Oman; Muhamad Al-Aamri, Mahmud Al-Khatri, Yousuf Al-Rawahi
and Mazin Al-Wahibi for helping me during the data collection; Chantal Blake and Amanda Amarotico
for proofreading first drafts of this thesis; Dr. Montasser Abdelghani for translating the German
questionnaire into Arabic; my Nissan X-Terra for being a reliable and most importantly safe
companion while travelling the ten thousand kilometers through Oman to collect the data for this
thesis; and, last but not least, I would like to thank my wife Marlene and my daughter Lina for their
patience as well as my parents for their support.

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“Academic work needs to follow rules of good practice, but we should not confuse rigor with
tediousness or objectivity with lack of personality. Academics are still ‘human after all’ – to quote
Daft Punk. And beyond the barren scientific facts that academics produce, they have a life, an
upbringing, a cultural context they inhabit, with opinions and passions (Hassenzahl, 2010).”

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Table of contents

Executive summary ................................................................................................................................. 8
Part I: Introduction ................................................................................................................................ 10
1. The global burden of RTAs............................................................................................................ 10
2. RTAs in Oman ............................................................................................................................... 10
3. RTA research ................................................................................................................................. 11
3.1 The system approach ............................................................................................................... 12
3.2 Education, enforcement and engineering ................................................................................ 13
4. Objectives and structure .............................................................................................................. 14
Part II: Theory and literature review ..................................................................................................... 18
1. The human factor ......................................................................................................................... 18
1.1 The driving task ........................................................................................................................ 18
1.2 Driving and attention ................................................................................................................ 20
1.2.1 Mental overload ................................................................................................................... 20
1.2.2 Mental underload ................................................................................................................. 22
1.3 Driving and perception ............................................................................................................. 23
1.3.1 Speed perception ................................................................................................................. 23
1.3.2 Time to collision .................................................................................................................... 25
1.3.3 The Useful field of view (UFOV) ........................................................................................... 26
1.3.4 Where do drivers look and what do they see? .................................................................... 27
1.4 Information processing............................................................................................................. 31
1.4.1 Bottom-up and top-down processing .................................................................................. 31
1.4.2 Situation awareness and schemata ...................................................................................... 32
1.5 Driver behavior models ............................................................................................................ 36
1.5.1 Risk threshold models .......................................................................................................... 36
1.5.2 Compensation models .......................................................................................................... 37
1.5.3 Risk avoidance models ......................................................................................................... 38
2. Road design .................................................................................................................................. 39
2.1 The driving task and the road design ....................................................................................... 39
2.2 Road categorization .................................................................................................................. 41
2.3 The self-explaining road (SER) .................................................................................................. 42
2.4 The forgiving road..................................................................................................................... 46
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2.5 Design elements ....................................................................................................................... 47
2.5.1 Design and posted speed ..................................................................................................... 47
2.5.2 Sight distance ....................................................................................................................... 51
2.5.3 Road signs ............................................................................................................................. 55
2.5.4 Road markings ...................................................................................................................... 59
2.6 Road location elements ............................................................................................................ 61
2.6.1 Transitions ............................................................................................................................ 61
2.6.2 Intersections ......................................................................................................................... 69
2.6.3 Horizontal curves .................................................................................................................. 73
2.6.4 Straight sections ................................................................................................................... 76
2.6.5 Roundabouts ........................................................................................................................ 80
Part III: Human factors .......................................................................................................................... 83
1. Methods ....................................................................................................................................... 83
1.1 Data collection .......................................................................................................................... 83
1.1.1 Ethical approval .................................................................................................................... 83
1.1.2 Participants and selection criteria ........................................................................................ 83
1.1.3 Location and period of data collection ................................................................................. 84
1.1.4 The questionnaire based interview ...................................................................................... 85
1.1.5 Data handling........................................................................................................................ 87
1.2 Data analysis ............................................................................................................................. 87
2. Results .......................................................................................................................................... 88
2.1 General results ......................................................................................................................... 88
2.1.1 RTAs per months .................................................................................................................. 88
2.1.2 Road users ............................................................................................................................ 89
2.1.3 Nationalities .......................................................................................................................... 90
2.2 RTA types .................................................................................................................................. 91
2.3 Technical factors ....................................................................................................................... 92
2.4 Bivariate analysis ...................................................................................................................... 93
2.4.1 Common factors ................................................................................................................... 93
2.4.1.1 Age ......................................................................................................................................... 94
2.4.1.2 Intoxication ............................................................................................................................ 95
2.4.1.3 Inappropriate speed .............................................................................................................. 96
2.4.1.4 Insufficient safety distance .................................................................................................... 98
2.4.1.5 Driving experience ................................................................................................................. 98
2.4.2 Perception .......................................................................................................................... 101
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2.4.2.1 Visibility ............................................................................................................................... 101
2.4.2.2 Obstructed view .................................................................................................................. 103
2.4.2.3 Unintended blindness ......................................................................................................... 103
2.4.3 Attention............................................................................................................................. 104
2.4.3.1 Fatigue ................................................................................................................................. 104
2.4.3.2 Distraction by technical device............................................................................................ 105
2.4.3.3 Distraction by non-technical device .................................................................................... 106
2.4.3.4 Conversation........................................................................................................................ 107
2.4.3.5 Emotions .............................................................................................................................. 108
2.4.4 Cognition ............................................................................................................................ 109
2.4.4.1 Self-assessment of driving skills .......................................................................................... 109
2.4.4.2 Safety of own car ................................................................................................................. 109
2.4.4.3 Route familiarity .................................................................................................................. 110
2.4.4.4 Dangerous driving ............................................................................................................... 111
2.4.4.5 Impatience ........................................................................................................................... 111
2.4.4.6 RTA history .......................................................................................................................... 112
2.5 Multivariate analysis............................................................................................................... 112
2.5 Main human factors and RTA types ....................................................................................... 114
Part IV: Human road interaction ......................................................................................................... 115
1. Methods ..................................................................................................................................... 115
1.1. Data collection ........................................................................................................................ 115
1.1.2 Interview data and evaluation of RTA scene ...................................................................... 115
1.1.3 Muscat Municipality and Directorate General of Road and Land Transport data ............. 116
1.1.4 Complementing missing data ............................................................................................. 116
1.1.4.1 Curves .................................................................................................................................. 117
1.1.4.2 Intersections ........................................................................................................................ 117
1.1.4.3 Roundabouts ....................................................................................................................... 118
1.1.4.4 Roadside development (urban and rural roads) ................................................................. 120
1.2 Data analysis ........................................................................................................................... 121
1.3 Confounding and interaction.................................................................................................. 125
2. Results ........................................................................................................................................ 125
2.1 Specific objective one ............................................................................................................. 125
2.2 Specific objective two ............................................................................................................. 129
2.3 Specific objective three .......................................................................................................... 130
2.3.1 Self-reported speed on straight sections ........................................................................... 130
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2.3.2 Self-reported speed on T-intersections and curves ........................................................... 133
2.4 Specific objective four ............................................................................................................. 133
2.4.1 Straight sections ................................................................................................................. 135
2.4.1.1 Straight sections and fatigue ............................................................................................... 135
2.4.1.2 Straight sections and speed ................................................................................................ 136
2.4.1.3 Straight sections and conversations .................................................................................... 138
2.4.2 T-intersections .................................................................................................................... 139
2.4.2.1 T-intersection and unintended blindness ........................................................................... 139
2.4.3 Curves ................................................................................................................................. 140
2.4.3.1 Curves and speed ................................................................................................................ 140
2.4.4 Roundabouts ...................................................................................................................... 142
Part V: Discussion and recommendations ........................................................................................... 144
1. General discussion ...................................................................................................................... 144
2. Design recommendations ........................................................................................................... 150
2.1 Applying basic design standards on road design .................................................................... 150
2.2 Considering dual carriageways and overtaking lanes ............................................................ 151
2.3 Capturing the road users’ attention is insufficient for safe transitions ................................. 153
2.4 Reducing speed and restricting affordances at T-intersections ............................................. 154
2.5 Improving visual guidance in curves ....................................................................................... 155
2.6 Marking roundabouts according to different categories ....................................................... 156
3. Behavioral adaptations and safety audits .................................................................................. 157
4. Limitations .................................................................................................................................. 159
4.1 Interview data......................................................................................................................... 159
4.2 Road data ................................................................................................................................ 160
4.3 Culpability analysis ................................................................................................................. 160
4.4 The effect of adjacent road location elements ...................................................................... 160
5. Concluding remarks .................................................................................................................... 161
Appendix A .......................................................................................................................................... 162
Appendix B .......................................................................................................................................... 170
Appendix C........................................................................................................................................... 179
Appendix D .......................................................................................................................................... 188
References ........................................................................................................................................... 190

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Executive summary

The Sultanate of Oman has one of the highest road traffic accident (RTA) related fatality rates
worldwide (Al Lamki, 2010). Since Sultan Qaboos addressed this issue in a speech in October 2009,
research institutions, ministries and NGOs alike have strengthened their efforts to cope with this
public health burden. Yet, still little is known about the factors contributing to the high number of
RTAs.
Evidence from research conducted in other countries suggests that the human factor and the
interaction between the human factor and the road environment are among the most frequent
contributors to the occurrence of RTAs. The ultimate goal of this thesis was therefore to provide
recommendations on how to adjust the road design to the human factor. In order to meet this goal,
two objectives were determined, namely to identify the main human factors that contribute to the
occurrence of RTAs in Oman and to investigate the human road interaction as a contributing factor to
the occurrence of RTAs in Oman.
A total of 296 in-depth interviews were conducted in three Omani hospitals with road users who
were involved in RTAs. The data collection took place between April 2011 and May 2012. Road and
environmental information were collected by visiting the RTA locations and using Google earth. In
addition, road data for each RTA location was requested and provided from Muscat Municipality and
the Directorate General of Road and Land Transport.
For the first objective, identification of the main human factors that contribute to the occurrence of
RTAs in Oman, the study on human factors conducted by Gründl (2005) was replicated. The results
revealed five human factors that significantly increase the risk of causing an RTA in Oman. These
factors are according to the strength of their impact: (1) inappropriate speed, (2) fatigue, (3)
unintended blindness, (4) annual mileage between 20.000 and 40.000 km and (5) having a
conversation with the passenger.
The second objective, investigation of the human road interaction as a contributing factor to the
occurrence of RTAs in Oman, was split into four specific objectives. These objectives addressed the
extent to which roads in Oman can be considered self-explaining, the subjective perceived safety of
roads, road design elements that affect driving speed and the prevalence of selected human factors
according to road design elements.
For the first specific objective, the extent to which the Omani road design corresponds to the
recommendation on self-explaining roads suggested by Matena (2006) was investigated. It was found
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that none of three recommendations are met and concluded that this discrepancy may add to the
occurrence of the human factor inappropriate speed.
For the second specific objective, a logistic regression analysis was calculated with the dependent
variable subjectively perceived safety of a road and various design elements as independent
variables. The results indicate that the number of carriageways is the only design element that
predicts subjectively perceived safety of a road.
For the third specific objective, correlations and linear regression models were calculated with self-
reported speed as a dependent variable and various road design elements as independent variables.
It was found that speed is significantly higher in rural environments. The effects of lane and shoulder
width on speed differ between rural and urban environments. Interestingly, driving speed did not
correlate with the number of carriageways.
For the fourth specific objective, the prevalence of human factors according to various design
elements was investigated using logistic regression models. Among others, the regression models
revealed that the human factor fatigue occurs more frequently on roads with dual carriageway and
that inappropriate speed occurs more frequently on curves without warning signs. Contrary to
previous studies (Werneke & Vollrath, 2012), it was found that the human factor unintended
blindness occurs more frequently at T-intersections characterized with a high traffic volume than at
T-intersections with a low traffic volume.
Based on a discussion of the findings, the suggested recommendations focus on the following
aspects:
 Applying basic design standards on road design.
 Considering dual carriageways and overtaking lanes.
 Capturing the road users’ attention is insufficient for safe transitions.
 Reducing speed and restricting affordances at T-intersections.
 Improving visual guidance in curves.
 Marking roundabouts according to different categories.
This thesis is the first scientific work that has investigated the role of human factors and their
interaction with the road environment in the causation of RTAs in a Gulf country. Although specific
recommendations are suggested, this thesis is to be considered a source for future research rather
than a design guideline
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