Disentangling age–gender interactions associated with risks of fatal and non-fatal road traffic injuries in the Sultanate of Oman

Introduction

Globally, more than 1.2 million people die every year from road traffic injuries (RTIs), and between 20 and 50  million suffer non-fatal injuries and subsequent disability directly attributed to road traffic crashes.1 In 2013, RTIs are ranked the seventh leading cause of global disability-adjusted life years (DALYs) and leading cause of death for young people aged between 15 years and 30 years.2 It is estimated that each year about 5% of gross domestic product in low-income and middle-income countries (LMICs) are lost to fatal and serious RTIs.1 LMICs alone account for about 85% of road crash deaths and 90% of the DALYs.1

The countries in the Eastern Mediterranean region are an exception, which record a much higher death toll from road crashes than other world regions.1 RTIs are the leading cause of DALYs lost in three Gulf Cooperation Council (GCC) countries: Saudi Arabia, Sultanate of Oman and United Arab Emirates.2 3 Oman has the second highest death rate from road injuries within GCC.1 In Oman, the years of life lost attributed to RTIs have increased by twofold from 11.8% in 1990 to 21% in 2010,4 exerting significant burden on economy and healthcare resources. The increase in RTIs and associated mortality burden remain unprecedented since mid-1990s5 while sustaining economic growth, rapid urbanisation, road infrastructure and a steady increase in motor vehicle use.6 Between 1970 and 2015, the coverage of paved roads increased from 3 km to 31 071 km, whereas the number of registered motor vehicles increased from 1016 to 1 302 312 during the same period.6 7 The rapid increase in private motor vehicles in Oman is partly due to limited availability of public transport services, especially in the capital city of Muscat, which holds more than a third of the total population. The population in Oman has also doubled in the last two decades, particularly the expatriate population representing 46% of the total population.8

In 2016, 4721 road traffic crashes were registered in Oman, of which 3261 were injuries and 692 were deaths.7 About 44% of all crashes were due to vehicle collision mostly four wheelers, 24% collision with fixed objects, 17% overturn mostly attributed to speeding, 12% involved pedestrians and 3% of the crashes involved animals.7 Motorbikes and bicycles accounted for approximately 2.4% and 2.8%, respectively, of all road crashes.7 Among those had fatal outcomes, 28.5% were aged 16–25 years, 48% in the 26–50 years age range, mostly healthy, men and those driving the vehicle at the time of incident.7 The high burden of mortality and disability has considerable economic, social and healthcare implications for the left-behind families, as these victims are usually the primary breadwinners. Overspeeding, overtaking, driver fatigue and collision between vehicles in non-signalled intersections and roundabouts were reported as the main causes of crashes.9–11

Road crashes occur as a result of a complex combination of risk factors such as drivers’ behavioural and personal characteristics, time of the day, road geometry, vehicle, traffic, environmental and weather conditions.12–15 Personal and behavioural risk factors, for example, lack of driving experience, violation of traffic rules, carelessness, fatigue, sleepiness, psychological stress, driving under the influence of alcohol, harmful and sedative drugs and using mobile phones while driving exacerbate the risks and the extent of crash injuries.10 13–16

Age and gender are critical risk factors associated with road traffic crashes and severity of RTI outcomes.12 16 17 Young males are at higher risk of road traffic crashes and fatal outcomes than their female counterparts, mainly attributed to overspeeding, overtaking, aggressive attitudes, risky driving for fun and poor compliance of traffic rules and regulations.1 17 18 However, in terms of the propensity of road crashes per mile driven, females generally have a slightly higher risk than males.19 The exposure to road crashes also depends on the frequency of new driving licences issued each month.20

In Oman, the minimum legal age for holding a driving licence is 18 years for light vehicles and 21 years for heavy vehicles, although the traffic authorities can issue a licence at age 17 years under certain personal circumstances, for example, only if the driver is the sole breadwinner of the family and driving is an essential requirement for their employment.21 The share of male licence holders is disproportionately high.7 Overall, males are over-represented at all ages especially in the working ages.22 This is attributed to high volume of male migration particularly from South Asia, and recent data show that non-Omani male expatriates have outnumbered their Omani counterparts.22 Unlike Saudi Arabia, there is no gender discrimination for driving in Oman. Females represent about 20% of all driving licence holders and about 26% of the new licences issued in 2015.8 Female workforce in Oman has also increased significantly from 57 815 to 130 077 between 2006 and 2015.22

There is a growing body of peer-reviewed literature on trends and behavioural characteristics associated with RTIs in Oman.5 6 23–27 However, there is little systematic demographic analysis of how individual risk factors such as age and gender interact with each other and with other behavioural factors in determining RTI outcomes. We address this pertinent research gap by examining the underlying interactive effects of age and gender of road crash victims on the extent of severity of RTIs in Oman. We hypothesise that the risks of serious and fatal RTIs are the highest among young males than their older and female counterparts. Disentangling the age–gender interactions associated with RTIs will enable policy makers to identify and design appropriate behavioural interventions specific to certain high-risk groups.

Fatal road traffic crashes have become a routine public health emergency, and reducing the burden of RTIs is a national-level high priority policy agenda in Oman.28 Most of the hospital deaths due to external causes are attributed to road crashes,23 and increasingly a significant proportion of public and private funds is spent on managing, treating injuries and associated chronic physical and mental disorders.24 Identifying primary level risk reduction strategies are therefore highly critical in reducing the burden of mortality and morbidity associated with road injuries. The need for evidence-based policy interventions was highlighted in the 2015 WHO Global Status Report on Road Safety, which reiterated the plan of actions endorsed under the UN Decade of Action for Road Safety (2011–2020) declaration.1 In addition, the recently introduced United Nations Sustainable Development Goal 3.6 aimed at halving the global road traffic deaths and injuries by 2020.1

Methods

Results

The percentage distribution of severity of RTI outcomes by selected variables is presented in table 1. One in three of road crash victims had mild or moderate injury, and 1 in 10 had a fatal injury. Male drivers were twice as likely to cause fatal and severe injuries as females. The propensity for causing fatal injuries was the highest among males below 20 years and those aged 45–49 years. The propensity for severe injury was pronounced particularly among those aged below 20 years. The age–gender patterns associated with the severity of RTIs are illustrated graphically in figure 1. Most crashes were caused by young drivers aged between 20 years and 30 years, predominantly male drivers, whereas their females counterparts were mostly represented between ages 25 years and 30 years. Interestingly, a small minority of males involved in road injuries appeared to be driving illegally below age 18 years. There were only a few male drivers aged 60 years and above. Females were less likely to drive after age 40 years.

Overspeeding, fatigue and negligence were the three dominant causes of RTIs. However, the most common cause of fatal injuries was non-human factors (14.8%) and overspeeding (12.7%). Fatal injuries were common in crashes at both one-way and two-way roads, and in circumstances where a single vehicle was involved, bus and heavy vehicles such as lorry and trucks and during weekend and festive or holiday seasons (July–September). There was no uniform pattern of injuries across time. Note data for 2014 were incomplete and were available from 1 January to 2 November. Expatriate drivers from other Arab countries, Bangladesh and Pakistan, were at higher risk of fatal injuries. The variations in severe and fatal injuries were noticeable across governorates or regional headquarters. Wusta in the central region and Dhofar the southern and largest governorate recorded the worst in terms of fatal injuries. However, both severe and fatal injuries were the lowest in the most populous Muscat governorate.

Table 2 presents the coefficients and 95% CIs from the generalised ordered logit regression, controlling for primary and secondary predictors, and control variables. The probability of RTIs increased significantly towards severe and fatal outcomes for males, whereas female drivers had higher probability of being involved in the lowest threshold between mild and no injury. The age effects were marginally significant in most categories except for the below 20 years and 20–24 years age group. We interpret the results in table 2 in conjunction with adjusted conditional probabilities shown in table 3. The model-based conditional probabilities presented in table 3 clearly demonstrates evidence that the most dominant group at risk of all types of RTIs was young males. The probability of causing severe incapacitating injuries was the highest for drivers aged 25–29 (26.6%) years, whereas the probability of causing a fatal injury was the highest for those aged 20–24 (26.9%) years.

Overspeeding was the most dominant cause of crash for all types of RTIs, and it contributed relatively more to fatal injuries (67.1%). For example, the relative risk of fatal against no injuries was twice for overspeeding behaviour compared with that of fatigue and wrong manoeuvre, calculated as (67.1/14.3)/(52.0/22.6). For each of the other risk factor, the relative risk of fatal injuries was much heightened for crashes involving multiple vehicles, somewhat higher for crashes on one-way road, involving heavier vehicles (including bus and four wheelers), during July–December (festive, holiday and mild-winter season) and among Omani nationals.

Although the trends were not monotonic, the relative risk for fatal and severe injuries had increased from 2010 to 2014. The variations in RTIs were noticeable across governorates or regional headquarters: the severity of RTIs increased significantly in other governorates when compared with the most populous Muscat, particularly Wusta and Dhofar characterised by longer stretches of roads with higher speed limits and less traffic congestion. However, the relative risk of fatal injury against no injury was the highest in Muscat when compared with other governorates.

Finally, we examined the three-way interactions of risk factors: gender, age and cause of crash. Overspeeding featured as the leading cause of RTIs for most risk groups, especially among young males, followed by fatigue, wrong manoeuvre and negligence (table 4). For example, the proportion of fatal injuries among males that can be attributed to overspeeding ranged from 4%–6% for those aged below 20 years or above 34 years, to 13.4% for those aged 25–29 years and 17.7% for those aged 20–24 years. These were considerably higher than the other causes of crash for fatal injuries among males. Even for no injury crashes among males, overspeeding was the dominant cause across all age groups. There was no discernible pattern in the distribution of risk factors for female drivers. Nevertheless, overspeeding was also the dominant cause for fatal and severe injuries for females particularly in the 25–29 years age group.

Discussion

Road traffic crashes remain an unresolved global public health emergency in most LMICs. The risks of RTIs are considerably high in GCC countries including Oman where the oil-driven economy has overtime sparked rapid economic growth accompanied by large influx of expatriates, rapid urbanisation and unprecedented growth in motor vehicles. Our findings demonstrate evidence that the high burden of severe and fatal RTIs in Oman might be attributed to overspeed driving behaviour of particularly young males. The findings offer new insights to understanding the demographic influence of RTIs in Oman, where evidence-based interventions for road safety are critical to tackling the high burden of injuries.

The findings provide statistical evidence and confirm our research hypothesis that the odds of severe incapacitating and fatal injuries are significantly higher for young males than their older and female counterparts. In the event of causing a road crash with severe and fatal injuries, males aged 20–29 years represent the highest risk group. In comparison, females aged 25–29 years are more likely to be involved in mild and moderate injuries. Although fatal injuries are the highest among expatriate drivers from other Arab states, Bangladesh and Pakistan, the relative risk of fatal outcomes against no injury is much higher for Omani citizens. In geographic terms, fatal injuries are more likely in Wusta and Dhofar. The relative risk of fatal injury, however, is much higher in the most populous capital city of Muscat, which accommodates more than a third of total population in Oman.

Analysis of multiple risk factors demonstrates compelling evidence of overspeeding21 as the primary cause of fatal and severe injuries especially among young males, significantly more than the other causes. There is also evidence of negligence and fatigue in drivers experiencing severe and fatal injuries. Although drink driving is uncommon in Oman, our database show that about 2% of the drivers had alcohol while driving the vehicle. According to the 2016 data released by the ROP, 53% of all road crashes (n=4721) were attributed to overspeeding and 4% overtaking, 15% each attributed to fatigue and neglect and violation of traffic rules, respectively, 7% not keeping required safety distance, 4% driving vehicles with mechanical defects, 1% road defects and less than 1% attributed to sudden stopping and weather conditions.7 The high risk of fatal and severe injuries among young males exert considerable long-term impact on the left-behind families in terms of emotional, economic and social well-being. In addition, healthcare expenditure for managing disability and chronic conditions can be catastrophic for families and health systems in Oman. There is also an increase in female drivers in Oman, which highlights the need to initiate early gender-sensitive interventions targeting young male and female drivers. Equally important is to strengthen the provision and use of public transport systems across Oman that can have measurable impact in reducing both traffic flows and crashes and other lifestyle-related chronic and non-communicable diseases. Our findings have implications for road safety policies and interventions elsewhere in the middle-east region especially the other high-income countries within GCC.1 3

Most of the deaths, injuries and disabilities attributed to road traffic crashes are preventable with proper evidence-based legislative and policy interventions. However, the design and implementation of road safety interventions are often complex in a multicultural and heterogeneous society such as Oman where the current trends in road traffic crashes are dissuading, particularly in terms of achieving target 3.6 of the UN Sustainable Development Goals.1 About two-third of male population8 in Oman are below age 25 years, which highlights the dire need for comprehensive targeted policies and multisectoral interventions and strict legislation to tackle road safety. Institution-based (school, college and workplace) and family-based interventions could focus on promoting awareness about road safety and the implications of road traffic crashes; countermeasures such as routine traffic surveillance especially for heavy vehicles, harsh penalty and licence restrictions for young drivers could reduce RTIs.16 18 These interventions should also target the expatriate population, particularly new drivers from other LMICs who might not have adequate skills, knowledge about rules and regulations or driving experience in GCC countries.

The concerned authorities in Oman to whom our study recommendations apply include: the National Road Safety Committee established by the Royal Decree No.64/97 and headed by the Inspector General of Police and Customs and relevant members including the Directorate of Traffic, Ministries of Transport and Communication, Finance, Health, Housing, Social Development, Trade and Industry and Regional Municipalities.

It is important to highlight the data limitations of the present analysis. Unfortunately, we could not disentangle behavioural factors other than risky driving. Other useful information such as distance travelled, gender differences in the extent of overspeeding, driving experience, personal factors (eg, licence status, mobile phone use, stress, health conditions, previous incidents and type of profession) could help validate and improve our understanding of the risk behaviours. However, the present study could not explore these factors because of lack of data. Data on RTIs based on police judgement might be subject to bias and misclassification, although these records are verified by legal and insurance systems. For example, it is difficult to assess how fatigue and negligence are determined at the crash spot or later in the police investigations. Also, we could not analyse the influence of combination of risk factors such as overspeeding and negligence or drink driving because of lack of detailed (subjective) data. It is likely that some of the severe injuries could lead to fatal outcomes during or after hospitalisation, which could be potentially missed out in the ROP register. We could not explore the fatal and non-fatal injury outcomes of other passengers including children due to lack of data.

Despite these limitations, our study demonstrates systematic quantitative evidence of complex age–gender interactions associated with the severity of RTI outcomes. More importantly, the findings clearly pinpoint the importance and influence of age and gender in road crash analyses. It is recommended that future research should systematically address potential age–gender interactions in predicting risk behaviours associated with RTI outcomes.