In contemporary times, arguably one of the most stressful outdoor jobs is truck driving [1-6]. Empirical evidence and verifiable statistics suggested that truckers who are engaged in freight distribution have one of the highest career turnover rates globally [1, 3-5]. A 2017 statistics from the American Trucking Association (ATA) observed that the United States industry experienced a staggering 90% job turnover rate among truckers in 2016 [6, 7]. The causative factors behind such a high rate of job turnover are heavily linked to the job schedule of an average trucker [1, 3, 6]. Different studies have established the fact that due to high occupational stress, limited access to health care services and prolonged absence from loved ones; there are disproportionally high incidences of occupational health-induced conditions among truckers when compared to other similar outdoor careers [8-10]. Truckers are discovered to be particularly exposed to negative health conditions such as mental health breakdowns and ergonomically hazardous working conditions [8, 10]. It is therefore not surprising that incidences of Substance Use Disorder (SUD) have been rampantly reported among truckers globally [1, 3, 4, 6, 7]. According to Sieber [11], high incidences of SUD occur among truckers who generally utilize different psychoactive substances and opioids to ameliorate perceived shortcomings in their physical conditioning. The reliance of some truckers on these substances as ‘quick fixes’ against different health challenges like fatigue, sleeping disorder, sitting/low back pain, musculoskeletal disorders and whole-body vibration has always put a disturbing question mark on their judgments when behind the wheels [3, 12, 13].

There has been a surge of interests among the academic communities in recent times on the apparent relationship between the Socio-economic Situation (SES) of Road Traffic Crashes victims’ and the possibilities of their involvement in Road Traffic Crashes (RTC) [14-16]. Most of these studies established the existence of strong concatenation between SES of RTC victims and the spatial pattern of RTC occurrence among different neighbourhoods in most urban locations

[14-16]. Some of the studies also provided insight into how various attributes of SES (particularly age, income, gender, ethnicity/cultural belief) play important roles in the possibility of one becoming an RTC victim in a particular location [16, 17]. A major premise ascertained from the findings of these studies is that the SES of an individual has an inherent proclivity for predicting the chances of his being involved in RTC across space and time in a studied location [16, 18, 19]. It is however perceptible that studies that examined the influence of SES on drivers' general involvement are rare. Contextual analysis of some of the studies [16, 17, 20] on the discourse revealed that some of the popular perceptions of the discourse are anecdotally obtained. Many of the aforementioned studies failed to establish a scientific premise on the existence of interface between the occurrences of RTC and SES of passengers, pedestrians and drivers [14]. While it might be true that drivers could sometimes be victims of RTC, there are empirical pieces of evidence which support the position that they are more of a causative factor in the occurrence of RTC [8, 21, 22]. This study therefore attempted to systemically consider how key attributes of SES (age, gender, educational attainment, marital status and period spent in employment) and the existence of SUD, influences adherence to safety rules guiding the conveyance of liquid petroleum products by truckers. The available literature is replete with studies that focused on how the attributes of SES influence the occurrence of RTC among different road users (pedestrians and passengers) [16, 18, 19]. It is also a fact in the literature that key SES attributes of age, marital status educational attainment and the working condition affect drivers' disposition towards SUD, which in turn influences their abilities to adhere to stipulated driving rules on roads [1, 3, 11, 12]. However, there is a paucity of evidence in studies that focused on how the attributes of SES among homogeneous professional groups like the truckers influence their attitudes to SUD and safety practices guiding the conveyance of hazardous goods like petroleum products.

For the purpose of this research, a positivist approach is considered as being the most ideal. The study was carried out in Ibadan metropolis in Nigeria between June 2017 and December 2018. The studied population comprised of 632 members of the Petroleum Tanker Driver Associations (PTDA) Ibadan zone servicing 702 Fuel Retail Outlets [FRO] within the metropolis at the time of the research. The research protocol was approved by the ethical committees of the University of Fort Hare (South Africa) and Redeemer’s University (Nigeria). All participants were duly notified of the aim of the research. Then, informed consent was obtained from the participants. In accordance with the dictate of the ethical protocol, the reassurance of confidentiality of all the participants in the study was confirmed. All sourced data were documented by code, rather than the respondent’s name. A multistage sampling technique was employed in selecting respondents for the study. Available records from the register of Petroleum Tanker Drivers Association showed that there are 632 registered members of the group servicing FRO in Ibadan and environs. A simple random sampling technique was employed in selecting respondents for the study. Information garnered from the register of the Petroleum Tanker Drivers Association (PTDA) Ibadan branch revealed that all the 632 registered truckers are also affiliated to the 702 Fuel Retail Outlets (FRO) in the metropolis. The research team used the register in selecting every odd-numbered member on the list as a potential respondent for the research exercise. Since the address of the FRO they serviced are on the register, the research team linked up the two and thereafter visited each of such FRO and attempt was made to sample such trucker. A total number of 351 respondents were sampled from which 265 questionnaires were retrieved for this analysis (a response rate of 75.49%). The study utilized a self-reporting approach in obtaining information about the incidences of SUD among different categories of drivers [22-26]. According to Girotto et al. [25], the use of the self-reportage technique in analyzing issues surrounding SUD among truckers could provide deeper introspective knowledge than biological analyses. Biological analyses while being adept at identifying the presence of alcohol and other substances could only be useful if the consumption of such substances is done hours or a few days prior to sample collection. The biological analytical approach most often than not also underestimates the intake prevalence and level of addiction. The self-reportage technique is also not without its own demerits as respondents could sometimes withhold information deliberately due to fear of losing their driving licenses or sometimes as a result of outright forgetfulness of information. Structured questionnaires with three different sections were used in obtaining the required information from respondents; the questionnaire which was divided into three sections had Section A that obtained information on the Social Economic Situation (SES) of the respondents. Section B which employed a Likert scale (where responses were categorized into four options of strongly disagreed, disagreed, agreed and strongly agreed) was used to get the necessary information on respondents' attitude/disposition to SUD. The third section which extracted information on the willingness of respondents to comply with Health Safety Environment (HSE) stipulations guiding the conveyance of petroleum products was measured through the development of dichotomous measurable operational definitions which provided a yes or no response to the question. A pre-field exercise helped in ensuring the validity and reliability of the research instruments. Additionally, the Cronbach alpha test was done on each of the constructed multi-items’ instruments in order to observe their internal reliability and ability to effectively measure the research variables [27]. The compliance to HSE stipulations subscale which consisted of 8 items has a Cronbach alpha of .79 (α=.79) while attitude to SUD subscale which had 9 items has a Cronbach’s alpha of .80 (α=.80). The information retrieved from the questionnaires was codified into Microsoft Excel (2010) workbook sheet where the database management was done thereby getting the data into good shape for the analysis. The statistical analyses were performed using IBM SPSS (Statistical Package for Social Sciences), version 23. Bivariate analysis done through chi-square was employed to test for the possibility of the existence of relationships/associations between three SES variables (age, literacy level and numbers of years spent in marriage) of truckers and incidences of SUD. Furthermore, the Logistic Regression Logistic Regression Model (LRM) was used to test the existence of significant relationships between the dichotomous dependent variable (compliance to HSE stipulations guiding the conveyance of petroleum products) and the different independent explanatory variables (Age, Marital Status, Educational Status and Substance Use Disorder). Logistic Regression as a classification algorithm is ideal for predicting a binary outcome (yes or no) given a set of independent variables.

On the strength of the application of both the sampling frame and sampling size techniques as conceptualized above, 265 (75.49%) out of the 351 distributed questionnaires were retrieved and used in the analysis to achieve the aim of this research exercise. Below are the analyses:

Some salient facts are established in this study. First is the scientific evidence of a strong association between some SES variables and incidences of SUD among truckers. Findings from different studies also corroborated this [23, 25, 36] for example, Williamson [23] discovered that younger and less experienced truckers are most likely to engage in SUD in order to reduce the stress associated with their work schedules. Alcanlz et al. [36] found out that younger truckers who are males are more likely to engage in SUD. However, most studies did not consider the effects (if any) of SES variables of marital status and years of formal education received on attitudinal reaction to SUD. Findings from this study affirmed therefore that literacy is a key determinant of truckers’ perception on SUD (Table 2). While some studies have established the existence of a strong association between some SES variables, pure economic factors (payment by results/quicker delivery time), Job Satisfaction Level (JSL), and SUD among truckers [23, 36, 37] the role played by a seemingly innocuous factor like numbers of years of schooling a trucker got has largely been overlooked. The study also showed that the marital status of truckers is not a significant factor that influences attitudinal disposition towards SUD (Table 2).

Another reality that this research brought to the fore is the possibility of predicting truckers compliance to HSE stipulations guiding the conveyance of petroleum products based on some of their SES variables and their attitudinal dispositions to SUD (Table 3). Perhaps explanatory research on a larger scale (regional or national) on the subject could reveal the existence of causality between the identified independent variables and compliance to HSE stipulations guiding the carriage of petroleum products among truckers. Already findings have shown that there are existences of causalities between economic factors (better pay packages) and compliance to HSE stipulations among truckers [23, 36, 37] Results from this research further posited that among Nigerian truckers, critical SES variables which are not necessarily economic in nature have a strong influence on their compliance to HSE stipulations guiding conveyance of petroleum products. Result of the statistical analysis (Appendix Table 2) showed that marital status, educational status and attitude towards SUD, all significantly predicted compliance to HSE stipulations guiding the conveyance of petroleum products. It was only age that did not significantly predict compliance to HSE stipulations guiding the conveyance of petroleum products in the metropolis.

The likelihood of the existence of interrelationships between SES variables of years of formal education received by truckers, marital statuses, the effect of such variables on their attitudinal disposition to SUD and the impact of the three on compliance to HSE rules guiding petroleum products conveyance as suggested by this study could help in future policy formulation on the discourse. Trucking organizations should be encouraged to recruit young drivers who are relatively more literate; findings from different researches strongly suggested the existence of an association between health literacy and reduction in the risk associated with SUD among adolescents [24, 38]. UNODC [24] particularly discovered that adolescents who have greater “academic competence” are less likely to be involved in SUD (Pg 15). While marital status was not a significant predictor of SUD among the respondents, it is observed that there is a general reduction in incidences of SUD as years spent in matrimony increase (Table 2). This result corroborated findings from other studies which suggested that marital status among drivers does not influence SUD and RTC outcomes [39-42].

This research undertook the filling of a critical gap in the body of extant literature by examining the relationships between key SES variables (age, educational status, and marital status) and their effects on attitudinal disposition towards SUD among truckers. The study also contributed by revealing that key SES variables and attitudinal disposition towards SUD significantly predicted compliance to HSE stipulations guiding the conveyance of petroleum products. Regardless of the important findings, this study has some limitations. An attempt was not made to adjust for the possibility of the existence of a collinear relationship among some of the multivariate factors in the model, particularly the likelihood of an existence of a collinear relationship between marital status, respondents' age and work conditions. Findings from some studies suggest the existence of a collinear relationship between work conditions and marital status among truckers [36, 37]. Another possible limitation could be in making a sweeping generalization based on findings from this study. The majority of the respondents who participated in the study are from the south-western part of Nigeria, there are therefore the possibilities of some peculiar cultural factors influencing their world views or beliefs as represented by their responses on issues surrounding SUD and compliances to HSE conditions guiding petroleum products conveyance in Ibadan metropolis.

Amongst other propositions on how to reduce the incidences of SUD among truckers, a 2016 World Health Organization report advocates a multifaceted approach which covers five essential areas of legislation, testing, enforcement, awareness-raising, counseling and treatment to address the malaise by different countries. According to the WHO [26], such an approach when sustained would bring much-desired change to the entire narratives of SUD among truckers and considerably reduce the global incidences of RTC.