Socio-economic Determinants of Intra-urban Trips Generation in Ogun State, Nigeria

The focus of this study is on the significance of Socio-economic characteristics of residents on intraurban travel in Ogun State, Nigeria. 1507 households were randomly sampled across the 14 urban centres in the state and information on intra-urban trip generation and 12 socio-economic variables in respect of them were collected. The multiple regression technique was used to establish the influence of socio-economic variables on intra-urban trip generated by households. The number of significant socio-economic determinants of intra-urban trips ranges between 2 and 8, while the proportion of the criterion (trip generation) explained by the predictors (socio-economic variables) ranges between 35.80 an 81.70% across the urban centers. The more developed urban centers have higher number of socio-economic determinants of trip than the less developed ones. On the other hand, the magnitude of criterion explained by the socio-economic variables is higher on the less developed urban centres. At regional setting, 8 out of 12 socio-economic variables namely: Number of workers, Age, Mode of travel, Sex, Occupation, Length of stay, Rent and Income significantly explained 46.10% of variation in criterion. This suggests the need to include variables on socio-economic development of cities in future research on intra-urban travel.


INTRODUCTION
Cities all over the world are characterized by a set of activities, which actually account for the concentration of people in them. Such activities are distinctively urban and include those arising from manufacturing, trading and finance, transportation and tertiary activities. All these combine to generate the spatial configuration of the city because their requirements are sometimes functionally differentiated and also spatially segregated. The spatial segregation of urban land use types creates spatial imbalance and this necessitates spatial interaction for functional interrelationships.
The urban centre of today is complex in nature, covers large expanse of land and accommodates varied activities (Hoyle and Knowles, 1998;Aderamo, 2004;Osoba, 2011;Raji, 2013). An outcome of this is that urban centre generates and attracts very large number of person trips daily.
Intra-urban travel represents an expression of an individual's behavior and as such it has the characteristics of being habitual. As a habit, it tends to be repetitive and the repetition occurs in definite pattern (Bruton, 1975). Studies (Ayeni, 1974;Adeniyi, 1981;Ojo, 1990;Ogunsanya, 2002;Solanke, 2005;Osoba, 2011;Badejo, 2011;Raji, 2013) have shown that in general, people tend to travel in order to obtain access to a variety of other peoples' services and facilities that are not available at the origins of their journeys.
In urban travel studies, evidences really abound supporting the effects of households characteristics on travel behavior. However in the previous works, emphasis is concentrated on one city at a time, thereby concealing the much desired variation in the phenomenon between cities. In other words, while the effects of socio-economic characteristics of people in urban travels are fairly well known at individual city level, the phenomenon is yet to be well established at regional setting especially in developing world.
The focus of this study therefore is on the significance of socio-economic characteristics of residents on intra-urban travel both at individual city level and regional setting in Ogun state of Nigeria.

LITERATURE REVIEW
Travel pattern studies within the urban centres have long attracted the attention of researchers in the field of travel behavior. Since the early 1970's, researchers have shifted their focus away from the traditional studies of purpose and modes of intra-urban travel to those that can adequately capture the processes underlying observed travel patterns in the light of the existing technology and contemporary planning process. Thus, studies since this period have been concerned with explaining how and why individuals distribute their trips from one or more given origin points.
The early works of Kansky (1967), Harton and Hultquists (1971) and Oppehoum (1975) on travel behavior employed multiple measures of travel pattern although none of these systematically related the travel pattern to personal attributes of the traveler. Perhaps the shortcomings of the earlier works prompted researchers like Hanson and Hanson (1981) and Oyesiku (1990) to devote more attention to the relationship between socioeconomic and demographic characteristics of residents within the urban centres.
Households with more than one motor vehicle tend to generate more trips per unit than households with only one motor vehicle; the occupation of head of the household is seen as one of the major indicators of the standard of living enjoyed by the family and reflects to a certain extent the family income. The ability to pay for a journey affects the number of trips generated by a household. Families with a high income can generally afford to satisfy more of their movement demands than low-income families. As one would expect therefore, increasing family income leads to greater trip production.
Family income is also said to be related to levels of motor vehicle ownership. A general conclusion from the above is that the travelers social and economic status can impose constraints on him/her within the urban area. Goeverden and Hilbers (2001) noted that personal characteristics of the traveler influence his demands upon quality and his willingness to pay. In the same manner, it has been established that households with higher income make more trips and travel greater distance (Ayeni, 1974). Also according to Kansky (1967) and Doubleday (1977), auto owners and the non-educated people make more trips than non-owners and the more educated when all trips are considered. Olayemi (1977) observed that apart from variation in both time and space, various socio-economic factors combine to determine why, where, when and how of movements in metropolitan Lagos, Nigeria. In a similar perspective, Ogunjumo (1986) using the regression analysis observed that the trip frequencies in Ife, Nigeria are affected by household size, number of workers per household and vehicle ownership. Just like Olayemi (1977) the study could not reveal the variation across cities because of its focus on a single urban centre.
In a nutshell from the above, the significance of socio-economic characteristics of respondents in intraurban travel cannot be overemphasized. However, concentration of previous works on one city at a time concealed the much-desired variation between cities and thus constitutes a gap in knowledge of urban travel studies. Attempt in this article is to contribute towards an existing gap in knowledge of urban travel by establishing the influence of socio-economic characteristics of urban residents on intra-urban travels at a regional setting choosing Ogun State of Nigeria as a case study.

METHODOLOGY
This study is on socio-economic characteristics of residents and trips generated within urban centres. An urban centre is defined as the settlement with a total population of 20,000 people or more in conformity with the United Nations and the definition of urban centre in the Nigeria National Population Census of 1963 and 1991. Based on this definition, there are 22 urban centres in the state. 14 of these in different categories (such as large, medium and small) of urban centres in terms of population sizes were randomly selected. They are: Abeokuta, (the state capital), Ijebu-Ode, Sagamu, Ilaro, Ago-Iwoye, Ota, Ijebu-Igbo, Ayetoro, Ifo, Iperu, Ado-Odo, Idi-Iroko, Owode-Yewa and Alagbado.
A household survey was conducted in each of these urban centres to generate data for this study. Towards the survey, each urban centre was divided into residential quarters along the demarcation of the town into residential neighborhoods by the zonal Town Planning Authorities (ZTPA). In each of the neighborhoods, random selection of streets and systematic sampling of the housing unit were made. The size of the household sample interviewed was based on the estimates for each urban centre. There were about 269,095 households in all the selected urban centers out of which 1,507 were sampled in proportion to the number of households in each city (Table 1). 1,300 fully completed copies of the questionnaire were used in this study. The questionnaire dealt among others with socio-economic characteristics of residents and trips generated in each urban centre. In this study, socio-economic characteristics are used to refer to social and economic status of the households.
Other important measures considered as potentials of household trip generation in this study are: length of stay, number of workers, mode of travel and estimated annual rent paid. The annual rent paid is considered here as another measure of economic power aside income as previous studies have shown that in survey research, respondents often inflate incomes for ego boosting or deflate them for tax evasion.
In all, twelve socio-economic characteristics of households are considered important measures of travel behavioral pattern and determinants of trip generation.
Multiple regression technique is employed in this analysis. The stepwise version of the model was used because it derives the best regression equation from a set of explanatory parameters in a step-by-step version. According to Hauser (1974), the stepwise regression model is a search procedure, which identifies the independent variable, which possesses the strongest relationships with the dependent variable. The model thus helps to eliminate such independent variables that do not make any meaningful contribution to the explanation of the dependent variable.
The explanatory variables are considered one after the other on the basis of their partial correlation with the criterion (dependent) variable. The independent variable which exhibits the highest partial correlation with the criterion is considered first in the regression equation while the one with the greatest proportion of the residual variance is considered next.
At every stage of the analysis, a significant test is carried out using 'f' and 't' test statistics to ascertain the reliability of the variance that is contributed by any newly entered independent variable in the overall relationship. The outcome of the analysis is presented next.

RESULTS
The socio-economic determinants of trips generated vary both in number and magnitude among urban centres. As shown in Table 2, there are some characteristics that contribute significantly to the criterion in some urban centers and not in others.
The magnitude of significant variables reveals different patterns from the number of significant variables, across the cities. While the more developed urban centers like Abeokuta, Ijebu-ode, Sagamu and Ota have higher number of significant socio-economic determinants of trips, the less developed ones like Iperu, Ado-odo, Owode and Ilaro account for higher proportion of magnitude of significant variables. This shows that socio-economic characteristics of residents provide a higher explanation of trip generated in emerging urban centers of Ogun state, Nigeria than in the much more developed cities. In other words, at the early stage of urban status, socio-economic characteristics of urban residents provide a higher    Education level 4 7 Length of stay 6 8 Income 7 9 Rent 5 10 Auto ownership 2 11 Mode of travel 3 12 Number of worker 13 explanation of trips generated; but as the urban centre develops further, the influence of socio-economic characteristics of residents, reduces in magnitude as determinants of trip generation. This suggests existence of other factors aside socio-economic characteristics of residents affecting urban trip generation as the urban centres advance in growth and development. There is therefore the need to include level of socio-economic development of urban centres in future research on intra-urban travel behavior. The frequency at which each of the explanatory variables entered into the regression equations is shown in Table 3 and worthy of consideration. If the frequencies can be taken as an indication of the importance of the variables, then, number of workers per household is the most important. This is followed by age, income, length of stay and rent in that order. Other variables follow as shown in the table.

CONCLUSION
The influence of socio-economic characteristics of households in urban trip generation is examined in this study. The socio-economic determinants of trips generated vary in magnitude and number from one urban centre to the other in the state. The number of significant socio-economic determinants of trips in more developed urban centres like Abeokuta, Ijebu-Ode, Sagamu and Ota is more than in the less developed ones like Ilaro, Iperu, Idi-Iroko among others.
Also, as shown in this study, the level of explanation of criterion provided by significant socioeconomic variables varies among urban centres. The socio-economic characteristics of residents are more effective as determinants of urban travel behavior in emerging urban centers than the more developed ones. This as earlier suggested implies other factors aside socio-economic characteristics of residents affecting trip generation. In this regard, the influence of spatial attributes of urban centers has been suggested for consideration for further study in urban trip generation.
In the light of this finding, travel behavior in urban centres should be monitored on continuous basis. At the initial stage of development, socio-economic characteristics of residents should be given due consideration. However, as city develops further, other factors such as physical features/components should be given consideration in an attempt to understand and adequately plan for efficient urban travel.