Public transportation system has various effects on the advancement in the world.
For instance, it provides link between where people live and where people work, and between manufacturers, service providers. Transportation facilities give opportunities for different activities such as work, shopping, recreation and allow people to reach hospitals, schools, etc. Since the 1820s, several forms of public transportation have come and gone throughout the world, making an influence not only on how people travel but also on the morphology of cities. Since the 1970s the interdependencies between population structure, urban form and travel are developed as a research field in spatial sciences and transport sciences .
There is a close relationship between urban transport and urban structure and land use. In third world cities rapid urban expansion driven by rural –urban immigration leads to many new arrivals in cities, causing people to forcefully live at distant areas from their activities. The real meaning of mobility or the true goal of transport is access . However, the land space devoted to circulation is often below average in proportion with rapid population growth . Hundreds of people in the region do not have access to basic social and economic services only due to poor access to transport infrastructure and services. Urban planners still rely on technical and constructional approaches, without thinking deeply in everyday services, causing low portion of people using public transportation system, and the negative the image of the public transport as the mean of the poor.
2.2. The link between public transportation and land useLand use is the representation of all kinds of urban activities and characteristics of city, such as all urban infrastructure, transport flow, social and economic activities and population. All the elements that compose urban can be found in the land use; purpose of land, development intensity, population density, residents and jobs density, car ownership, goods circulation and so on are included in urban land use. Urban land use scale, spatial patterns, structure and proportion of different land can figure various urban forms.
Land use is considered as the basic source for transportation, it defines the different types of transportation trips and increases the transportation demand. Many scholars have paid a lot of efforts on how various characters of land use affect the public transportation system and on how public transportation system affects land use. Based on literature, land use factors that play main role in planning for public transportation routes can be summed in; housing density which is reflected in population density, land use design presented by commerce services and the main attractions of the city locations, and pattern (such as land use structure). In 1977, Knight summed up various factors that affect urban land use, he included accessibility, land connection and land policy, and emphasized on accessibility as the most important factor that affects the land use, in addition to the construction of new transport facilities could also enlarge urban land use accessibility and attractiveness of the surrounding land that results in the land price rise. 2.3 DensityDensity means the number of people or employment in an area. It can be measured by the number of residents, housing units or employees per acre .
According to a research performed by Newman, Kenworthy, Laube, Barter, Raad, Paboon, and Gulia (1999) covering 46 major cities around the world, it concluded that “the more centralized is the city in terms of both population and jobs, the less auto dependent it will be and the less transportation energy it will use”. Fouchier (2000) carried out a research about auto ownership and mobility; he reported that as density increases auto ownership decreases. Additionally, he determined that in low-density outer region of Paris people prefer using automobile because of longer distance between residence and employment, lack of public transport and convenient parking place. In high density inner part the situation is totally inverted. Automobiles do not attract people because of cost and scarcity of parking place and congestion. Easiness of public transport is another factor for people not to choose private autos.
In another study by Holtzclaw (1994), effects of household density, accessibility to public transport, accessibility to neighborhood shopping and pedestrian and bicycle accessibility on vehicle miles of travel using data of twenty-eight communities in California were investigated, he hypothesis that, residents drive less when they live in communities with higher densities, more transit service, nearby shopping (restaurants, markets, drugstores, etc.) and pedestrian friendly environment was tested. 2.4 Roadway Connectivity Connectivity means the directness of links and the density of connections in path or road network (VTPI, 2007). Connectivity implies a system of streets with multiple routes and connections serving the same origins and destinations; it relates not only to the number of intersections along a segment of street, but also to how an entire area is connected by the street system (Community Planning Workshop, 2003).
