Abstract: Construction of road infrastructure is a fundamental aspect of the city operation and development, as well as an important pathway and focus to realize the physical urban-rural integration. The long period implementation of "ring + radiation" road system in Beijing has brought a major impact on its urban infrastructure construction and its time accessibility. Particularly in recent years, the rapid increase of private cars in Beijing has become a greater burden to its road system, which has in turn seriously hampered the urban commuting efficiency and added the costs to people's lives. To deal with such challenges and enhance the frog-leap development of transport infrastructure, Beijing has speeded up its development pace in light railway construction since 2008, so as to improve its commuting capacity. This paper tries to measure the time accessibility and its spatial characteristics in the urban areas of Beijing by applying a combined method of vector and raster attribute data generated from major roads and rail transport infrastructure. By using a dual index of accessibility and road density, the paper further reveals the features of spatial accessibility and construction of road systems in the urban areas of the capital, as well as their different presences in the northern and southern parts of the city. The findings of this paper could provide a scientific basis for future urban planning and road system construction for Beijing Municipality.

Key words: accessibility, road density, spatial characteristics, Beijing