中文摘要：

以重庆市38个区县公路网络为研究对象,以最短距离为原则,在构建公路网络拓扑结构的基础上,计算加权平均旅行时间指标和通达性系数来衡量城市通达性水平的高低,并对通达性水平的特点和空间格局进行分析。结论如下：（1）38个区县的通达性水平呈现出＂放射状同心圆＂特征,以重庆市主城区为圆心,随着同心圆的半径增加,通达性水平逐渐降低,形成明显的环状分异态势;（2）路网的拓扑连接水平较低,路网等级体系不够完善,网络的辐射效率不高,网络结构相对脆弱,网络的有效性较低;（3）高等级路网发育不均衡,区县间出现通达性差异很大的现象,影响区域的协调发展。

英文摘要：

The road networks of 38 counties in Chongqing were chosen as the research object in this paper. Under the principle of the shortest distance and on the basis of the road network topology structure, the weighted average travel time index and the accessibility coefficient were calculated to measure the accessibility level and its spatial pattern of the road networks in Chongqing. The conclusions are as follows：（1） The accessibility of the 38 counties shows the characteristics of the radial concentric circles with the main urban area as the center of the circle. With the increase of the radius from the concentric circle, accessibility level gradually reduces and forms obvious annular differentiation situation. The main districts and the near districts and counties around maintain high accessibility level and the accessibility level gradually reduces with the increase of distance, while the remote districts and counties have low accessibility and inconvenient transportation.（2） The level of road network topological connectivity is low, which leads to the system of the level of road network not perfect enough and low efficiency of the network radiation. The transportation axis with high connectivity are scarce and the dense parts are mainly distributed in the main districts, which contributes to relatively weak network structure and low effectiveness of the network. The overall network is low and ＂blind spots＂ exist in the network the high grade road, which weakens the efficiency and level of the existing network. The road network is expected to extend and expand.（3） The network of the high grade road is in disequilibrium, which leads to sharp differences in the accessibility among different districts and counties affecting the regional coordinated development. High grade road especially highway has significant impacts on regional accessibility. The expressway ring built up in the main districts extends outward presenting a radiation structure. The core city circle has high accessibility, but the rad