To analyze the risk factors influencing the crash injury severity in rural-urban fringes, crash data in rural-urban fringes were collected from Harbin, China. Four risk factors, namely, time of day, vehicle type, road feature, and crash type, were investigated associated with the severity of rural-urban fringe crashes. The crash injury severity was divided into two categories, including fatal and nonfatal crash. The logistic regression was applied to explore the relationships between the severity outcomes and time of day, vehicle type, road feature, and crash type. The test methods of goodness-of-fit and badness-of-fit are conducted to examine the validity of estimation results. The results show considerable matching of the number of different crash types between calculated results and actual data. Compared with the other influencing factors, the time of day is significant factor for crash injury severity based on the study. As such, the proposed calibration procedure and the factors of choice are recommended as a validated approach to analyze and identify the main factors influencing crash injury severity in rural-urban fringes.
According to the tracking observation of the highway subgrade moisture content in the high-latitude and low-altitude seasonal frozen ground region in Heilongjiang province, the time-varying variation law of the subgrade moisture content and the distribution state of the subgrade moisture content at different depths are analysed to confirm that the distribution pattern of moisture content in fine-grained soil subgrade does not strictly conform to capillary ascent distribution law of groundwater (or surface water), which is related to the coverage and gap of the pavement, slope water seepage and water-holding capacity of the subgrade soil. In general, the distribution state can be roughly divided into B distribution, C distribution, D distribution and S distribution. As the distribution of subgrade moisture content is no longer the conventional pattern of “low up and high down”, the control of subgrade height should not be rigidly stuck to the subgrade height controlled by capillary ascent height, while multiple measures should be taken to ensure water temperature and strength stability of subgrade.
Drainage base can effectively maintain the service performance of asphalt pavement structure in cold and humid areas, and improve its service durability. The void ratio of drainage base asphalt mixture shall be more than 20%, and the asphalt content is generally between 3.15% and 3.55%. Five kinds of open graded asphalt macadam mixtures were selected and tested for structural performance, water permeability, mechanical performance and water temperature stability. According to the test results, it is shown as follows. The water permeability coefficient of the five kinds of asphalt mixtures at 15°C was 0.10-0.19cm/s. The ratio of freeze-thaw splitting strength was 72.1%-92.3%. The compressive strength of uniaxial compression test was 4.53-8.91MPa. The compressive modulus of resilience was 794.79-1236.51MPa. The maximum bending tensile strain of beam was 3150-4977με. It has good structural strength, water stability and drainage performance. After 10-50 freeze-thaw cycles, the performance of structural performance index, tensile strain and mechanical index of asphalt mixture is well. The asphalt mixture can be used for drainage of asphalt pavement structure in high-latitude and low-altitude cold area. The recommended suitable layer is the upper base or lower layer of asphalt pavement structure.
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