Parameter Optimization And Safety Evaluation Research Of Highway Geometric Design

In the traditional highway geometric design,deterministic approach has been widely adopted in China in the past decades.The usual way is to firstly determine road grade and design speed,and then choose the relative geometric indexes according to Chinese specifications--JTG B01-2014 Technical Standard of Highway Engineering and JTG D20-2006 Design Specification for Highway Alignment.The design complying with the specifications were considered to be legally apropos.However,there still existed two potential problems using this design method,one of which was how to guarantee the safety level of highways while only upper limit values(or lower limit values)were provided in the specification without restraints for general values,and the other one was whether the combination of indexes could meet the safety requirements with each index satisfying the requirements of specification.Apparently,it was difficult to answer these two questions using traditional design methods.At present,safety levels of parameters which were not restrained in the specification were mainly controlled by designers,leading to the randomness in the selection of road design parameters,where existing risks of malicious overdraft of the specification.In order to quantize the adoption of index values,design parameters were viewed as variables and introduced into the probability design theory.For the combination of indexes,three-dimensional evaluation methods were selected for the judgement of alignment design quality in consideration of the spatial nature of roads.A synthesis was developed in the first chapter of this dissertation to address current geometry design principles,safety audit methods and highway alignment situation.13 clincher geometric parameters were particularized with the combination of the American specifications.Based on simulation experiments conducted using UC-win/Road and the virtual prototype in Adams/Car,the effect of road geometry on human factors and vehicle performance was then discussed,and correlations between drivers’ physical and psychological responses and dynamic performance parameters with some design indexes were also analyzed.For index optimization and quantitative analysis,reliability methods have been incorporated to investigate to analyze each design index.In consideration of the safety effects of human-vehicle system,the limit state equations were constructed and the numerical calculation of the first order reliability or the Monte-Carlo simulation sampling method was utilized respectively to calculate the reliable values of minimum length of planar tangent,length of vertical slope and widening indexes of cross sections.After the quantization of index adoption,sensitivity analysis was conducted to provide recommended values calculated by reliability method and its application slope.In view of the spatial nature of road alignments,parametric equations were established on the basis of stakes,and evaluation model was constructed to determine the continuity of road alignments with spatial curvature and torsion variance.Considering the difficulties in the construction of real three-dimensional dynamic design platform,the study eventually considered the spatial performance of alignment combination on the basis of two-dimensional design,and determined comprehensive evaluation parameters for road alignment in the human-vehicle-road environment for the safety evaluation of three-dimensional operation condition of road alignments.