Research On Theoretical Operation Velocity Versus Highway Alignment Design And Their Evaluation Methods

Whether or not the highway alignment is properly designed will directly affect the safetyof highway operation.Highway alignment design must meet the requirements for vehicleoperation characteristics,with emphasis on selecting a rational combination of horizontal andvertical alignments to assure the equilibrium,consistency and continuity of highwayalignment indices,and to meet the demand for high-speed and safety operation of highways.In view of the limitations of the existing speed-based design methods of China,this thesispresents the research on theoretical operation speed models,the theoretical speed-basedhighway alignment design methods and their evaluation methods.The purpose of the researchis to establish a theoretical prediction model that is closer to the actual vehicle speed under agiven highway alignment condition.The model can be used to guide highway alignmentdesign,and the alignment index selection and alignment safety evaluation.On the basis of the effect and restriction of design speed and operation speed V85 used inalignment design and evaluation,a new concept'theoretical operation speed'is established.Theoretical operation speed is the running speed when running is only influenced by thedriver's operation behaviour,automobile mechanic power performance and highwayalignment itself under the condition of free flow in good road conditions.The thesis analyzesand discusses the methods and steps for the alignment design and the alignment continuityevaluation based on the theoretical operation speed,and discusses the application of thetheoretical operation speed used in the alignment design and revision.The establishment of this model takes full consideration of the factors like:pedestrian,vehicle and road.According to the principle of automobile power performance,the thesisinvestigates different influences factors on the operation speed,such as vertical,plane,crosssection and combination of horizontal and vertical alignment,a theoretical operation speedprediction model based on the highway alignment is established by comprehensivelyconsidering the performances of automobile power,braking,running,control,and driver'scomfortability,safety and operation behaviour.The expected speed of the car and truck isdemonstrated by analyzing the driver's operation behaviour and the speed continuity;Basedon the automobile's power and braking performance,a speed model based on verticalalignment is established considering the shifting gear in upgrade and braking in downgrade;The thesis studies the process of automobile acceleration and deceleration,running comfortand the drivers' controllability on plane curve,and the critical radius when plane curve has no influence on the theoretical operation speed;and establishes a speed model based on thevertical alignment.For the theoretical speeds predicted based on the plane and verticalsections,the small one is the major speed,and the big one is the secondary speed.The latter isused to improve and optimize the former one with consideration of different vehicle types,and then the speed model based on the combination of horizontal and vertical section isestablished.The influence of vertical section on the theoretical operation speed is solved byestablishing models of the influence factors to get the discount value of the speed.Model ofthe theoretical operation speed established in this thesis suits for the speed predicting ofdifferent vehicles like cars and trucks in different classes of highways.With the test data insitu,the model has been proved to be reliable.Design speed,used as the controlling criteria in the current highway design,decides theminimum index value in of alignment design elements,while the actual running speed is animportant basis to check whether alignment design indexes are reasonable and the relationsamong them are suitable.The variation ratio of operation speed reflects the harmonies of thealignment indexes and the continuity of alignment design.Therefore,the design andevaluation methods developed in this thesis are in fact to add a new design-check stage in thecurrent design using the theoretical operation speed,then the technical alignment indexes ofthe horizontal and vertical alignment can be checked and revised using the theoreticaloperation speed to meet with the related specifications and operation speed consistency,tomeet the needs of alignment continuity and speed consistency,and to satisfy the runningsafety requirements.Through research on the relations between theoretical operation speed and design speedand relations between variation ratio of theoretical operation speed and alignment indexes andtheir combination,all the evaluation indexes have been improved,integrated andsupplemented based on the model of theoretical operation speed with the core of continuityindexes.This thesis establishes a complete and systematic alignment safety evaluation systembased on the graded discusses,studies the structure of safety evaluation system,proposes acalculated model,weigh coefficient and evaluation criteria of every evaluation indexes,showssteps and processes of alignment safety evaluation,and proposes a quantified newevaluation index-Alignment Safety Index (ASI).On the basis of alignment-based theoretical operation speed model and research onalignment safety evaluation index system,prediction of a highway safety evaluation systembasing on the theoretical operation speed is designed and developed.The thesis introduces the system demand analysis,framework,overall design,functional design and system realization,and focus on how to realise the functional modules,like alignment compliance check,roadsection division,theoretical operation speed prediction,alignment technical index evaluation,safety index quantifying,etc.Reasonability and feasibility of the theoretical operation speed prediction model andalignment safety evaluation system have been verified in the practical projects.Therefore itcan provide basis for the highway safety and continuity design.