Study On Relationship Between Road Alignment And Traffic Safety For Two-Lane Highway

The safety is a main factor among numerous demands of travelers. The extentof focusing on safe problem and providing safe guarantee and individuation servicefor highway user is not only test on government power and significant test oncapacity of researcher dedicating highway safety. Traffic accident results frommaladjustment of one or several factors in the system that is composed of people,vehicle, road and circumstance. Thereinto, traffic safety connects with highwayalignment.This dissertation is supported by science and technology project of westtraffic construction by ministry of communications "forest tourist highway——traffic safety research on S203 of Inner Mongolia. The author firstly analyzeoperating characteristic of vehicle on two-lane highway and effect of roadalignment on traffic safety, then analyze the relationship between highwayalignment condition and accident rate depending on changeable characteristic ofvehicle operating speed. Through forecast on operating speed of correlative section,the author consider changeable value of operating speed as guide line forestimating continuity and safe condition of road. It can provide basement forhighway design and rebuilding. There are six chapters in the dissertation. Theemphasis are the third, the forth and the fifth chapter. The core is the forth chapter.The first chapter introduces research background, actuality, significance andcontent. Facing the actuality concluding higher severe extent of road trafficaccident and higher acceleration of the number of accident and casualty, it isnecessary to improve level of traffic safety and lessen accident disservice. Theauthor carefully analyzes the relationship between geometrical essential of roadalignment and traffic safety, especially the effect of two-lane highway alignmentwhich occupies 95% in highway net on traveling safety. It is great significance forforecasting and lessening traffic accident.The second chapter introduces traffic safety condition of two-lane highway.The investigation data show that the second and the third grade highway havehighest frequency in traffic accident and casualty. Through analyzing accidentmodality characteristic of two-lane highway, we discover that over-speed andovertake running affect safety greatly. On two-lane highway, driver wants toovertake the slower vehicle at any moment. But overtaking need occupy anotherreverse lane, overtaking easily result in traffic accident. Casualty and severe extentresulting from overtake accident is higher then non-overtake. So we advise to setspecial overtaking lane on the two-lane highway when there is higher daily averagetraffic volume and higher speed. Over-speed is another importance reason fortraffic accident on two-way highway. The traffic accident resulting from over-speednot only occupies comparative proportion but most is significant accident. In fact,over-speed also exists on freeway and first grade highway. But the phenomenon ofvehicle mixed running is more severity on two-lane highway. Over-speed of partvehicles make overtake probability increased. Speed distributing of vehicles onroad is more discrete and it make the accident probability increased greatly. Thischapter analyzes the reason that continuous downgrade section of two-lanehighway is the cause of frequently occurring accident is out control of vehicle forover-length of braking distance and invalidation braking.The third chapter introduces the effect of each guideline of alignment designdepending on geometrical design essential of plane, verti concretely and transectsand traffic safety in detail. It is indicated that road alignment design consider notonly demand of vehicle operating kinematics and dynamics but amenity ofalignment. In additional, it is need to consider traffic condition of adjacentalignment and concretely analyze its operating speed. Otherwise, highwayalignment with potential accident will be designed. In order to analyze the effect ofgrade on running of vehicle, we choose 8t freight vehicle, and observe its speedvalue on different upgrade and downgrade under free flow condition. Then therelationship between average speed of freight vehicle and grade is gained.The forth chapter analyzes the effect of traveling distance on traffic safetybegan with the relationship between traveling distance and accident probability.Distance setting and several importance considered aspects of test is expatiate indetail, it is very important for the considered aspect of road safety test. This chapteranalyzes proper combination and combination should be avoided of horizontal andvertical curve, and indicates significant relationship between rationality ofcombination of horizontal and vertical curve and safety.The fifth chapter analyzes alignment design basement in popular TechnicalStandaral of Highway Engineering, disadvantage of design speed, synchronouslyexplain the advantage of operating speed that is created and researched itsapplication by USA and Australia and estimate criterion of alignment continuityusing by Leich and Leich and Lamm et al. The author establishes forecast model ofoperating speed base on two-lane highway alignment integrated research result ofAustralia Guideline of Highway Design and our existence. The model firstly carvesup analytic unit of selected section depending on radius of horizontal curve that canadopt different principle on line and various curve sections. It is considered thatradius value of horizontal curve and requirement of vehicle running transversestability and comfort on smaller radius curve. The author integrate design essentialof transect, and compute operating speed controlled by horizontal curve throughVB programmer. In order to make the forecast model have better applicability, theauthor consider the special vertical grade that are either grade exceeded 2% andslope length exceeded 500m or grade exceeded 3% and slope length exceeded300m. Aim at the factor which is only qualitatively described and not quantitativelycomputed, the author imports effect factor and then forecasts operating speed valuedetermined by condition of road alignment. Application with this model, operatingspeed of section between K463+791 and K468+994.5 of S203 in Inner Mongolia isforecasted and compared analyzed with observed data in field. The author analyzesalignment continuity through forecast result of operating speed and find out threediscontinue locations of alignment in this section by referring to estimate criterionof continuity. Accident observed information show that two of these are locationsof frequently occurring accident, then veracity of forecast model is proved.The sixth chapter concludes the work in the dissertation and brings forwardcontent and direction that will be continuous to researching.