Site Distance Equation for Crest Vertical Curves Research Paper

Site Distance equality for Crest Vertical Curves - Research Paper ExampleThe elevation of various points of the curve gives the relative inequality in the level at different points on the curve. Also shown in the figure are duration of the curve, start of the curve and also the end of the curve. To provide easy movement of fomites and also to smooth go forth the tumid profile the vertical curves are introduced at the intersection of the grades. Usually two type of vertical curves are used in the geometric design of roads. They are vizor curves or summit curves and drop down curves or valley curves. The meridian curves have the convexity upwards and when a fast moving vehicle travels along the curve, upward action of the centrifugal force against the gravity and would relieve a part of the mechanical press on the tyres. This phenomenon would eliminate the discomfort experienced by the passengers wouldnt feel the discomfort while passing everyplace these curves (Garber and Hoe l, 2001). The process of aligning the vertical curves along the road is influenced by various factors like the vehicle speed, acceleration, tenia position distance and comfort in travel (Wright and Dixon, 2004).The design of the summit curve is governed only by sight distance con facial expressionrations. Though the circular upper side curve is an ideal choice as the sight distance available throughout the continuance of a circular curve is constant most of the designs favor parabolic curve. This is because the deviation angles in the vertical curves of highways are very small and between the same tangent points a simple parabola is congruent with a circular arc. In addition, easiness in computation of the ordinates also the better rising comfort given by crest curves gives preference to parabolic curves (DRMB, 1993). When the parabolic crest curves are adopted the equation is given as y=ax2 , where a = N /2L. The N in the equation is the deviation angle and L is the length o f the curve. Since the crest curves are long and flat , the length of the curve L is taken as equal to the horizontal projection. During the process of the design of the parabolic crest curves it is necessary to con spatial relationr the stopping sight distance and overtaking sight distance separately. As indicated earlier, it is innate to provide sight distances atleast equal to the stopping distances at all points on the highways to avoid the accidents due to poor sight distance (Garber and Hoel, 2001).Figure 2 The length of the crest curve is greater than the stopping side distanceLength of the summit curves for stopping side distance.The two situations that need to be considered in the finish of length of the curve for stopping side distance (SSD) are (i) When the length of the curve is greater than the side distance (L SSD) and (ii) When length of the curve is less than the side distance (L For L SSD (Figure 2), the length of the vertical crest curve is given as---------- -------- (1) Where, L is the length of the vertical crest curve in metre, S is the stopping side distance in metre, N is the deviation angle which is equal to algebraic deviance in grades, radians or tangent of the deviation angle, H is the height of the eye level of the driver higher up the road surface in metre, h is the height of the object above the pavement surface in metre. The value of H