The parabola is generally used for the curved cross section In that case the

The parabola is generally used for the curved cross

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The parabola is generally used for the curved cross section. In that case the crown of the pavement is slightly rounded, with the cross slope increasing toward the pavement edge. These are difficult to construct but are better at draining surface water. Side Slopes Side slopes are provided on embankments and fills to provide stability for earthworks. They also serve as a safety feature by providing a recovery area for out-of-control vehicles.
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DESIGN OF CROSS SECTIONS Lecture 6 13/04/14 11 When being considered as a safety feature, the important sections of the cross slope are the hinge point (top of the slope), the front slope, and the toe of the slope (I.e. the intersection of the front slope with level ground or a ditch). Hinge Point. This contributes to a loss of steering control, since a vehicle leaving the carriageway tends to become airborne when crossing this point, particularly, if embankment drop off is severe. The front slope region is important in the design of long slopes where a driver can attempt a recovery manoeuvre or to reduce speed before impacting the ditch area. It is instinctive for an erring driver to attempt to return to the carriageway, and there is a front slope steepness at which a vehicle will roll during this recovery manoeuvre. HINGE POINT BACK SLOPE FRONT SLOPE
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Lecture 6 13/04/14 12 DESIGN OF CROSS SECTIONS Toe of the slope . In many instances, the toe of the slope is close enough to the carriageway that the probability of a vehicle reaching the ditch is high. In such situations, safe transition regions between the front and back slopes should be provided. Research has shown that vehicle rollover need not be a problem at the hinge-point region of an embankment with a slope of 2 horizontal to 1 vertical (or flatter). Rounding of the hinge points reduces the tendency for errant vehicles to become airborne and the consequences. If sufficient recovery distance is available, return manoeuvres can be accomplished on embankments of 3:1 or flatter at 130kph without vehicle rollover. Usually a trapezoidal ditch cross section is the safest for vehicles to intrude at FOR STEEPER SLOPES ON HIGH EMBANKMENTS, STOP THE VEHICLE FROM LEAVING THE ROAD WAY (Crash Barriers!!!)
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Lecture 6 13/04/14 13 DESIGN OF CROSS SECTIONS Medians A median is a section of a divided highway that separates the lanes in opposing directions. The functions of the median include: Providing recovery area for out-of-control vehicles Separating opposing traffic Providing stopping areas during emergencies Providing storage areas for left-turning and U-turning vehicles Providing refuge for pedestrians Reducing the effect of glare of headlight Providing temporary lanes and cross-overs during maintenance operations Medians can either be raised, flushed or depressed.
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