   |
 A new transportation engineer is charged with the design of a horizontal curve for the Queen's Highway in Canada. His final design calls for a curve with a radius of 520 meters. Would you sign your name to his plans? Assume that the design speed for the Queen's highway is 110 km/h. You can also assume that snow and ice will be present on the roadway from time to time (it's Canada). [Solution Shown Below]
Solution The first step in a review of his plans would be to make sure that the curve radius as designed is greater than the minimum curve radius. For a design speed of 110 km/h, the comfortable side-friction factor is 0.10. In addition, since the roadway will be covered with snow and ice from time to time, the maximum superelevation rate is 8%. With this information we can go ahead and calculate the minimum curve radius using the equation below. Rmin = V2/(127(emax/100+fmax)) Where: Substituting and solving yields a minimum radius of 530 meters. The 520 meter radius that is called for in the plans would probably work, but it might be uncomfortable for the vehicle occupants. A larger radius would be more appropriate.
|