Horseshoe Curve

 

This low level oblique aerial photograph is looking easterly above the Horseshoe Curve of the Pittsburgh to Harrisburg line. Altoona, PA is in the top center of the photograph. The line over the Allegheny frontal was designed by J Edgar Thomson of the Pennsylvania Railroad. The Gallitzen tunnel at the top of the grade from Altoona was completed January 21, 1854. The Pennsylvania Railroad withdrew the traffic it had been moving over the frontal via the New Allegheny Portage Railroad on February 15, 1854. While the civil engineering demonstrated by Thomson in the 1850's was remarkable, if he were designing the line today there would be no Horseshoe Curve. The grade combined with the curvature that binds wheels requires extra tractive force to move trains. Tractive force is a measurement of force needed to overcome gravity in moving a train. riding around the Horseshoe Curve is a fine and memorable experience. The best viewpoint is from the cab of the locomotive. Watching trains round the curve appeals to the senses as machine works against gravity.

So, if Thomson had diesel powered, hydraulic activated equipment and modern explosives instead of manual tools, men, horses and black powder, how might the line over the Allegheny frontal been designed? How might the line have not exceeded a 1% grade?

Note: Photos by http://www.galacticafanfic.com/flying/flying.html