[Big Dave]

I think Cajon Pass grade is 1.1%. The theoretical max grade for steel wheels on sanded steel rail is about 6% for the locomotive only.

As a rule one uses a cog railway in excess of 5%.

Back on topic, it would astound you how far trains can coast. Quite often you pass the "ruling grade" and coast 50-70 miles or more to the division point. For instance on the old B&O (now CSX) St. Louis division the ruling grade westbound was at Loogootee Indiana. Once over this grade, the train coasted all the way to Cone Yard in East St. Louis. Yep. The train coasted all the way across Illinois and was on the brakes just outside Cone.

Trains are 4-8 times as fuel efficient as rubber-tired vehicles, but they are terrible for door-to-door service.