Test mile on the Harrisburg Line

[theWatusi]

Yesterday I took a trip down to Valley Forge Park. I parked at the old Betzwood station and meandered west for a bit. At Forge there is a mile post marker (22) that says "Begin Test Mile"

Anyone know what this means?

BTW I was there for about 2 hours and saw 3 Eastbounds and one Westbound.

[gp80mac]

It's a measured mile that is to be used to test the accuracy of a locomotive's speedometer. There is an accompanying sign a mile down the track that says "End Test Mile". So you try to keep your speed constant in that mile, then you can figure out your speed and compare it to what the speedometer says. Then you can let the next crew know how accurate the speedometer is. And if it's off by too much, you can report it.

Why are there special test miles? Because the other milepost signs do not always correspond to the actual mile. (on the HBG line, there are several 2 mile long miles or 1/2 mile long miles )