How does grade affect acceleration?

[rkagerer]

Does going downhill help a train accelerate faster?  Does going uphill make it decelerate faster?

I'm wondering because on the Great Divide campaign I want to make a station like this:

I'm wondering if the 3.5, 3.0 and 2.0 grades will help or hinder trains leaving the station toward the bridge or arriving at it from the direction of the bridge.  (For the purpose of discussion let's pretend that's a stone bridge not wood).  In theory if the answers to both questions are "yes" then this seems like a great setup - departing trains get a little extra help rolling out and arriving ones find it easier to brake.  But something makes me suspect the game isn't going to cooperate with this theory...

[jeffryfisher]

Grades only slow trains going up.