You can set position keys on different control points for the prop to approach. You can even set variations in speed for the prop while moving on a path. This can be used to simulate something moving very fast and then very slow or when something is very slow and then enters high speed. There are few examples, such as when a person is walking uphill or when a car suddenly goes downhill.
When you have selected the position keys for picking path on a target control point, you can then see the keys under the target prop's Constrain/ Path in timeline.
Since there are several keys set for picking path, you can then drag and pull these keys to set the speed for it to get to the destination in the limit time of frames.
Now adjust the key to frame 100. You may now see the bus runs even faster to get to the destination in these frames.
You can even set a variation in speed between position keys in the timeline.
Please refer to Transition Methods in Tracks for more information on Transition Curve.
Once you have selected a curve, the behavior affects the keys you have just set with the previous position key.
