I made a curve in the shape of what I want my polygon objects to follow in. I remember some option in animation buttons that let you clone an object many times making it follow a path. But I can not remember anymore how to do this 
For example, I can make an ellipsoid farris wheel, and make all the chairs duplicate along the curve spaced out out in proper sequence.
Make the curve the parent of your object.
Select the curve and go to the animation buttons (F7). Press ‘CurvePath’, ‘CurveFollow’ too if you need it.
Now select (only) your object and in the same buttons set dupliframes.
You can play with DupSta(rt), DupEnd, DupOn, DupOff ; on the curve side PathLen is interesting and can be replaced by a speek IPO for more flexibility, which could proove the only solution for you to get a precise number of (how do you call them ? Cars, benches, buggies ?) in just the right places.
Also, to complement Jean’s answer, here’s how the Speed IPO works.
First of all, it’s always good to know where it’s located, isn’t it? Well, the Speed IPO is located under the Curve tabs, the icon looks like the one of the Animation Buttons.
There, you can create and edit the IPO curve just like normal. You can add points with Shift-Left Mouse (be sure to select the IPO name in the collumn at the right of the screen before), and edit them like a bezier curve.
The value of the Speed IPO correspond to where the object will be on the curve. A value of 1 means that the object is at the end; 0, at the start; 0.5, in the middle; and so on.
Hope that helps
Martin