Use Type on a Path with a lower case "L" and adjust the tracking.
Create a pattern brush. And be careful not to convert strokes to paths in your brush shape
Or, if you actually prefer lines and intervals to be proportional, in other words being wider/narrower away from the path in curved paths, you may use a high Stroke Weight and Dashed Line; for the latter, up to CS5 you may use the free Adjust Dashes script available at
to give a nice distribution.
Or you may use a rectangle for the Pattern Brush.