I'd have to cast my vote for flaggers. (no recounts either...) My reasons are -
1. Cost to aquire, install and maintain proper crossing protection could be stunningly high.
2. These crossings are for the most part in isolated, rural areas. As a result, every knuckle dragging, gun toting yahoo will be tempted to display his shootin' skills by blowing the signals into the hereafter. That brings you back to the maintainance part of #1.
3. Seven months out of the year these signals will be unneeded.
4. For three or four of those months the signals may well run the risk of getting whacked by state snowplows.
5. People have shown an amazing willingness to blow through or around protected crossings. (the same can be said for flagged crossing, but try programming a crossing gate to lob a lit fusee through the window of a passing car..)
6. Two people in a vehicle could man and flag all of the crossings, in addition to being on hand for other needs (fires, mechanical, minor medical, ect.)
7. To a limited degree, properly trained volunteers could assist in these tasks. Or, a couple of folks assigned to other jobs on the railroad could perform these tasks on a rotating basis. Worst case, hire some folks to flag crossings on a part time basis.
Those are my thoughts and ideas, fire away! sda