BNSF ES44C4 test3
And now another one for Uncle Warren (not really my Uncle.) A C4 is basically an ES44AC with A1A trucks. The idea behind the real one is to increase tractive effort at speed. Tractive effort diminishes with speed, so by raising the center axle while under way, more weight can be added to the driving axles. Trios of these guys run constantly between Long Beach, CA and Chicago. I haven't heard how well they really perform, but so far BNSF are the only buyers.