As others have mentioned, anywhere along the BNSF Transcon there will be a lot of trains. If you don't have much time or want to keep moving, Kingman Canyon and Crozier Canyon can provide satisfying photography without straying too far from the highway, or even on the shoulder of the road. There's also Nelson Tunnel (slow going to get there) and the Canyon Diablo bridge (VERY slow going to get there) if you have time to get off the beaten path. If you get to Kingman in the afternoon you can get some nice golden hour shots in Kingman Canyon (be aware of the canyon wall shadows, they show up well before sunset), and then in the morning you can go east of Kingman a few miles and get some really nice desert shots before and after sunrise. Well worth getting up early for.