Nikon D70 Night Train Watching
Never tried this myself. But how dark is it likely to be? How sharp does the photo have to be for your cataloging/collection? Also are you talking modern or possibly steam power?
To reduce blur caused by movement, could you position yourself so that you are not trying to photograph side on, Perhaps use a position where the loco will be moving more diagonally as this will reduce motion blur to some extent.
The D70 (If its like my D50) would be about usable at ISO 800 max provided you shoot raw and post process in something like Lightroom. But in any event you are up against it if you want pictures at a sharpness level that is possible in daylight with an older camera body. If you could stretch to buying a D3200 it would have much better low light capability.
Other than that some supplementary lighting will be necessary.
If its a steam loco, go for atmosphere, pan and get some blur it will add to the photo!