Don't expect this antenna to perform anywhere near a true 1/4 wave. People I know that have tried these low profile antennas on VHF have been very disappointed, even on receive. You can't take a VHF antenna and shrink it to 3.5 inches and expect it to perform well, the physics just don't work that way.
On transmit, they don't handle much power and are extremely narrow bandwidth. The bandwidth could be tuned just fine for railroad, but the reduce performance due to it's size is going to be disappointing.
Save yourself the money and just get the 1/4 wave whip, you will be much happier. If you are really concerned about the size, get yourself a mag mount with a BNC on it. Purchase a portable radio antenna with a BNC connector, it'll very likely outperform this antenna.