The quango said the aim could be achieved only by closing all the UK's level crossings, adding that was a "challenge society is unlikely to be able to afford".
Nine people were killed on level crossings in Britain in 2012/13. Last month Louise Ellman MP, the chairwoman of the Commons Transport Select Committee, described every one of those deaths as "a tragedy which could have been averted".
A report by the committee called for an aim of "no level crossing fatalities by 2020".
But in its response yesterdayNetwork Rail said: "The solution to eliminating risk completely would of course be to close all crossings but this is a challenge society is unlikely to be able to afford and the resources needed would be disproportionate when compared with addressing the risks facing the public on the road network, for example."
The organisation added that if the railways were being built today "it would be inconceivable that society would tolerate the construction of level crossings, particularly those where a pedestrian could encounter trains travelling at speeds greater than cars are allowed to travel on our roads".
There are around 6,400 level crossings in the UK, and hundreds in Scotland.
Network Rail said that they were a legacy from when rail meant "an occasional slow steam train".
But it said that the risks associated with using level crossings in Britain were lower than across most European countries.
A number of collisions have highlighted the dangers of open level crossings, including the deaths of Angus and Margaret MacKay, both 81, and Angus's brother Donald, 66, at the Halkirk crossing in Caithness in 2009.