It is neither practical nor necessary to replace all of Britain's level crossings following the weekend's fatal crash, Alistair Darling has said.
Opinion is divided over the future of level crossings
The transport secretary was speaking after rail union the RMT called for all unmanned crossings to be replaced.
Mr Darling said the cause of the Berkshire crash would be examined to see if any lessons could be drawn.
But he said there was a limit to what could be done to stop someone who was determined from getting onto the track.
He said Network Rail had already examined individual crossings and some had been replaced.
But he said: "For a lot of these crossings it may not be practical to do something different.
"You've got to bear in mind people can get onto the track anywhere, if they're determined, just as they can onto a busy road if they're really determined to do that.
"We've got to look at these things and think what's a risk and how do we reduce that risk to make the railways as safe as possible."
He said it was possible new technology could be used to prevent future crashes but it would be premature to draw conclusions until the full facts about Saturday's crash had been established.
Gwyneth Dunwoody MP, chairwoman of the Transport Select Committee, said an examination was already taking place into level crossing safety,
She said: "The reality is many of these divide communities and we can't just get rid of them like that.
"It is unrealistic to suggest it and we ought to be looking at whether there are better to ways to stop the train earlier on."
Their comments came after Rail Maritime and Transport union (RMT) leader Bob Crow called for all unmanned crossings on high-speed lines to be scrapped.
But other rail experts dismissed Mr Crow's demand as "ridiculous", saying it would cause many road closures.
The train came to a standstill over 100m from the crossing
Mr Crow, who was calling for an inquiry into rail safety before Saturday's crash, renewed his demands and described the network as "privatised and fragmented".
He said: "The industry must take immediate steps to begin a programme of replacing level crossings with road-bridges or underpasses on all lines carrying high-speed traffic.
"And to undertake a feasibility study with the ultimate aim
of removing all level crossings on Britain's railway network."
A spokeswoman for road safety campaign group Brake agreed, saying the government should invest some of the millions of pounds it collected from motorists each year in replacing level crossings with bridges.
But rail analyst Christian Wolmar accused Mr Crow of making "over the top demands".
He told the BBC: "It's as if you were saying because there are a lot of accidents at traffic lights, traffic lights are too dangerous, and we need to have an overpass or underpass at every traffic light."
And Nigel Harris, editor of Rail magazine, said motorists would "complain bitterly" about road closures.
"Scrapping level crossings on high-speed lines is a ridiculous suggestion. It would shut down many roads," he said.
The Association of Train Operating Companies said getting rid of the crossings would be "hugely challenging".
"There are hundreds of level crossings in use on Britain's railways and there have been very few incidents at these crossings," a spokesman said.
Train drivers' union Aslef, though, suggests an alternative to closure.
Acting general secretary Keith Norman said: "The technology exists to give train drivers advanced warning of blockages on the tracks."
He added: "Simple measures such as closed circuit television
monitored from a local signalling centre could have picked up a vehicle on the crossing."
But Mr Darling said such a system still might not have averted the crash as the driver might not have been able to stop the train in time, even if he had been alerted to the car on the crossing.
Network Rail, responsible for running the railways, says there are currently 7,993 level crossings on the network.
Some 1,700 of these are on public roads and 462 have automatic half barriers, like those used at Ufton Nervet in Berkshire, scene of Saturday's tragedy.
The body has closed 178 crossings over the past two years.