Mr Justice Buckley ordered the jury to return not guilty verdicts on David Currie, former head of BR's civil engineering department, and Norbert Jurasek and Michael Brooks, executives of Plasser Railway Machinery (GB), one of BR's main equipment suppliers. All had denied the charges.
Mr Currie, 66, of Penn, Buckinghamshire, was acquitted of taking bribes between 1978 and 1988 from the company and the two executives which the prosecution had alleged included air tickets, champagne and trips to Continental nightclubs.
Mr Jurasek, 51, of Wargrave, Berkshire, Plasser's managing director, Mr Brooks, 64, of Ringwood, Hampshire, the company secretary, and Plasser were cleared of giving bribes. All the defendants were acquitted of plotting to bribe other BR employees.
The prosecution had alleged that bribes were given to encourage BR staff to award contracts to Plasser, which supplied track-laying equipment to BR.
The judge told the jury: 'The evidence simply does not amount or justify the way this case was presented to you.'