(19)

(11)

EP 0 619 789 A1

(12)

(43) Date of publication: 19.10.1994 Bulletin 1994/42 (21) Application number: 92924779.0 (22) Date of filing: 03.12.1992

(51) International Patent Classification (IPC):  B61L 29/ 22( . ) (86) International application number: PCT/GB1992/002248 (87) International publication number: WO 1993/012963 (08.07.1993 Gazette 1993/16)

(84) Designated Contracting States: IE (30) Priority: 28.12.1991 GB 19910027459 (71) Applicant: BRITISH RAILWAYS BOARD London NW1 1DZ (GB)	(72) Inventors: PARKMAN, William Terence Duffield, Derby DE6 4BX (GB) SUTTON, Malcolm Stuart Borrowash, Derby DE7 3GN (GB) (74) Representative: Sommerville, John Henry, et al  SOMMERVILLE & RUSHTON 11 Holywell Hill St. Albans Hertfordshire, AL1 1EZ St. Albans Hertfordshire, AL1 1EZ (GB)