... /GNR I'm interested in, of course. Hi Andrew, For pre-grouping all bets are off. A much-used V-crossing angle at one time was 1:9 (still is in continental Europe). It can be reasonably assumed that 1:9 fixed diamonds and slips were made to match -- and more than assumed for the GER: C. J. Allen (1915) lists angles up to 1:9 for GER obtuse crossings (fixed K-crossings) -- see: obtuse_ger.jpg No doubt the 1:8 rule was arrived at from practical experience of derailments on flatter angles. For GWR in 1943 we have these rules: In radius down to: the flattest angle for a fixed K-crossing is: 60 chains( 3960ft) ....1:8 30 chains( 1980ft) ....1:7.75 20 chains( 1320ft) ....1:7.5 15 chains( 990ft) ....1:7.25 12 chains( 792ft) .. ...