Your ability to set routes may be limited by the presence of diamond junctions (aka diamond crossovers, diamond crossings or flat crossings), so you need to be able to recognize them.
For example, check out the panel below (from Bristol, Modern Era) and work out why you cannot set the following routes before reading the answer in the picture below it.
From 345/347 to 18?
From 22 to 30/32?
From 91/53/51 to 61?
From 265, but not from 65, to 324/326?
In all these cases, no route can be set because diamond junctions do not act as points, i.e., you cannot switch a train from one track to another if they cross in a diamond junction.
Note that diamond junctions are not crossovers. A crossover is a pair of points (switches) that connects two parallel rail tracks, allowing a train on one track to cross over to the other. (Wikipedia ) Note the crossovers below on the Filton lines, also another diamond junction.
Last edited by GeoffM on 15/09/2016 at 03:00