The great thing about railway sleepers, and also what makes them ideal for garden decking, is that they are made of high quality timber, and that even though that is the case, you can get them cheaply. We know they are high quality because they need to be able to withstand the stresses of a train going over them, so they will be made of strong wood which can easily bear the weight of a couple of hundred kilograms. With a garden decking, this is very important, as it will need to be able to withstand the weight of multiple people congregating on top of it.
While this is the main benefit of using railway sleepers, they also offer other advantages in the construction of a garden decking. Their thickness ensures safety, but it also ensures that the product won’t rot away in a couple years, and you will have to replace panels only very rarely.