P4 (also known as Protofour) is as true to the scale of 4mm to 1ft (1/76 scale) as you can get, giving a true...
You do not always have a model railway controller on you. And even if you do, sometimes you do not have any power socket to use it. This means you may not be able to test an engine before buying it. The easiest solution is to get a 9 volt battery...