Those settings are really intended for the use of pakset maintainers, as the pakset is intended to be balanced realistically with default settings. You are of course free to adjust the pakset to your own preferences, but you are then in the realm of modding rather than playing, and the nature of documentation available reflects that fact.
I should note that traffic congestion is a real-world phenomenon that Simutrans-Extended and Pak128.Britain-Ex are intended to simulate at their default settings and that, in reality, the ordinary way of dealing with an excess of demand compared to supply is either to increase the prices or increase the supply, both of which courses of action are open to the player.