Points, sidings and passing loops: getting two trains running
One loop is a train going round. Two trains need somewhere to be out of each other’s way, and that is what points are for. DUPLO points are a wye with a lever; BRIO’s are a straight with a curve grafted on. Either way, the spare arm has to lead somewhere.
A siding
The simplest use of points: the spare arm curves off, a curve the other way brings it parallel to the line, straights run on, and a buffer stop ends it. A train can be parked there while the other runs round. Without the stop the layout has an open joint, and the planner will not offer it.
A passing loop
Two sets of points facing each other along a side, joined by a second road: a train waits on one road while the other passes. In DUPLO this closes exactly; in BRIO the road wants to be 4.6 mm shorter than any straight allows, which is why the BRIO guide says through roads need the middle straight that BRIO no longer makes.
A balloon loop
One set of points whose two arms are joined into a loop. A train runs in at the toe, round, and comes back out facing the other way: it has turned round without reversing. The 59-piece Maxim sheet hangs one off a bigger layout; on its own, in BRIO, four short curves and one large one close the loop within a third of a millimetre where five large ones cannot.
Two loops sharing a road
Facing points on a loop with a road between their spare arms make a second loop that shares part of the first. The 100-piece Maxim sheet climbs that road over the other on ascending tracks. The planner builds this kind for any box with two switches, and cuts the sheet’s own version down to fit a smaller one.