Estimate extra time from transfers.
A transfer costs more than the wait shown on the timetable. There is the walk between platforms, the scheduled wait, and then a probabilistic component: if there is a 15% chance of missing the connection and services run every 12 minutes, the expected additional delay is 1.8 minutes per transfer. Adding that risk term is what explains why passengers dislike transfers far more than the scheduled minutes suggest — the penalty is not just the average, it is the variance. This is why transport planners apply a transfer penalty of 5 to 15 minutes per interchange when comparing routes, and why a slower direct service often beats a faster connecting one.
Transfer Penalty
Scheduled = transfers x (wait + walk); expected miss penalty = transfers x miss probability x headway; total = scheduled + miss penalty
Because of the risk, not the average. A missed connection costs a whole headway, so the possible outcomes are widely spread — and travellers weight that uncertainty heavily.
Usually yes, up to 5-15 minutes per transfer avoided. On low-frequency services with a long headway, a direct route can be worth much more than that.