Estimate time lost to traffic delays.
Congestion delay is the difference between your actual journey time and the free-flow time — what the same route takes at 3am. Nineteen minutes each way on ten trips a week is 190 minutes weekly, which annualises to 165 hours, or more than four working weeks. Putting a value on the hour converts that into a figure comparable with the cost of the alternatives: a rail season ticket, moving closer, or shifting your working hours. The number is usually large enough to change a decision, which is precisely why commuters underestimate it — a delay experienced 20 minutes at a time never feels like a month of the year.
Traffic Delay
Delay per trip = actual minutes - free-flow minutes; weekly = delay x trips; annual hours = weekly x 52 / 60; cost = hours x value of time
Check the route in a navigation app at 3am, or use the fastest time it has ever shown you. That is the baseline against which the congestion penalty is measured.
Often dramatically. Congestion is highly non-linear near capacity, so departing 30 minutes earlier can cut a 20-minute delay to almost nothing — the peak is narrower than it feels.