I blanked for a solid few seconds and then just started throwing numbers at the wall.
Break the problem into a Fermi estimation: estimate the average number of traffic intersections encountered per day, the average wait time per intersection, and multiply by the number of days in a lifetime. State assumptions clearly, use round numbers, and sanity-check the final figure against a daily or yearly time budget.
Pro tip: Don't just give a number—narrate your reasoning and explicitly call out which assumptions have the biggest impact on the result, then offer a range (e.g., 3–6 months) rather than a single point estimate.
Define what counts as a traffic intersection (traffic lights, stop signs, roundabouts) and whether you're estimating for a global average or a specific region like the US. State that you'll assume a typical adult lifetime of about 80 years.
Estimate how many intersections an average person passes through per day, considering commuting, errands, and leisure. For example, assume 2 commutes per day with 5 intersections each, plus 2 extra trips with 3 intersections each, totaling about 16 intersections per day.
Estimate the average time spent waiting at each intersection, accounting for the fact that not every encounter involves a full stop. For instance, assume an average wait of 20 seconds per intersection, including both stopped and moving-through cases.
Multiply daily encounters by average wait time to get daily waiting time, then multiply by days in a lifetime (80 years × 365 ≈ 29,200 days). Convert the result into hours, days, or months for perspective.
Compare the result to a reasonable daily time budget (e.g., total daily waiting should be a small fraction of the day). Adjust assumptions if needed and present a range (e.g., 3–6 months) to reflect uncertainty.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.