Relay Posts for Foot Couriers: How Long a Stage Can Be When the Courier Must Also Walk Home

Where no vehicle goes, mail still moves by relay: couriers walk stages between posts, handing the bag onward like a baton. This paper sizes the stage from the courier's day. A courier walks loaded at a stated 3.6 km/h and returns unladen at 4.4 km/h; if the same courier must walk out and back within a seven-hour working day, the longest stage is 13.8 km. A 180 km route then needs 14 stages and 13 intermediate posts at a stated USD 260 a year each — USD 3380.0 a year in posts — and, pipelined with every stage walked daily, moves mail end to end in 14 days, against 7.1 days for a single through-courier walking the whole route with nightly rests. The relay is not faster door-to-door for one bag; its advantage is that it is a service — daily, staffed at both ends, and independent of any one walker's endurance. The paper also prices the alternative stage model, couriers resident at each post walking one-way, which doubles stage length and halves the posts. SIMULATED, NOT MEASURED.