Transport Damage by Vehicle and Road: A Viability Distance for Fragile Produce

A seller carrying fragile produce to a small market faces a choice that is usually made by habit: carry it, cycle it, put it on a cart, or pay for a motor vehicle. This paper replaces habit with arithmetic. For a 20 kg load of firm-ripe tomatoes carried bare in a rigid basket, damage is modelled as D(d) = 1 - exp(-kd), where the rate k is built from a stated count of jolts per kilometre and a stated probability of bruising per jolt, multiplied by a road factor. Five modes are compared on three surfaces. The new result is a viability distance for each combination: the distance at which damage reaches 15%, taken here as the point at which the load stops being worth transporting in that way. On paved road the viability distances are 20.31 km on foot, 13.54 km by pickup, 10.83 km by bicycle, 6.50 km by motorcycle, and 4.64 km by cart. On rough earth they fall to 6.35 km, 4.23 km, 3.39 km, 2.03 km, and 1.45 km respectively. The ranking does not change with the road; only the scale does. Speed, on damage alone, does not protect produce. The gentlest mode is the slowest one, and the unsprung cart is the most damaging mode on every surface examined.