Urban FlowBike messengers are familiar figures in the downtown cores of major cities. Tasked with delivering time sensitive materials within, at most, a few hoursand sometimes in as little as fifteen minutesthese couriers ride in all types of weather, weave in and out of dense traffic, dodging (or sometimes failing to dodge) taxis and pedestrians alike in order to meet their clients' tight deadlines. Riding through midtown traffic at breakneck speeds is