  We present a system to coordinate 'urban mobility swarms' in order to promote
the use and safety of lightweight, sustainable transit, while enhancing the
vibrancy and community fabric of cities. This work draws from behavior
exhibited by swarms of nocturnal insects, such as crickets and fireflies,
whereby synchrony unifies individuals in a decentralized network. Coordination
naturally emerges in these cases and provides a compelling demonstration of
'strength in numbers'. Our work is applied to coordinating lightweight
vehicles, such as bicycles, which are automatically inducted into ad-hoc
'swarms', united by the synchronous pulsation of light. We model individual
riders as nodes in a decentralized network and synchronize their behavior via a
peer-to-peer message protocol and algorithm, which preserves individual
privacy. Nodes broadcast over radio with a transmission range tuned to localize
swarm membership. Nodes then join or disconnect from others based on proximity,
accommodating the dynamically changing topology of urban mobility networks.
This paper provides a technical description of our system, including the
protocol and algorithm to coordinate the swarming behavior that emerges from
it. We also demonstrate its implementation in code, circuity, and hardware,
with a system prototype tested on a city bike-share. In doing so, we evince the
scalability of our system. Our prototype uses low-cost components, and
bike-share programs, which manage bicycle fleets distributed across cities,
could deploy the system at city-scale. Our flexible, decentralized design
allows additional bikes to then connect with the network, enhancing its scale
and impact.
