Introduction
Despite advances in micro mobility and ride sharing, fixed route buses remain the "best way to get the most people around a city efficiently and cheaply". \cite{walker}
A key facet of an efficient fixed-route bus network involves buses maintaining a fixed schedule at fixed bus stops. However, in rapidly urbanizing cities and megacities across the world, increasing congestion increases uncertainty and inefficiencies in bus operations causing unexpected delays and bus-bunching.
Real-Time transit information systems is one such opportunity. Real-time transit which involves tracking the locations of transit and displaying simple information about When the next bus or train is arriving has shown to reduce waiting times at bus stops by 15 percent compared to commuters without such information. \cite{Watkins_2011} Access to real-time transit information has also been linked to overall satisfaction with transit service, increases in ridership, and substantial increases in fare-box revenue. \cite{Brakewood_2015,Tang_2012,Zhang_2008}
If cities could simply increase the practical availability to real-time transit information through common-sense deployment of technology, they could achieve outcomes similar to increases in transit service itself and avoiding a more resource intensive effort.
Encouragingly, with advances in cloud computing and inexpensive hardware, this missing layer of coordination between transit providers and users amounts to a conceptually simple piece of technology. Less encouragingly, legacy technology and a procurement process that prefers complexity often leads to exorbitantly expensive, over-engineered complex systems that create delays and other barriers to service delivery.
NYC’s real-time transit information system, for example, which includes the Metropolitan Transportation Authority's (MTA) BusTime mobile app costs many thousands of dollars per bus.\cite{cubic-transportation-systems2014} In a system that spans well over five thousand buses, the operating costs to simply track a bus's location every 30 seconds can seem difficult to fathom.
Granted that the costs include redundancy and fault-tolerance to ensure that the system operates at all times in a reliable manner.
After a protracted 3 year deployment process, Melbourne, a moderately-sized city, was forced to suspend rollout of its original bus-tracking system in 2013 at only 30% coverage due to unreasonable operating costs.\cite{coyne2014}
To benefit urban residents at massive scales however these implementation and operating costs of real-time transit information are simply not sustainable and must be lowered and offered as an open-source system in the public's interest. It is with these motivations and objectives that we present Bus Lambda so that transit agencies across the world are empowered to implement effective real-time transit-information systems with minimal resources.