Cities are embracing data-intensive applications to maximize their constrained transportation networks. Platforms such as Google offer route planning services to mitigate the effect of traffic congestion. These use remote servers that require an Internet connection, which exposes data to increased risk of network failures and latency issues. Edge computing, an alternative to centralized architectures, offers computational power at the edge that could be used for similar services. Road side units (RSU), Internet of Things (IoT) devices within a city, offer an opportunity to offload computation to the edge. To provide an environment for processing on RSUs, we introduce RSU-Edge, a distributed edge computing system for RSUs. We design and develop a decentralized route planning service over RSU-Edge. In the service, the city is divided into grids and assigned an RSU. Users send trip queries to the service and obtain routes. For maximum accuracy, tasks must be allocated to optimal RSUs. However, this overloads RSUs, increasing delay. To reduce delays, tasks may be reallocated from overloaded RSUs to its neighbors. The distance between the optimal and actual allocation causes accuracy loss due to stale data. The problem is identifying the most efficient allocation of tasks such that response constraints are met while maintaining acceptable accuracy. We created the system and present an analysis of a case study in Nashville, Tennessee that shows the effect of our algorithm on route accuracy and query response, given varying neighbor levels. We find that our system can respond to 1000 queries up to 57.17% faster, with only a model accuracy loss of 5.57% to 7.25% compared to using only optimal grid allocation. INDEX TERMS Distributed computing, Middleware, Transportation, Vehicle routing, Road side units I. INTRODUCTION Urban cities are growing at a rapid pace. This growth, bolstered by businesses, commerce, and opportunities, is bringing more and more people into these urban landscapes, putting a strain on the cities' limited infrastructure. For example, roads are faced with an influx of motorists resulting in heavy traffic, which makes living in cities unbearable. To meet the growing demands, cities and private companies are turning to data-intensive applications to make the most out of the limited resources. Companies such as Google, Apple, and Waze 1 created traffic-aware navigation apps that leverage crowd-sourced information and cloud environments. These applications allow users access to up-to-date routing information for their daily commutes. 1 https://www.waze.com/ Cloud environments running on centralized architectures can process data effectively for existing services, however, future use cases such as autonomous vehicles have their own challenges [1], such as requiring ultra-reliable low-latency communications [2]. These requirements expose the limitations of the cloud and call for a new architecture that better fits the requirements for real-time analysis and processing of city-level data. One way to resolve ...