Middleware has emerged as an important architectural component in supporting distributed applications. The role of middleware is to present a unified programming model to application writers and to mask out problems of heterogeneity and distribution. It is motivated by the convergence of the embedded sensor and mobile communication revolutions in the automobile industry. The vehicle fleet is morphing into a vast mobile sensor fleet. The authors provide a middleware architecture and implementation that addresses the needs of a distributed system of mobile sensors comprised of vehicles and intersections producing traffic-related data for traffic safety and operations. The authors discuss the technical challenges that the middleware addresses and describe a prototype implementation. Traffic management, intersection safety and vehicle-to-vehicle safety applications are three applications described and implemented on the middleware. The authors conclude their paper with conducting performance measures that relate to the cost of overhead incurred from using the middleware. The measurements show the middleware is efficient enough for the road safety and congestion relief applications presented.